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PUBLICLY AVAILABLE
SPECIFICATION
IEC PAS 61975
Pre-Standard First edition2004-08
System tests for high-voltagedirect current (HVDC) installations
Reference number
IEC/PAS 61975:2004(E)
C o p y r i gh t e d m a t er i al l i c en s e d t oE l e c t r i c i t y of V i e t n am b y T h om s on S c i en t i f i c ,I n c
. ( www. t e c h s t r e e t . c om ) .T h i s c o p y d ownl o
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Publication numbering
As from 1 Janua ry 1997 al l IEC publ icati ons are issued wi th a des ignat ion in the60000 series. For example, IEC 34-1 i s now referred to as IEC 60034-1.
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The IEC is now publishing consolidated versions of its publications. For example,edition numbers 1.0, 1.1 and 1.2 refer, respectively, to the base publication, thebase publication incorporating amendment 1 and the base publication incorporatingamendments 1 and 2.
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. ( www. t e c h s t r e e t . c om ) .T h i s c o p y d ownl o
a d e d on2 0 1 4 - 0 1 - 0 6 0 8 : 2 8 : 2 8 - 0 6 0 0 b y a u t h or i z e d u s er P h am V an c h i .
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PUBLICLY AVAILABLESPECIFICATION
IEC PAS 61975
Pre-Standard First edition2004-08
System tests for high-voltagedirect current (HVDC) installations
PRICE CODE
IEC 2004 Copyright - all rights reserved
No part of this publication may be reproduced or utilized in any form or by any means, electronic ormechanical, including photocopying and microfilm, without permission in writing from the publisher.
International Electrotechnical Commission, 3, rue de Varembé, PO Box 131, CH-1211 Geneva 20, Switzerland
Telephone: +41 22 919 02 11 Telefax: +41 22 919 03 00 E-mail: inmail@iec.ch Web: www.iec.ch
XGFor price, see current catalogue
Commission E lectrotechnique InternationaleInternational Electrotechnical Com mission
C o p y r i gh t e d m a t er i al l i c en s e d t oE l e c t r i c i t y of V i e t n am b y T h om s on S c i en t i f i c ,I n c
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a d e d on2 0 1 4 - 0 1 - 0 6 0 8 : 2 8 : 2 8 - 0 6 0 0 b y a u t h or i z e d u s er P h am V an c h i .
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– 2 – PAS 61975 © IEC:2004 (E)
CONTENTS
Part 0: Executive Summary......................................................................... 4
Part 1: General........................................................................................... 11
1.1 Statement of Purpose ...................................................................... 131.2 Structure of the HVDC System......................................................... 151.3 Structure of the Control and Protection System................................ 161.4 Logical Steps of Commissioning ...................................................... 171.5 Structure of System Testing............................................................. 19
Part 2: Off-Site Tests ................................................................................. 20
2.1 Steady State Performance of the Controls ....................................... 232.1.1 Measurements................................................................................. 242.1.2 Control and Protective Sequences................................................... 242.1.3 Steady Stale Performance Tests...................................................... 252.2 Dynamic Performance Tests............................................................ 272.2.1 Controls-Step Responses ................................................................ 292.2.2 Control Mode Transfer..................................................................... 312.2.3 AC System Interaction/Control......................................................... 332.2.4 Commutation Failures and Valve Misfires ........................................ 34
2.2.5 AC Filter, Transformer and Reactive Element Switching.................. 362.2.6 AC and DC System Faults ............................................................... 372.2.7 Islanding ......................................................................................... 412.3 Functional Performance Tests ......................................................... 432.4 Type Tests on the Control and Protection Equipments .................... 46
Part 3: Converter Tests ............................................................................. 50
3.1 Converter Unit Tests ....................................................................... 523.2 Converter Station Tests................................................................... 54
3.2.1 HV Energization or AC Filters, Capacitor Banks and Shunt Reactors .. 543.2.2 Open Line Test of the DC Switchyard.............................................. 553.2.3 Load Tests..................................................................................... 573.3 Open Line Tests on the DC Transmission Circuit...... ......... ......... ..... 61
Part 4: End-to-End-Tests........................................................................... 63
4.1 Changing the DC System Configuration, Off Voltage ....................... 674.2 Start and Stop Sequences and Steady State Operation at Minimum Power...................................................................................................... 69
4.3 Protective Blocking and Tripping Sequences ................................... 734.4 Power and Current Ramping ........................................................... 764.5 Reduced Voltage Operation............................................................. 78
C o p y r i gh t e d m a t er i al l i c en s e d t oE l e c t r i c i t y of V i e t n am b y T h om s on S c i en t i f i c ,I n c
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PAS 61975 © IEC:2004 (E) – 3 –
Part 5: Steady-State Performance and Interference Tests....................... 81
5.1 Harmonic Performance and Filter Components Rating ..................... 835.2 Audible Noise.................................................................................. 865.3 Overload/Temperature Rise ............................................................ 88
5.4 Interference .................................................................................... 905.5 Earth Electrode................................................................................ 92
Part 6: Operation and Integration Tests .................................................... 9
6.1 Changes of DC Configuration.......................................................... 986.1.1 Tests from Monopolar Metallic Return Operation............................ 1006.1.2 Tests from Monopolar Earth Return Mode...................................... 1016.1.3 Tests from Bipolar Operation ......................................................... 1016.2 Control Performance...................................................................... 103
6.2.1 Step Response .............................................................................. 1056.2.2 Control Mode Transfer................................................................... 1106.2.3 AC System Interaction / Control..................................................... 1136.2.4 Commutation Failure ..................................................................... 1166.3 Switching AC Side Fillers and Transformers................................... 1196.4 Loading Tests................................................................................ 1216.5 AC and DC System Staged Fault Tests.......................................... 1246.6 Loss of Telecommunications, Auxiliaries, or Redundant Equipment 1296.6.1 Loss of Telecommunications between Terminals ........................... 1296.6.2 Loss of Auxiliary Power Supplies ................................................... 1326.6.3 Loss of Redundant Equipment....................................................... 134
Part 7: Trial Operation............................................................................. 135
Part 8: System Test Plan and Documentation....................................... 138
8.1 Plant Documentation and Operating Manuals ................................ 1398.2 System Study Reports and Technical Specifications ...................... 1398 3 Inspection and Test Plan ............................................................... 1398.4 System Test Program.................................................................... 1418.5 Test Procedures for each Test....................................................... 1428.6 Documentation of System Test Results.......................................... 1428.7 Deviation Reports .......................................................................... 143
C o p y r i gh t e d m a t er i al l i c en s e d t oE l e c t r i c i t y of V i e t n am b y T h om s on S c i en t i f i c ,I n c
. ( www. t e c h s t r e e t . c om ) .T h i s c o p y d ownl o
a d e d on2 0 1 4 - 0 1 - 0 6 0 8 : 2 8 : 2 8 - 0 6 0 0 b y a u t h or i z e d u s er P h am V an c h i .
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– 4 – PAS 61975 © IEC:2004 (E)
INTERNATIONAL ELECTROTECHNICAL COMMISSION ____________
SYSTEM TESTS FOR HIGH-VOLTAGE DIRECT CURRENT (HVDC)INSTALLATIONS
FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprisingall national electrotechnical committees (IEC National Committees). The object of IEC is to promoteinternational co-operation on all questions concerning standardization in the electrical and electronic fields. Tothis end and in addition to other activities, IEC publishes International Standards, Technical Specifications,Technical Reports, Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IECPublication(s)”). Their preparation is entrusted to technical committees; any IEC National Committee interestedin the subject dealt with may participate in this preparatory work. International, governmental and non-governmental organizations liaising with the IEC also participate in this preparation. IEC collaborates closelywith the International Organization for Standardization (ISO) in accordance with conditions determined by
agreement between the two organizations.2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
consensus of opinion on the relevant subjects since each technical committee has representation from allinterested IEC National Committees.
3) IEC Publications have the form of recommendations for international use and are accepted by IEC NationalCommittees in that sense. While all reasonable efforts are made to ensure that the technical content of IECPublications is accurate, IEC cannot be held responsible for the way in which they are used or for anymisinterpretation by any end user.
4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publicationstransparently to the maximum extent possible in their national and regional publications. Any divergencebetween any IEC Publication and the corresponding national or regional publication shall be clearly indicated inthe latter.
5) IEC provides no marking procedure to indicate its approval and cannot be rendered responsible for anyequipment declared to be in conformity with an IE C Publication.
6) All users should ensure that they have the latest edition of this publication.
7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts andmembers of its technical committees and IEC National Committees for any personal injury, property damage orother damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) andexpenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IECPublications.
8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications isindispensable for the correct application of this publication.
9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject ofpatent rights. IEC shall not be held responsible for i dentifying any or all such patent rights.
A PAS is a technical specification not fulfi ll ing the requirements for a standard but madeavailable to the public.
IEC-PAS 61975 was submitted by the CIGRÉ (International Council on Large ElectricSystems) and has been processed by subcommittee 22F: Power electronics for electricaltransmission and distribution systems, of IEC technical committee 22: Power electronic systemsand equipment.
The text of this PAS i s based on thefollowing document:
This PAS was approved forpublication by the P-members of thecommittee concerned as indicated in
the following document
Draft PAS Report on voting
22F/96/NP 22F/101/RVN
Following publication of this PAS, which is a pre-standard publication, the technical committeeor subcommittee concerned will transform it into an International Standard.
C o p y r i gh t e d m a t er i al l i c en s e d t oE l e c t r i c i t y of V i e t n am b y T h om s on S c i en t i f i c ,I n c
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PAS 61975 © IEC:2004 (E) – 5 –
An IEC-PAS licence of copyright and assignment of copyright has been signed by the IEC andCIGRÉ and is recorded at the Central Office.
This PAS shall remain valid for an initial maximum period of three years starting from 2004-08. The validity may be extended for a single three-year period, following which it shall be
revised to become another type of normative document or shall be withdrawn.
C o p y r i gh t e d m a t er i al l i c en s e d t oE l e c t r i c i t y of V i e t n am b y T h om s on S c i en t i f i c ,I n c
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– 6 – PAS 61975 © IEC:2004 (E)
PART 0: EXECUTIVE SUMMARY
Abstract
This document which gives guidance on all aspects of system tests for HVDC
installations (excluding multiterminal HVDC systems), has been prepared by
CIGRE WG 14.12. It is structured in eight parts.
The guide should give potential users guidance, regarding which course of
action should be taken in planning commissioning activities.
Structure of the tests and a brief statement of the purpose of the individual group
of tests is presented.
Introduction
Commissioning an HVDC system is a very complex task which may affect more
than the actual contract parties. The complexity and the diversified areas of
concern during system testing require thorough planning and scheduling,
cooperation of all parties involved, and complete and structured documentation.
System testing completes commissioning of an HVDC system.
It allows the supplier to verify the suitability of the station equipment installed
and the functional completeness of the system; adjustments and optimization
can be made.
The user is shown that the requirements and stipulations in the contract are met
and that there is correlation with studies and previous off-site testing.
C o p y r i gh t e d m a t er i al l i c en s e d t oE l e c t r i c i t y of V i e t n am b y T h om s on S c i en t i f i c ,I n c
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PAS 61975 © IEC:2004 (E) – 7 –
In adapting the HVDC system to the "real world" (the connected AC systems)
various constraints may exist, which require coordination within the economic
schedules of the AC system operators.
System testing proves to the public that tolerable values of phenomena
concerning public interest are not exceeded.
Five (5) major aspects are subject to system testing:
- HVDC station equipment and DC line/cable/bus incl. earth electrode, if any
- HVDC controls and protection
- Environmental considerations
- AC/DC system interaction
- System performance
The following diagram shows the interrelation between these aspects:
C o p y r i gh t e d m a t er i al l i c en s e d t oE l e c t r i c i t y of V i e t n am b y T h om s on S c i en t i f i c ,I n c
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– 8 – PAS 61975 © IEC:2004 (E)
Acceptance tests shall be defined between supplier and user in advance and
may be performed at an appropriate time during the test schedule.
The testing sequence is best scheduled starting at local level with simple tests
before Involving additional locations and the transmission system and more
complex tests,
A system test plan has proven itself as a good means for planning and
scheduling.
Complete and organized documentation of the system tests is to the benefit ofboth the supplier and the user, it shall form part of the project documentation
and contain al! necessary oscillograms, logs, etc, and if necessary a
commentary and references.
Structure of System Testing
System testing should follow the structure of the HVDC system, starting from the
smallest, least complex operational unit and shall end with the total system in
operation.
The first step, to ensure proper function, is to debug and to test the control
system during off-site tests. Because of the complex nature of the HVDC
system, this requires a simulator. Where applicable it is recommended to run
commissioning tests and acceptance tests during the off-site tests in a similar
way to those performed later at site. In such a way off-site tests can serve as
reference for the site tests.
C o p y r i gh t e d m a t er i al l i c en s e d t oE l e c t r i c i t y of V i e t n am b y T h om s on S c i en t i f i c ,I n c
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PAS 61975 © IEC:2004 (E) – 9 –
System Tests for HVDC Installations
Before system commissioning can begin at site, preconditions concerning
subsystem tests, operator training and safety Instructions, system test plan and
test procedures, and all necessary test equipment must be fulfilled.
After all preconditions are fulfil led, each converter unit is commissioned
separately during the converter unit test. Open-circuit tests and/or short-circuit
tests are possible for this purpose. Converter station tests also include
energization of the AC filter, DC yard energization and back-to-back tests.
Back-to-back tests allow full active power with the nominal DC voltage, firing
angles, harmonics, etc. whilst still disconnected from the second AC system.Certain control, relaying and instrumentation changes as welt as temporary DC
switchyard changes may be required for back-to-back tests.
Before end-:o-end tests are performed, it is advisable to perform an open line
test and shorted line tests with the DC transmission line. This test can be
repeated from both ends to verify the integrity of the DC line.
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– 10 – PAS 61975 © IEC:2004 (E)
End-to-end tests involve both stations and the transmission Tine. With this
operation, power is transmitted for the first time. This test usually start on a
monopolar basis, with full bipolar operation being the final step.
Having the complete system running properly, steady state verification tests can
be performed. With normal operating ramp settings and automatic switching
sequences in place the effect of a number of disturbances on the DC side of the
system as well as in the AC systems may be checked.
Operation and Integration tests verify the transient and fault recovery behaviour
of the HVDC system-Correct operation of the HVDC system over an extendedperiod of time is checked during the trial operation.
The HVDC system tests are now completed, all functions have been verified and
the HVDC system is ready to be handed over to the owners. The acceptance
tests necessary to verify whether acceptance criteria have been met may have
been performed all or in part during the commissioning period.
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PAS 61975 © IEC:2004 (E) – 11 –
PART 1: GENERAL
Introduction
This document deals with all aspects of system tests of HVDC systems. System
tests start when all relevant subsystems have been precommissioned and are
ready for operation. They end with full acceptance of the system for operation in
the power systems.
This document provides background information for IEC to produce standards
for system testing. It is structured in eight parts:
1. General
2. Off-site Tests
3. Converter Tests
Commissioning of converter units, verification of steady state performance
of units, switching tests
- converter unit tests
- converter station tests.
4. End-to-End Tests
Commissioning of the transmission system, verification of station
coordination.
5. Steady-State Performance and Interference Tests
Verification of steady-state performance and interference caused by the
HVDC-system.
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– 12 – PAS 61975 © IEC:2004 (E)
6. Operation and Integration Tests
Operational and fault tests, verification of dynamic performance and
interaction between the DC and AC systems.
7. Trial operation
8. System test plan and documentation
The guide also covers interrelation with off-site system tests. Preconditions of
system tests wit] be established.
Part 1 General will address the purpose of this document, the HVDC systemstructure, the control and protection structure, the logical steps of commissioning
and the structure of system testing of HVDC system. Parts 2 to 7 comprise
individual paragraphs on general test objectives, information on test procedures,
as well as detailed descriptions of the individual tests, including as appropriate
the following;
- Specific objectives per test
- Test procedures
- Test acceptance criteria
- Preconditions for the test
- References to system studies/specifications
- References to off-site tests
- Special conditions
Part 8 describes the documentation normally required to adequately perform the
system tests. This primarily consists of the following:
- Plant documentation
- Inspection and test plan (ITP)
- System study reports/technical specifications
- System test program
- Test procedures for each test
- Documentation of system test results
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PAS 61975 © IEC:2004 (E) – 13 –
- Deviation report
The guide should give potential users guidance, regarding which course of
action should be taken in planning commissioning activities. The tests described
in the guide may not be applicable to all projects, but represent a range of
possible tests which should be considered.
1.1 Statement of Purpose
System testing completes the commissioning of an HVDC system.
It allows the supplier to verify the suitability of the station equipment installed
and the functional completeness of the system; adjustments and optimizationcan be made.
The user is shown that the requirements and stipulations in the contract are met
and that there is correlation with studies and previous off-site testing.
For the user, the completion of system testing marks the beginning of
commercial operation of the HVDC system.
In adapting the HVDC system to the "real world" (the connected AC systems)
various constraints may exist, which require coordination within the economic
schedules of the AC system operators.
System testing proves to the public that tolerable values of phenomena
concerning public interest are not exceeded.
Five (5) major aspects are subject to system testing:
- HVDC station equipment and DC line/cable/bus incl. earth electrode, if any
- HVDC controls and protection
- Environmental considerations
- AC/DC system interaction –
- System performance
C o p y r i gh t e d m a t er i al l i c en s e d t oE l e c t r i c i t y of V i e t n am b y T h om s on S c i en t i f i c ,I n c
. ( www. t e c h s t r e e t . c om ) .T h i s c o p y d ownl o
a d e d on2 0 1 4 - 0 1 - 0 6 0 8 : 2 8 : 2 8 - 0 6 0 0 b y a u t h or i z e d u s er P h am V an c h i .
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The following diagram shows the interrelation between these aspects:
Thorough and complete system testing of the above components can be
achieved with the tests described in the eight parts of the guide.
Acceptance tests shall be defined between supplier and user in advance and
may be performed at an appropriate time during the test schedule.
System testing may affect more than the actual contract parties. Those parties
shall be informed in time.
The complexity and the diversified areas of concern during system testing
require thorough planning and scheduling, cooperation of all parties involved, as
well as complete and organized documentation.
The testing sequence is best scheduled starting at local level with simple tests
before involving additional locations and the transmission system and more
complex tests. A system test plan (probably as part of a site test plan) has
proven itself as a good means for planning and scheduling.
C o p y r i gh t e d m a t er i al l i c en s e d t oE l e c t r i c i t y of V i e t n am b y T h om s on S c i en t i f i c ,I n c
. ( www. t e c h s t r e e t . c om ) .T h i s c o p y d ownl o
a d e d on2 0 1 4 - 0 1 - 0 6 0 8 : 2 8 : 2 8 - 0 6 0 0 b y a u t h or i z e d u s er P h am V an c h i .
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PAS 61975 © IEC:2004 (E) – 15 –
Complete and organized documentation of the system tests is to the benefit of
both the supplier and the user, it shall form part of the project documentation
and contain all necessary oscillograms, logs, etc., and if necessary a
commentary and references.
1.2 Structure of the HVDC System
From a functional point of view an HVDC system consists of a sending terminal
and a receiving terminal, each connected to an AC-system. The two terminals
have one or several converters connected in series on the DC side and in
parallel on the AC side. The terminals are connected by a transmission line or
cable or a short piece of busbar (Back-to-Back station). Multiterminal systems
are not addressed in this document
C o p y r i gh t e d m a t er i al l i c en s e d t oE l e c t r i c i t y of V i e t n am b y T h om s on S c i en t i f i c ,I n c
. ( www. t e c h s t r e e t . c om ) .T h i s c o p y d ownl o
a d e d on2 0 1 4 - 0 1 - 0 6 0 8 : 2 8 : 2 8 - 0 6 0 0 b y a u t h or i z e d u s er P h am V an c h i .
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1.3 Structure of the Control and Protection System
Each of the converter units can be controlled individually. To make the system
function as a transmission system the converter units should be controlled in acoordinated way by a second level of the control system. Coordinated controls
and protection are essential for the proper function of HVDC systems.
C o p y r i gh t e d m a t er i al l i c en s e d t oE l e c t r i c i t y of V i e t n am b y T h om s on S c i en t i f i c ,I n c
. ( www. t e c h s t r e e t . c om ) .T h i s c o p y d ownl o
a d e d on2 0 1 4 - 0 1 - 0 6 0 8 : 2 8 : 2 8 - 0 6 0 0 b y a u t h or i z e d u s er P h am V an c h i .
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PAS 61975 © IEC:2004 (E) – 17 –
1.4 Logical Steps of Commissioning
System commissioning should follow the structure of the HVDC system, starting
from the smallest, least complex operational unit, usually a 12-pulse converter,and shall end with the total system in operation.
The first step, to ensure proper function, is to debug and test the control system
during factory system tests. Because of the complex nature of the HVDC
system, this requires a simulator. Where applicable, it is recommended to run
commissioning tests and acceptance tests in addition to ail limiting design cases
on the simulator in a similar way to those done later at site. In such a way
simulator tests can serve as reference for the site tests.
Before system commissioning can begin at site the following preconditions
should be fulfilled.
- All subsystems tested and commissioned including AC filters and the
converter transformers with special attention to possible transformer/AC filter
resonance during energizing
- Sufficient training of operating personnel- Operating instructions for the station available to the operators
- Personnel, plant safety and security instructions made
- System test plan and documentation (part 8) ready and agreed upon
- AC/DC power profiles agreed for each test
- Any AC/DC system operating restrictions identified
- Operator voice communications available
- All necessary test equipment calibrated and operational
- Procedures for the preparation and evaluation of test results agreed upon
After all preconditions are fulfil led, each converter unit is commissioned
separately. Open-circuit tests and/or short-circuit tests are possible for this
purpose. Steady-state performance and interference tests may start at this
instant; however, they can be performed one by one at any convenient other
place dying the system test program, in order to minimize duplication of tests.
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. ( www. t e c h s t r e e t . c om ) .T h i s c o p y d ownl o
a d e d on2 0 1 4 - 0 1 - 0 6 0 8 : 2 8 : 2 8 - 0 6 0 0 b y a u t h or i z e d u s er P h am V an c h i .
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If possible, as a next step the converters in each station should be connected
back-to-back. This allows full active power with the nominal DC voltage, firing
angles, harmonics, etc. whilst still disconnected from the second AC system.
Certain control, relaying and instrumentation changes as well as temporary DC
switchyard changes may be required for back-to-back tests.
Before full end-to-end tests are performed, it is advisable to perform an open line
test and shorted line tests with the DC transmission line. This test can be
repeated from both ends to verify the integrity of the DC line.
End-to-end tests will then be conducted. These tests involve both stations and
the transmission line. With this operation power is transmitted for the first time.
This test is usually done on a monopolar basis first, with full bipolar operating
being the final step.
Having the complete system running properly in steady state operation, with
normal operating ramp settings and automatic switching sequences in place the
effect of a number of disturbances on the DC side of the system as well as in the
AC systems may be checked. Operation and integration tests verify the transient
and fault recovery behaviour of the HVDC system.
The HVDC system tests are now completed, all functions have been verified and
the HVDC system is ready to be handed over to the owners. The acceptance
tests necessary to verify whether acceptance criteria have been met may have
been performed all or In part during the commissioning period- To avoid
unnecessary duplication of such tests, careful consideration should be given in
advance as to when acceptance tests are carried out.
If acceptance tests are still outstanding or acceptance tests have to be repeated
due to modifications they should be performed at this time, or following trial
operation, as appropriate.
Finally it has to be ensured that the system also operates correctly over an
extended period of time. This is checked during the trial operation.
C o p y r i gh t e d m a t er i al l i c en s e d t oE l e c t r i c i t y of V i e t n am b y T h om s on S c i en t i f i c ,I n c
. ( www. t e c h s t r e e t . c om ) .T h i s c o p y d ownl o
a d e d on2 0 1 4 - 0 1 - 0 6 0 8 : 2 8 : 2 8 - 0 6 0 0 b y a u t h or i z e d u s er P h am V an c h i .
N of ur t h er r e pr o d u c t i on or d i s t r i b u t i oni s p er mi t t e d .
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1.5 Structure of System Testing
C o p y r i gh t e d m a t er i al l i c en s e d t oE l e c t r i c i t y of V i e t n am b y T h om s on S c i en t i f i c ,I n c
. ( www. t e c h s t r e e t . c om ) .T h i s c o p y d ownl o
a d e d on2 0 1 4 - 0 1 - 0 6 0 8 : 2 8 : 2 8 - 0 6 0 0 b y a u t h or i z e d u s er P h am V an c h i .
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PART 2: OFF-SITE TESTS
General
Introduction
This part describes the testing of the control equipment prior to it being shipped
to site. The following tests are outlined:
2.1 Steady state performance of the controls
2.2 Dynamic performance tests
2.3 Functional performance tests
2.4 Type tests on the control and protection equipments
Subsequent to the Routine Testing of the HVDC-System Control and Protection
equipment it is normal practice to check the steady state, the functional and the
dynamic performance of this equipment prior to it being shipped to site. Thesetests provide the opportunity to set up the parameters of the control circuits
(though these set tings may have to be fine tuned later at site) and to obtain a
preliminary check on the performance of the equipment relative to the specified
requirements.
Performance of the protective functions of the converter, during various
simulated faults, can also be checked. This enables the equipment to be partly
commissioned off-site. It also provides the opportunity to detect and correct
hardware and software errors or deficiencies in the control and protection
systems.
C o p y r i gh t e d m a t er i al l i c en s e d t oE l e c t r i c i t y of V i e t n am b y T h om s on S c i en t i f i c ,I n c
. ( www. t e c h s t r e e t . c om ) .T h i s c o p y d ownl o
a d e d on2 0 1 4 - 0 1 - 0 6 0 8 : 2 8 : 2 8 - 0 6 0 0 b y a u t h or i z e d u s er P h am V an c h i .
N of ur t h er r e pr o d u c t i on or d i s t r i b u t i oni s p er mi t t e d .
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PAS 61975 © IEC:2004 (E) – 21 –
To carry out the dynamic performance tests it is necessary to have a real time
HVDC simulator which includes representation of the AC systems, AC filters,
converter equipment, DC smoothing reactors, DC lines and DC filters. The
extent of the system representations should be sufficient to replicate resonances
as determined from previous studies. In general, a comprehensive simulation will
enable thorough fault tracing to be done and allow effective commissioning at
site.
As defined in Part 1 of this guide the control equipment is arranged in a
hierarchical structure and only the representative sections which will affect the
dynamic performance would be used for the dynamic tests. These controls would
be the closed loop control sections of the HVDC System Controls (Master
Control), Station Control, Pole Controls and Converter Control. The
telecommunication system and the valve base electronics would be appropriate.
The Valve Base Electronics would be appropriately simulated. Conventional
protection equipment would be omitted i.e. that for AC filters, DC filters and
converter transformers but the protection for the DC system would be included.
The control equipment as defined above needs not necessarily be that supplied
for the contract.
The real time simulator may also be used for the functional performance tests
but other forms of simulation e.g. by software models, are possible. For the
functional performance tests the complete control system shall be tested. Fault
recorders and Sequence of Event Recorders which are "stand alone
equipments" may not be included for the Functional Performance Tests. If these
recorders are not used the validity of output signals to these equipments wouldbe checked during the tests.
Finding and correcting hardware and software errors in the control system is an
important function of off-site testing. Such faults are easier to find and correct
off-site rather than during commissioning. Correcting such faults reduces the
probability of disturbing the Customers' power system during site commissioning.
C o p y r i gh t e d m a t er i al l i c en s e d t oE l e c t r i c i t y of V i e t n am b y T h om s on S c i en t i f i c ,I n c
. ( www. t e c h s t r e e t . c om ) .T h i s c o p y d ownl o
a d e d on2 0 1 4 - 0 1 - 0 6 0 8 : 2 8 : 2 8 - 0 6 0 0 b y a u t h or i z e d u s er P h am V an c h i .
N of ur t h er r e pr o d u c t i on or d i s t r i b u t i oni s p er mi t t e d .
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– 22 – PAS 61975 © IEC:2004 (E)
The principles for off-site testing of the control system are as follows:
a) Controls, as defined above, should be present and connected in an identical
manner to the final site configuration. Possible exceptions are simple interfaceequipment, Fault Recorders and Sequence of Events Recorders.
b) It is desirable that the test team acts independently from the equipment
design team to verify correct operation of the control system. The test team
shall include representatives from the commissioning group, the design
group and the test group. It is recommended that the customer takes a
significant role in this testing team in order to provide valuable experience
in training customers staff.
c) During the test period the equipment being tested shall be under the control
of the test team leader and no changes should be made without his
approval. Changes to the equipment should be recorded in conformity with
the defined Quality Assurance (QA) procedures, thus ensuring that the
tests are carried out on a known state of hardware and software.
d) An off-site test plan including AC system representations, DC configurations
and tests to be performed shall be mutually agreed between the manufacturer
and the customer in advance of the commencement of the tests.
Type testing, if required, can be carried out to demonstrate performance over the
specified environment, with variations of power supply voltage and simulation of
faults on auxiliary systems, to demonstrate the stability of the control and the
accuracy of protection settings. In addition it may be possible to demonstrate
interference immunity of the control and protection equipment, together with the
communication interface.
General Test Objectives
1. To check the steady state, the functional and the dynamic performance
of the control equipment and, if required, to carry out some of the type
tests for the control and protection equipment,
2. To make preliminary settings of the control parameters.
C o p y r i gh t e d m a t er i al l i c en s e d t oE l e c t r i c i t y of V i e t n am b y T h om s on S c i en t i f i c ,I n c
. ( www. t e c h s t r e e t . c om ) .T h i s c o p y d ownl o
a d e d on2 0 1 4 - 0 1 - 0 6 0 8 : 2 8 : 2 8 - 0 6 0 0 b y a u t h or i z e d u s er P h am V an c h i .
N of ur t h er r e pr o d u c t i on or d i s t r i b u t i oni s p er mi t t e d .
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PAS 61975 © IEC:2004 (E) – 23 –
3. To provide confirmation of the design specifications and study results for
the control and protection equipment and also to provide test data for
comparison with that obtained during the operation and integration tests
defined in PART 6 of the guide.
4. To find and correct errors and deficiencies in the control and protection
hardware and software.
Preconditions for the Tests
1. For the functional performance tests the control and protection
equipment shall have passed all its routine tests.
2. For the functional performance tests the control and protection cubicles
shall be interconnected In the "as site" configuration.
3. An off-site test plan including AC system representations, DC
configurations and tests to be performed shall be mutually agreed
between the manufacturer and the customer in advance of the
commencement of the tests.
4. The studies defining the control strategies shall have been completed.
2.1 Steady State Performance of the Controls
Introduction
Before the functional and the dynamic performance test can be performed, the
steady state performance of the control equipment shall have been
demonstrated.
C o p y r i gh t e d m a t er i al l i c en s e d t oE l e c t r i c i t y of V i e t n am b y T h om s on S c i en t i f i c ,I n c
. ( www. t e c h s t r e e t . c om ) .T h i s c o p y d ownl o
a d e d on2 0 1 4 - 0 1 - 0 6 0 8 : 2 8 : 2 8 - 0 6 0 0 b y a u t h or i z e d u s er P h am V an c h i .
N of ur t h er r e pr o d u c t i on or d i s t r i b u t i oni s p er mi t t e d .
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– 24 – PAS 61975 © IEC:2004 (E)
2.1.1 Measurements
General
The following measurements should only be regarded as typical since they will
vary with different control system designs.
Test Objectives
To confirm that the correct measurements are transmitted to the appropriate
points within the control equipment.
Test Procedure
All measurements shall be checked for appropriate level, polarity, phasing and
sequence at both source and destination.
- Line side voltage/test supply for valve firing;
- Valve winding currents;
- DC current and voltage;
- di/dt if applicable;
- Alpha and Gamma responses;
- Active and reactive power;
- Frequency.
2.1.2 Control and Protective Sequences
General
The sequences described in the Test Procedure can be checked with the
converter system off-load.
C o p y r i gh t e d m a t er i al l i c en s e d t oE l e c t r i c i t y of V i e t n am b y T h om s on S c i en t i f i c ,I n c
. ( www. t e c h s t r e e t . c om ) .T h i s c o p y d ownl o
a d e d on2 0 1 4 - 0 1 - 0 6 0 8 : 2 8 : 2 8 - 0 6 0 0 b y a u t h or i z e d u s er P h am V an c h i .
N of ur t h er r e pr o d u c t i on or d i s t r i b u t i oni s p er mi t t e d .
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PAS 61975 © IEC:2004 (E) – 25 –
Test Objectives
To ensure that the operational sequences of the valve control and protection are
correct.
Test Procedure
Check that the correct sequence of events, with appropriate timings take place
during deblocking/blocking of the converter system.
Check that the valve firing pulse sequences sent to the firing controls are correct
Check that forced retard, valve refire and blocking signals are generated in the
correct locations and are transmitted to the correct locations.
Formation of bypass pairs should be checked if applicable.
2.1.3 Steady State Performance Tests Test Objectives
To ensure that the basic control functions meet the designed performance. The
following tests should be regarded as typical since they may vary with different
designs of control equipment.
Test Procedure
Verify the DC voltage and current static characteristics.
C o p y r i gh t e d m a t er i al l i c en s e d t oE l e c t r i c i t y of V i e t n am b y T h om s on S c i en t i f i c ,I n c
. ( www. t e c h s t r e e t . c om ) .T h i s c o p y d ownl o
a d e d on2 0 1 4 - 0 1 - 0 6 0 8 : 2 8 : 2 8 - 0 6 0 0 b y a u t h or i z e d u s er P h am V an c h i .
N of ur t h er r e pr o d u c t i on or d i s t r i b u t i oni s p er mi t t e d .
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With the converter system deblocked check:
- Alpha and gamma order calibration;
- With the voltage and frequency of the AC systems varied over their normal
ranges of operation confirm that the current order can be varied over the full
range, DC voltage and current can be confirmed at different levels of currents
order, and that any prescribed limits are maintained;
- that the power order can be varied over the full range, the derived current
order may be confirmed at different levels of power order;
- block the rectifier and confirm the current error calibration and the correct re-
sponse of the gamma control loop.
Reduced DC Voltage Operation
Manual or automatic reduction of DC voltage may be required to reduce stresses
on DC cables when the power transfer level is being reduced, or to reduce the
possibility of flashover of overhead DC lines during extreme weather conditions
or conditions of excessive contamination.
Manual reduction will simply be cone by a selector switch operating the tap
changer control. With automatic operation check that the reduction occurs under
the designed conditions.
Protective shut-down
With minimum current order setting and the converter system deblocked apply a
protective blocking signal at the rectifier. Repeat with maximum continuous
current order setting. Confirm that correct blocking sequence occurs followed bycircuit breaker tripping if required. Repeat for protective blocking at the inverter
and with reversed power flow if appropriate.
Test Acceptance Criteria
For all the above tests the performance should conform to the system studies
and the design parameters.
C o p y r i gh t e d m a t er i al l i c en s e d t oE l e c t r i c i t y of V i e t n am b y T h om s on S c i en t i f i c ,I n c
. ( www. t e c h s t r e e t . c om ) .T h i s c o p y d ownl o
a d e d on2 0 1 4 - 0 1 - 0 6 0 8 : 2 8 : 2 8 - 0 6 0 0 b y a u t h or i z e d u s er P h am V an c h i .
N of ur t h er r e pr o d u c t i on or d i s t r i b u t i oni s p er mi t t e d .
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PAS 61975 © IEC:2004 (E) – 27 –
2.2 Dynamic Performance Tests
Introduction
For the dynamic performance tests only the closed loop controls of the HVDC
System Control (Master Control), Station Control, Pole Controls and Converter
Controls would be used. The telecommunication system shall be adequately
simulated. Protection for the DC system would also be included. Tests would be
performed using a real time HVDC Simulator. The control equipment hardware
used for the representation need not necessarily be that supplied for the
Contractor, but should be functionally identical. If the idea is to check software
and hardware problems, they should be supplied by the Contractor's equipment.
Test Objectives
1. To check that measurements for the controls are of the correct
magnitude and phasing.
2. To check that the sequences for deblocking/blocking, the firing sequencefor the valves, and the signals for forced retard, refire bypassing and
blocking are correct.
3. To check the stability and response of the controls during transient
disturbances.
4. To make preliminary settings of the control parameters.
5. To check the correct operation of the protective functions for various
types of faults in the DC system and the associated AC systems.
6. To find and correct any hardware deficiencies and software errors.
7. To check the interaction between the AC and DC systems under all
relevant operating conditions.
8. Crosscheck against digital studies for consistency.
C o p y r i gh t e d m a t er i al l i c en s e d t oE l e c t r i c i t y of V i e t n am b y T h om s on S c i en t i f i c ,I n c
. ( www. t e c h s t r e e t . c om ) .T h i s c o p y d ownl o
a d e d on2 0 1 4 - 0 1 - 0 6 0 8 : 2 8 : 2 8 - 0 6 0 0 b y a u t h or i z e d u s er P h am V an c h i .
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Preconditions for the Tests
In addition to the general preconditions the following must be fulfilled.
1. The preliminary control parameters as defined by the controls design
study have been installed.
2. The set points, thresholds and time delays of the protective relays as
defined by the protection co-ordination study have been checked by
injection tests.
3. The steady state performance defined in section 2.1 shall have been
demonstrated.
Test Procedures
The procedure for each of the following tests will be described separately in
each section.
2.2.1 Control - Step Response
2.2.2 Control Mode Transfer
2.2.3 AC System Interaction/Control
2.2.4 Commutation Failures and Valve Misfires
2.2.5 AC Filter, Transformer and Reactive Element Switching
2.2.6 AC and DC System Faults
2.2.7 Islanding
All tests for optimization and verification of the controls and protection dynamic
performance require a similar recording and monitoring set-ups as listed below,
in cases where additional or different set-ups are required these are listed in the
individual sections.
The results of these tests will be used as references for the end-to-end tests and
the operation and integration tests at site and it is desirable that similar
recording equipment and test report formats are used for both test sequences.
C o p y r i gh t e d m a t er i al l i c en s e d t oE l e c t r i c i t y of V i e t n am b y T h om s on S c i en t i f i c ,I n c
. ( www. t e c h s t r e e t . c om ) .T h i s c o p y d ownl o
a d e d on2 0 1 4 - 0 1 - 0 6 0 8 : 2 8 : 2 8 - 0 6 0 0 b y a u t h or i z e d u s er P h am V an c h i .
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Where practical the following should be monitored:
- Current or power order
- DC current
- DC voltage
- Alpha order
- Alpha response
- Gamma response
- Control mode identification
- AC busbar voltages and frequency
- Valve winding AC currents- DC power
- Reactive power
- Forced retard, blocking and initiation commands
- Valve firing sequence
- Tap position indications (if available)
2.2.1 Controls-Step Responses General
The corresponding site tests are described in 6.2.1 of the operation and
integration tests.
Test Objectives
To confirm that the control equipment operates in a stable manner during
changes of current order, power order and converter control angle.
Test Procedure
The AC systems should be set up with the strongest rectifier system together
with the weakest inverter system applicable, since these typically represent the
most onerous operating conditions. However, other cases should be considered.
C o p y r i gh t e d m a t er i al l i c en s e d t oE l e c t r i c i t y of V i e t n am b y T h om s on S c i en t i f i c ,I n c
. ( www. t e c h s t r e e t . c om ) .T h i s c o p y d ownl o
a d e d on2 0 1 4 - 0 1 - 0 6 0 8 : 2 8 : 2 8 - 0 6 0 0 b y a u t h or i z e d u s er P h am V an c h i .
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– 30 – PAS 61975 © IEC:2004 (E)
With current order setting of 0,1 pu, deblock and block the converter system.
Confirm that the speed of response to achieve the ordered value conforms to the
specification and that no significant overshoot occurs. The procedure should be
repeated for both power flow directions, if appropriate.
If a prescribed ramping rate for current order is required apply a step change of
0,5 pu or 1,0 pu current order to confirm that the correct rates are achieved.
Current order step response
With the converter system in DC current control and current order settings of
0,15 pu, 0,5 pu or 1,0 pu apply a 0,05 pu step reduction in current order followedby a 0,05 pu step up. Sufficient time should be allowed between changes to
allow stable operation to be achieved.
Inverter extinction angle step response
With the rectifier in its normal mode of control and the inverter in minimum
constant extinction angle control, apply a step change in gamma to increase the
reference. An equal step reduction in gamma to the original value should beapplied.
Inverter current control step responses
With the rectifier in constant firing angle control (alpha minimum) and the
inverter in constant current control mode apply a 0,05 pu step increase in current
order, followed by a corresponding reduction after a suitable time period.
Power order step responses
With the converter system in power control and the order set at 0,15 pu, 0,5 pu
or 1,0 pu apply a step down in order of 0,05 pu followed by a corresponding
increase after a suitable period.
NOTE Other control loops, for example, constant DC voltage, may be tested similarly to
the above, the general principle being that step changes shall be small enough that
converter firing angles do not reach limits.
C o p y r i gh t e d m a t er i al l i c en s e d t oE l e c t r i c i t y of V i e t n am b y T h om s on S c i en t i f i c ,I n c
. ( www. t e c h s t r e e t . c om ) .T h i s c o p y d ownl o
a d e d on2 0 1 4 - 0 1 - 0 6 0 8 : 2 8 : 2 8 - 0 6 0 0 b y a u t h or i z e d u s er P h am V an c h i .
N of ur t h er r e pr o d u c t i on or d i s t r i b u t i oni s p er mi t t e d .
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PAS 61975 © IEC:2004 (E) – 31 –
Test Acceptance Criteria
All controller settings should be adjusted such that the response and recovery
times as specified or as defined by system studies are achieved.
No instability should be apparent in the step response tests and the responses
shall be well damped without significant overshoot.
2.2.2 Control Mode Transfer
General
The most common transfers between control modes are:
- at the rectifier, from constant power control mode to constant current order
mode and back;
- at the inverter, from constant extinction angle control mode to constant
current control mode and back;
- at the rectifier, from normal alpha control mode to minimum alpha mode.
Additional control modes may be used:
- at the inverter, constant DC voltage control may be used for weak AC
system applications;
- for both rectifier and inverter, control of AC system voltage may be used
during temporary load rejection conditions.
The corresponding site tests are described in 6.2.2 of the operation and
integration tests.
C o p y r i gh t e d m a t er i al l i c en s e d t oE l e c t r i c i t y of V i e t n am b y T h om s on S c i en t i f i c ,I n c
. ( www. t e c h s t r e e t . c om ) .T h i s c o p y d ownl o
a d e d on2 0 1 4 - 0 1 - 0 6 0 8 : 2 8 : 2 8 - 0 6 0 0 b y a u t h or i z e d u s er P h am V an c h i .
N of ur t h er r e pr o d u c t i on or d i s t r i b u t i oni s p er mi t t e d .
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Test Objectives
Control mode transfer tests are performed to verify that the change from one
control mode to another can be achieved without adverse interaction.
Test Procedure
The transfer from constant power control to constant current control and back
can be done manually. The change from inverter constant extinction angle
control to constant current control may be activated automatically by reducing
the rectifier AC system voltage thus forcing the rectifier to minimum alphaoperation. To demonstrate return to the inverter constant extinction angle control
mode the rectifier AC system voltage should be increased. Similarly a change
from inverter constant DC voltage control to constant current control can be
activated automatically.
To activate the AC system voltage control either the "remote" converter should
be temporarily blocked, or a three phase solid short-circuit should be applied to
its AC busbars.
Test Acceptance Criteria
Control mode transfers should occur without inducing adverse interaction.
Step changes in power shall not occur during transfer from constant power
control to constant current control.
Transfer from constant extinction angle control or constant DC voltage control to
constant current control at the inverter must be stable.
Activation of the AC system voltage control should occur during temporary DC
system shutdown.
C o p y r i gh t e d m a t er i al l i c en s e d t oE l e c t r i c i t y of V i e t n am b y T h om s on S c i en t i f i c ,I n c
. ( www. t e c h s t r e e t . c om ) .T h i s c o p y d ownl o
a d e d on2 0 1 4 - 0 1 - 0 6 0 8 : 2 8 : 2 8 - 0 6 0 0 b y a u t h or i z e d u s er P h am V an c h i .
N of ur t h er r e pr o d u c t i on or d i s t r i b u t i oni s p er mi t t e d .
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PAS 61975 © IEC:2004 (E) – 33 –
2.2.3 AC System Interaction/Control
General
The flexibility of the controls of HVDC systems enables them to be used to
enhance the performance of the associated AC systems. Examples of such
features are:
- control of AC system frequency;
- modulation of transmitted power to assist in fault recovery;
- limitation of overvoltage during load rejection on the DC system;
- limitation of reactive power demand from the AC systems during load changes;
- AC system voltage control.
The corresponding site tests are described in 6.2.3 of the operation and
integration tests.
Test Objectives
To check the performance of specific control functions which may berequirements of the Contract Specification.
Test Procedure
Power/Current Control Modulation
For AC system damping acquire an appropriate level of signal and frequency
and inject this into the modulation control loop and confirm that the response
varies in compliance with system studies. Inject an appropriate level of signalinto the frequency control loop and confirm that the response varies in
compliance with the specified requirements. Alternatively a frequency change
may be induced by tripping a generator.
Limitations of AC System Overvoltage
With the maximum rating of reactive power elements connected, and at the
maximum power transfer level block the inverter for a defined duration and check
that the dynamic voltage is limited to the design level. Repeat by blocking the
rectifier under the same operating conditions.
C o p y r i gh t e d m a t er i al l i c en s e d t oE l e c t r i c i t y of V i e t n am b y T h om s on S c i en t i f i c ,I n c
. ( www. t e c h s t r e e t . c om ) .T h i s c o p y d ownl o
a d e d on2 0 1 4 - 0 1 - 0 6 0 8 : 2 8 : 2 8 - 0 6 0 0 b y a u t h or i z e d u s er P h am V an c h i .
N of ur t h er r e pr o d u c t i on or d i s t r i b u t i oni s p er mi t t e d .
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Control of Reactive Power Exchange with the AC Systems
Confirm that the reactive power elements are switched in or out, at the
prescribed power transmission levels, as the power order is increased to its
maximum value and then reduced to its minimum value. Check that the control
angles at the rectifier and inverter remain within the defined bands during the
power changes.
Test Acceptance Criteria
For all the above tests the performance should conform with the system studies
and the design parameters.
No adverse interactions should occur
2.2.4 Commutation Failures and Valve Misfires
General
Because of the interaction of the DC system with both of the AC systems towhich it is connected, various forms of valve faults should be applied to
demonstrate either the adequacy of the recovery performance of the DC system
after fault clearance, or that the correct protective actions leading to shutdown of
part or all of the DC system are correctly performed.
The corresponding site tests are described in 6.2.4 of the operations and inte-
gration tests.
Test Objectives
To simulate commutation failure of a converter valve, the recovery procedure
and performance.
To simulate misfiring of a converter valve and the operation of any specialized
protection if this is applied.
C o p y r i gh t e d m a t er i al l i c en s e d t oE l e c t r i c i t y of V i e t n am b y T h om s on S c i en t i f i c ,I n c
. ( www. t e c h s t r e e t . c om ) .T h i s c o p y d ownl o
a d e d on2 0 1 4 - 0 1 - 0 6 0 8 : 2 8 : 2 8 - 0 6 0 0 b y a u t h or i z e d u s er P h am V an c h i .
N of ur t h er r e pr o d u c t i on or d i s t r i b u t i oni s p er mi t t e d .
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PAS 61975 © IEC:2004 (E) – 35 –
Test Procedure
Some extra monitoring may be applied:
- timing signals allowing synchronization between recordings;- one valve voltage on each converter group;
- crucial protection signals.
Commutation Failure
Valve commutation failure (which is most likely to occur at an inverter) can be
simulated by blocking the start pulse at one valve. The duration of blocking the
start pulse should be such that a single commutation failure occurs, then for a
duration sufficient to activate valve overload protection (i.e. voltage dependent
current limit), and finally for a duration sufficient to activate the persistent
commutation failure protection.
Valve Misfire
Valve misfire at a rectifier can be simulated by blocking the start pulse to one
valve. The duration should be sufficient to ensure that specialized protection,
e.g. asymmetry protection or excessive harmonic protection, will operate.
Test Acceptance Criteria
The acceptance criteria are:
- for valve commutation failures the corrective action by the control or
protective systems should be initiated and be successful over the entire
range of power transfer. Operation of the line fault detection should not
occur.
- for valve misfire the correct protective shutdown should occur.
C o p y r i gh t e d m a t er i al l i c en s e d t oE l e c t r i c i t y of V i e t n am b y T h om s on S c i en t i f i c ,I n c
. ( www. t e c h s t r e e t . c om ) .T h i s c o p y d ownl o
a d e d on2 0 1 4 - 0 1 - 0 6 0 8 : 2 8 : 2 8 - 0 6 0 0 b y a u t h or i z e d u s er P h am V an c h i .
N of ur t h er r e pr o d u c t i on or d i s t r i b u t i oni s p er mi t t e d .
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– 36 – PAS 61975 © IEC:2004 (E)
2.2.5 AC Filter, Transformer and Reactive Element Switching
General
The corresponding site tests are described in 6.3 of the operation and integration
tests.
Test Objectives
To confirm that switching of such elements will not have any adverse effect on
the operation of the DC system, that AC system voltage disturbances are within
the prescribed limits and that if resonances occur they are adequately damped.
Proper recovery from commutation failure, if any, should be verified.
Test Procedure
The short circuit ratios of the AC systems should be at the specified minimum
values or for resonant investigations at an appropriate value.
Additional recordings may be made of transformer primary current, and AC filter,
shunt capacitor and shunt reactor currents during the appropriate parts of thetest sequence.
If the system is bipolar then the transformer switching tests can be carried out in
monopolar configuration using one of the transformers from the second pole. For
a monopolar scheme a representation of a relevant system transformer of
suitable rating should be used.
!f the scheme has two or more converter groups per pole then switching of onetransformer with the remaining groups in service is possible provided the
scheme filters are designed for this mode of operation.
Switching on and off each type of filter should be done in turn with the converter
equipment energized.
If capacitor banks or shunt reactors form part of the overall scheme then
switching of these elements singly or in appropriate combinations should bedone with the converters energized.
C o p y r i gh t e d m a t er i al l i c en s e d t oE l e c t r i c i t y of V i e t n am b y T h om s on S c i en t i f i c ,I n c
. ( www. t e c h s t r e e t . c om ) .T h i s c o p y d ownl o
a d e d on2 0 1 4 - 0 1 - 0 6 0 8 : 2 8 : 2 8 - 0 6 0 0 b y a u t h or i z e d u s er P h am V an c h i .
N of ur t h er r e pr o d u c t i on or d i s t r i b u t i oni s p er mi t t e d .
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PAS 61975 © IEC:2004 (E) – 37 –
The switching tests should be repeated for both rectifier and inverter terminals
and with reversed power flow, if appropriate.
Test Acceptance Criteria
In all switching tests the HVDC system should continue in stable operation. The
AC system voltage disturbances should be within the specified limits.
During a switching operation commutation failure may occur but should be
limited to only one event
2.2.6 AC and DC System Faults
General
Because of the interaction of the DC system with both of the AC systems to
which it is connected, various forms of AC and DC faults should be applied to
demonstrate either the adequacy of the recovery performance of the DC system
after fault clearance, or that the correct protective actions leading to shutdown of
part of all of the DC system are correctly performed.
Local AC system faults, which give 100 % voltage reduction in one phase, or all
3 phases, and remote AC system faults which give, say, 30 % voltage reduction
in one phase, or all 3 phases, should be applied, each being applied for the
specified fault duration.
Due to current inrush conditions during recovery period the voltages may be
severely distorted, but this should not affect the correct performance of the
control and protection systems.
During some AC system faults commutation failure of the converter system is
inevitable, but this condition must be of limited duration and must not adversely
affect the recovery performance of the complete system.
C o p y r i gh t e d m a t er i al l i c en s e d t oE l e c t r i c i t y of V i e t n am b y T h om s on S c i en t i f i c ,I n c
. ( www. t e c h s t r e e t . c om ) .T h i s c o p y d ownl o
a d e d on2 0 1 4 - 0 1 - 0 6 0 8 : 2 8 : 2 8 - 0 6 0 0 b y a u t h or i z e d u s er P h am V an c h i .
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For DC line faults the normal clearance procedure is to suppress the DC voltage
by means of converter control action, with a preset time to allow deionization at
the fault and then reapply the DC voltage.
If the fault is not cleared, a preset number of such sequences can be repeated
including (if applicable) a restart at reduced voltage before permanent shutdown
is applied. For DC cable faults it is assumed that such faults are permanent and
shutdown of the affected cable is immediate.
The corresponding site tests are described in 6-5 of the operation and integra-
tion tests.
Test Objectives
To apply single-phase and three-phase faults to either AC system, in locations
close to or distant from the converter terminals, in order to demonstrate the
performance of the converter system during the faults and the recovery
performance subsequent to the faults.
To apply DC line (or cable) faults at different locations to demonstrate theprotective actions taken by the converter controls are correct.
To apply simulated faults at different points within the DC terminals and
demonstrate correct protective action and shutdown.
To verify that the correct protection co-ordination was achieved.
To check that the pole loss compensation system (if applicable) operates
correctly.
Test Procedure
Some extra monitoring may be applied:
- timing signals allowing synchronization between recordings;
- one valve voltage on each converter group;
- crucial protection signals.
C o p y r i gh t e d m a t er i al l i c en s e d t oE l e c t r i c i t y of V i e t n am b y T h om s on S c i en t i f i c ,I n c
. ( www. t e c h s t r e e t . c om ) .T h i s c o p y d ownl o
a d e d on2 0 1 4 - 0 1 - 0 6 0 8 : 2 8 : 2 8 - 0 6 0 0 b y a u t h or i z e d u s er P h am V an c h i .
N of ur t h er r e pr o d u c t i on or d i s t r i b u t i oni s p er mi t t e d .
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PAS 61975 © IEC:2004 (E) – 39 –
AC System Faults
The sequence of faults should be as follows.
- 1-phase busbar fault at the rectifier, repeated at 0,1 pu and 1,0 pu load;
- remote 1-phase fault at the rectifier, repeated at 0,1 pu and 1,0 pu load;
- local 3-phase fault at the rectifier, repeated at 0,1 pu and 1,0 pu load;
- distant 3-phase fault at the rectifier, repeated at 0,1 pu and 1,0 pu load;
- repeat of the above 1- and 3-phase faults applied at the inverter AC system;
- repeat of the above 1- and 3-phase faults at specified locations within either
of the AC systems if there are locations of special interest;
- repeat all of the above tests if the system has reversed power flow;
- repeat some of the tests with a different fault duration and with the specified
power overload.
DC System Faults
The sequence of faults should be as follows.
- temporary fault application to the DC line at a point adjacent to the rectifier
terminal, at the mid-point of the line and at a point adjacent to the inverter
terminal. For cable connections permanent faults should be applied at these
three locations;
- apply permanent faults to demonstrate bushing flashovers of say DC reactor,
HVDC wall bushing or transformer valve winding bushing of the star and
delta windings;
- apply a short circuit between phases on the valve side of the converter trans-
former,
- verify that back-up protection operates correctly if the primary protection isdisabled.
C o p y r i gh t e d m a t er i al l i c en s e d t oE l e c t r i c i t y of V i e t n am b y T h om s on S c i en t i f i c ,I n c
. ( www. t e c h s t r e e t . c om ) .T h i s c o p y d ownl o
a d e d on2 0 1 4 - 0 1 - 0 6 0 8 : 2 8 : 2 8 - 0 6 0 0 b y a u t h or i z e d u s er P h am V an c h i .
N of ur t h er r e pr o d u c t i on or d i s t r i b u t i oni s p er mi t t e d .
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Test Acceptance Criteria
AC System Faults
The acceptance criteria are:
- the DC system shall remain stable during and after clearing of the fault;
- the time for DC power recovery shall within the specified limits;
- no spurious operation of protection relays should occur;
- transient AC and DC voltages should be contained within the specified
levels;
- permanent faults should result in correct shutdown of the remote station
without the use of telecommunication signals;
- inverter AC system faults should not cause inadvertent operation of the DC
line protection.
DC System Faults
The acceptance criteria are:
- For DC line faults the correct fault clearance sequence should occur and
operation of protection on the converter side of the DC line reactors or the
line protection in the unfaulted pole should not occur.
- For DC cable faults safe protective shutdown should occur.
- For bushing flashovers within the converter terminals the correct protective
shutdown should occur at both stations with and without telecommunication.
- For transformer valve winding faults the correct protective shutdown should
occur.
- The pole loss compensation scheme operates correctly.
C o p y r i gh t e d m a t er i al l i c en s e d t oE l e c t r i c i t y of V i e t n am b y T h om s on S c i en t i f i c ,I n c
. ( www. t e c h s t r e e t . c om ) .T h i s c o p y d ownl o
a d e d on2 0 1 4 - 0 1 - 0 6 0 8 : 2 8 : 2 8 - 0 6 0 0 b y a u t h or i z e d u s er P h am V an c h i .
N of ur t h er r e pr o d u c t i on or d i s t r i b u t i oni s p er mi t t e d .
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PAS 61975 © IEC:2004 (E) – 41 –
2.2.7 Islanding
General
The term Islanding can cover several operating conditions associated with
HVDC systems. Two examples of islanding are:
- isolation of the inverter terminal of the HVDC system due to switching out of
a single AC transmission line which connects the HVDC system to the main
AC system;
- loss of the main AC system leaving one or more rotating machines
connected to either terminal of the HVDC system.
In the first example power transmission would continue in the HVDC until the
problem was identified and corrected and would result in severe overvoltage on
the AC filters, other components used for reactive compensation, the converter
transformers and valves at the inverter terminal, if no protective action was
taken.
In the second example, loss of the main system would result in the remaining
machines being unsynchronized. Depending on whether the main system had
been supplying power to or absorbing power from the HVDC system the
remaining machines could quickly reduce or increase speed unless the HVDC
system had suitable controls to prevent such changes in frequency.
Test Objectives
To demonstrate the effective action of the protection or control action of the
HVDC system when some form of Islanding occurs.
C o p y r i gh t e d m a t er i al l i c en s e d t oE l e c t r i c i t y of V i e t n am b y T h om s on S c i en t i f i c ,I n c
. ( www. t e c h s t r e e t . c om ) .T h i s c o p y d ownl o
a d e d on2 0 1 4 - 0 1 - 0 6 0 8 : 2 8 : 2 8 - 0 6 0 0 b y a u t h or i z e d u s er P h am V an c h i .
N of ur t h er r e pr o d u c t i on or d i s t r i b u t i oni s p er mi t t e d .
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– 42 – PAS 61975 © IEC:2004 (E)
Test Procedure
In the first example given above, the HVDC system should be run at minimum
power transfer with the AC system at minimum short circuit capacity and the ACcircuit breaker at the remote end of the single AC transmission line, which is
connected to the inverter terminal, should be opened.
The action of the HVDC system will depend on whether or not auto-reclose of
the AC circuit breaker is applicable. If auto-reclose of the breaker is applicable,
the protection of the HVDC system should detect that the breaker has opened
and initiate action in the HVDC system controls to avoid any excessive
overvoltage. The HVDC system should then be held in readiness for power
restoration following reclosure of the breaker, if auto-reclose is not applicable
then the HVDC system protection should initiate action in the HVDC system
controls to avoid excessive overvoltage and then safely shut down the HVDC
system. The test should be repeated at other levels of power transfer.
In the second example the HVDC system should be run at a power level
consistent with the rating of the connected AC machines, at the appropriate
converter terminal, plus low power being supplied by the connected main AC
system. The breaker connecting the main AC system should be opened. The
HVDC system controls should operate to regulate the frequency of the machines
to the prescribed value. The test should be repeated with higher levels of power
being supplied by the main AC system and then with power being absorbed by
the main AC system.
Test Acceptance Criteria
Depending upon the type of islanding applicable to the HVDC system, protection
and/or control action shall be taken by the HVDC system to ensure, if it is
appropriate to the application, that overcurrent or overvoltage damage, or
significant frequency deviation of the connected AC machines do not occur.
C o p y r i gh t e d m a t er i al l i c en s e d t oE l e c t r i c i t y of V i e t n am b y T h om s on S c i en t i f i c ,I n c
. ( www. t e c h s t r e e t . c om ) .T h i s c o p y d ownl o
a d e d on2 0 1 4 - 0 1 - 0 6 0 8 : 2 8 : 2 8 - 0 6 0 0 b y a u t h or i z e d u s er P h am V an c h i .
N of ur t h er r e pr o d u c t i on or d i s t r i b u t i oni s p er mi t t e d .
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PAS 61975 © IEC:2004 (E) – 43 –
2.3 Functional Performance Test Introduction
As discussed in the general introduction for the functional performance test the
complete control system including telecommunication interface will be testedagainst some form of simulation of the HVDC system including the DC
switchgear and the AC switchgear. The appropriate telecommunication time
delays shall be simulated.
General
The control system hardware and software shall be the actual and completedeliverables.
The simulation can be by a real time simulator, software modules or a
combination of both.
Test Objectives
1. To check that all individual control cubicles function properly.
2. To check that all control cubicles interact properly.
3. To check that all interfaces between the control cubicles and all other
equipment are correct.
4. To check that all transfers to redundant controls are smooth and do not
affect the operation of the on-line equipment.
5. To verify that power supplies with redundant elements do not affect
controls or protection operation in case one element is shut down.
6. To verify that failed elements can be removed and replaced without
affecting the operation of the on-line equipment.
C o p y r i gh t e d m a t er i al l i c en s e d t oE l e c t r i c i t y of V i e t n am b y T h om s on S c i en t i f i c ,I n c
. ( www. t e c h s t r e e t . c om ) .T h i s c o p y d ownl o
a d e d on2 0 1 4 - 0 1 - 0 6 0 8 : 2 8 : 2 8 - 0 6 0 0 b y a u t h or i z e d u s er P h am V an c h i .
N of ur t h er r e pr o d u c t i on or d i s t r i b u t i oni s p er mi t t e d .
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– 44 – PAS 61975 © IEC:2004 (E)
7. Where redundancy is applied it shall be verified that:
- single contingency failures do not cause a shutdown;
- failure of one element of a redundant system initiates changeover to
the standby element;
- failure of all redundant elements should result in safe shutdown.
Preconditions
1, The simulator must represent the defined HVDC system, the DCswitchgear and the AC switchgear and be operational.
2. The control equipment to be tested must have passed the factory routine
test and must be available for operation at the test site.
3. The test arrangement shall be defined and agreed upon between the
user and the manufacturer.
4, A test plan shall be mutually agreed upon between the user and the
manufacturer before commencement of tests.
5. Metering and recording equipment shall be available and connected to
the test.
6, The deliverables for the control system including cubicle interconnections
shall be installed and connected to the simulator.
7. The steady state performance defined in 2.1 shall have been demonstrated.
Test Procedure
Each cubicle and the operators interface shall first be commissioned separately
and then be connected with each other.
C o p y r i gh t e d m a t er i al l i c en s e d t oE l e c t r i c i t y of V i e t n am b y T h om s on S c i en t i f i c ,I n c
. ( www. t e c h s t r e e t . c om ) .T h i s c o p y d ownl o
a d e d on2 0 1 4 - 0 1 - 0 6 0 8 : 2 8 : 2 8 - 0 6 0 0 b y a u t h or i z e d u s er P h am V an c h i .
N of ur t h er r e pr o d u c t i on or d i s t r i b u t i oni s p er mi t t e d .
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PAS 61975 © IEC:2004 (E) – 45 –
The function listed below should be tested for normal operating conditions. It will
also be necessary to test some of these functions in contingency operation
conditions. Normal operation applies to undisturbed operation of the HVDC
System. Contingency operation exists if a single failure occurs fn the HVDC-
System but the System can continue operation within specified limits or a
disturbance occurs in either AC-System which requires a specified action in the
HVDC System.
In order to create contingency operating conditions malfunctions shall be
deliberately simulated at the simulator. Typical functions are:
- change of HVDC system configuration;- change status of operation;
- change energy transfer level and energy direction;
- change preselections;
- steady state converter control;
- switching of reactive power compensation elements;
- loss of redundancy and power supplies for the Controls and Protection;
- apply various invalid inputs to the control system and check that invalid
signals are alarmed to the operator;
- runback functions;
- power modulation;
- loss of end-to-end telecommunication;
- change of control location.
Test Acceptance Criteria
- all functions of the control system must work properly. Initiated signals must
follow the designated signal path, generate the appropriate command and
create the checkback signal to indicate the execution of the correct action on
the operators interface.
C o p y r i gh t e d m a t er i al l i c en s e d t oE l e c t r i c i t y of V i e t n am b y T h om s on S c i en t i f i c ,I n c
. ( www. t e c h s t r e e t . c om ) .T h i s c o p y d ownl o
a d e d on2 0 1 4 - 0 1 - 0 6 0 8 : 2 8 : 2 8 - 0 6 0 0 b y a u t h or i z e d u s er P h am V an c h i .
N of ur t h er r e pr o d u c t i on or d i s t r i b u t i oni s p er mi t t e d .
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– 46 – PAS 61975 © IEC:2004 (E)
- loss of a redundant element for control or protection should not affect the DC
system operation.
- loss of a redundant element of the power supplies should not affect the DC
system operation;- for loss of both elements of a power supply system with redundancy the DC
system should shut down safely;
- normal transitions between redundant elements for control or protection
should not disturb the AC systems. Non-allowable combinations should
either be impossible or result in safe shutdown of the DC system;
- failure of a single input measurement, where measurements are redundant,
should not result in disturbance to the AC or DC systems;
- failure of an unduplicated measurement, or both duplicated measurements,
should result in safe shutdown of the DC system.
2.4 Type Tests on the Control and Protection Equipments
Introduction
Some of the type tests, if specifically required for the contract, may be carried
out on the control and protection equipment, together with communication
interfaces. These tests would demonstrate the equipment performance over the
specified environmental conditions together with specified variation of the
auxiliary supply voltage. In addition the immunity of each equipment to
electromagnetic and electrostatic disturbances may be demonstrated.
Since these tests are carried out with the control and protection equipment in an
operational state it may be convenient to carry out these type tests white the
equipment is connected to the HVDC simulator, though alternative methods
would be equally acceptable.
C o p y r i gh t e d m a t er i al l i c en s e d t oE l e c t r i c i t y of V i e t n am b y T h om s on S c i en t i f i c ,I n c
. ( www. t e c h s t r e e t . c om ) .T h i s c o p y d ownl o
a d e d on2 0 1 4 - 0 1 - 0 6 0 8 : 2 8 : 2 8 - 0 6 0 0 b y a u t h or i z e d u s er P h am V an c h i .
N of ur t h er r e pr o d u c t i on or d i s t r i b u t i oni s p er mi t t e d .
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PAS 61975 © IEC:2004 (E) – 47 –
Test Objective
To demonstrate that the control performance is not affected by operation at
various environmental conditions and within the prescribed operating range ofthe power supply.
To demonstrate that the protection settings and timings are not affected by
operation at temperatures and within the prescribed operating range of the
power supply.
To demonstrate that the specified levels of electromagnetic and electrostatic
disturbances do not cause misoperation of control and protection equipments-
To demonstrate that hand held communication equipment does not cause
misoperation of control and protection equipment.
Test Procedure
The following procedure covers type testing with respect to Control Cubicles:
- temperature;
- power supply variations;
- electromagnetic and electrostatic disturbance;
- hand held communication equipment.
Enclose the cubicle to be tested within a thermally insulated housing with a heat
source.
Operate the HVDC system at 1,0 pu load.
With the cubicle temperature initially at room ambient:
- Check that the DC voltage and current measurements are stable during all
control modes;
- Check the accuracy of all the control loops by comparing their respective
settings with their responses;
- Check the transient response by applying step changes in current order.- Vary the voltage (and frequency if appropriate) of the power supply to the
C o p y r i gh t e d m a t er i al l i c en s e d t oE l e c t r i c i t y of V i e t n am b y T h om s on S c i en t i f i c ,I n c
. ( www. t e c h s t r e e t . c om ) .T h i s c o p y d ownl o
a d e d on2 0 1 4 - 0 1 - 0 6 0 8 : 2 8 : 2 8 - 0 6 0 0 b y a u t h or i z e d u s er P h am V an c h i .
N of ur t h er r e pr o d u c t i on or d i s t r i b u t i oni s p er mi t t e d .
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– 48 – PAS 61975 © IEC:2004 (E)
control equipment, to the specified maximum and minimum levels and at
each voltage level recheck the steady state and transient performance and
compare results;
- Raise the temperature within the housing to the highest specified ambienttemperature, preferably for several hours;
- Recheck the steady state accuracy and transient performance and compare
results;
- Vary the voltage (and frequency if appropriate) of the power supply to the
control equipment to the specified maximum and minimum levels and at each
voltage level recheck the steady state accuracy and transient performance
and compare results;- Reduce the temperature within the housing to nominal ambient;
- Recheck the steady state and transient performance and compare results.
With the DC system operating at 1,0 pu load, subject the control equipment to
the appropriate electromagnetic and electrostatic interference, and demonstrate
that there is no disturbance to the operation of the DC system.
Protection Cubicles
Enclose the protection cubicle to be tested within a thermally insulated housing
with a heat source.
With the cubicle temperature at room ambient:
- Check in turn each protection operation for setting and timing;
- Vary the voltage (and frequency if appropriate) of the power supply to the
protection cubicle to the specified maximum and minimum levels and at eachvoltage level recheck in turn each protection operation for setting and
timing;.
- Raise the temperature within the housing to the highest specified ambient
temperature, preferably for several hours.
- Recheck in turn each protection operation for setting and timing.
- Vary the voltage (and frequency if appropriate) of the power supply to the
protection cubicle to the specified maximum and minimum levels and at each
voltage level recheck in turn each protection operation for setting and timing;
C o p y r i gh t e d m a t er i al l i c en s e d t oE l e c t r i c i t y of V i e t n am b y T h om s on S c i en t i f i c ,I n c
. ( www. t e c h s t r e e t . c om ) .T h i s c o p y d ownl o
a d e d on2 0 1 4 - 0 1 - 0 6 0 8 : 2 8 : 2 8 - 0 6 0 0 b y a u t h or i z e d u s er P h am V an c h i .
N of ur t h er r e pr o d u c t i on or d i s t r i b u t i oni s p er mi t t e d .
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PAS 61975 © IEC:2004 (E) – 49 –
- Compare the results with the previous study;
- Lower the temperature to normal ambient and recheck in turn each
protection operation for setting and timing.
With the DC system operating at 1,0 pu load, subject the protection equipment to
the appropriate electromagnetic and electrostatic interference and demonstrate
that misoperation of the protection does not occur.
Test Acceptance Criteria
The steady state accuracy and transient performance results for all the tests
shall be within the design tolerances.
The setting and timing results for each protection shall be within the design
tolerances.
C o p y r i gh t e d m a t er i al l i c en s e d t oE l e c t r i c i t y of V i e t n am b y T h om s on S c i en t i f i c ,I n c
. ( www. t e c h s t r e e t . c om ) .T h i s c o p y d ownl o
a d e d on2 0 1 4 - 0 1 - 0 6 0 8 : 2 8 : 2 8 - 0 6 0 0 b y a u t h or i z e d u s er P h am V an c h i .
N of ur t h er r e pr o d u c t i on or d i s t r i b u t i oni s p er mi t t e d .
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– 50 – PAS 61975 © IEC:2004 (E)
PART 3: CONVERTER TESTS
General
Introduction
This part describes the testing of each converter station as a unit and the
verification of the HVDC transmission line prior to transmitting power. This group
of tests precedes the end-to-end testing. The following tests are outlined:
3.1 Converter unit tests
• HV energization of converter transformer
3.2 Converter station tests
• HV energization of AC-filters and shunt banks
• Open line test (HV energization) of the DC switchyard
• Load tests: Back-to-Back testing
Short circuit testing (optional)
3.3 Open line test of the DC transmission circuit
C o p y r i gh t e d m a t er i al l i c en s e d t oE l e c t r i c i t y of V i e t n am b y T h om s on S c i en t i f i c ,I n c
. ( www. t e c h s t r e e t . c om ) .T h i s c o p y d ownl o
a d e d on2 0 1 4 - 0 1 - 0 6 0 8 : 2 8 : 2 8 - 0 6 0 0 b y a u t h or i z e d u s er P h am V an c h i .
N of ur t h er r e pr o d u c t i on or d i s t r i b u t i oni s p er mi t t e d .
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PAS 61975 © IEC:2004 (E) – 51 –
During the test program, conformance with environmental specifications should
be included where applicable. Preliminary observations of audible noise, radio
and PLC interference levels may be done. This is described in Part 5 of the
guide. Temperature rise of major equipment can be monitored. However, the
actual measurement of the above mentioned quantities are conducted during
end-to-end operation.
Test of Back-to-Back stations is covered in part 4 of this guide whereas back-to-
back testing referred to in section 3.2 is accomplished by a temporary
connection between the converters of a bipolar long distance HVDC station.
Statement of Purpose
The purpose of the Converter Tests is to verify the correct operation of an
individual converter station and the proper insulation of all main circuit
equipment before starting the end-to-end testing.
General Test Objectives
The converter tests may be divided into high voltage energization and load tests.The test objective of the HV energization is to verify that proper voltage
insulation is achieved in the AC and DC main circuit equipment.
Load tests (back-to-back or short circuit tests) may be conducted to get a
provisional verification of the control system, the valve cooling capability and the
main circuit with respect to temperature rise, audible noise and radio
interference. Final verification will be made during end-to-end testing.
General Preconditions
Before beginning the Converter tests, the following equipment must be verified
off voltage and be available:
C o p y r i gh t e d m a t er i al l i c en s e d t oE l e c t r i c i t y of V i e t n am b y T h om s on S c i en t i f i c ,I n c
. ( www. t e c h s t r e e t . c om ) .T h i s c o p y d ownl o
a d e d on2 0 1 4 - 0 1 - 0 6 0 8 : 2 8 : 2 8 - 0 6 0 0 b y a u t h or i z e d u s er P h am V an c h i .
N of ur t h er r e pr o d u c t i on or d i s t r i b u t i oni s p er mi t t e d .
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– 52 – PAS 61975 © IEC:2004 (E)
- AC switchgear;
- AC filters, capacitor banks and shunt reactors;
- DC filters and switchgear;
- Converter transformers;
- Thyristor valves and cooling system;
- Station auxiliary service;
- Fire protection system;
- AC and DC protection systems;
- Control system;
- DC line or cable (for open line test);- Sequency of event ;
- Recorder and Alarm System;
- Transient Fault Recorders.
In order to verify the converter firing control, the valve base electronics and the
valve main circuit connections, prior to HV energization, it is recommended to
conduct a low voltage energization test The test may be performed by applying
0.5 - 10 kV to the primary side or to the valve side of the converter transformers
with all but a few thyristors short-circuited in each valve position. An appropriate
resistor may serve as a load on the DC-side.
Prior to the converter tests detailed procedures and plans should be prepared.
As the tests may involve some disturbance or increased risk to the connected
AC systems, the operators of the systems should be consulted.
3.1 Converter Unit Tests Introduction
This test is the HV energization of the converter transformer with blocked valves
and is performed on each individual converter unit in a HVDC station.
Test Objectives
The test objective is to verify that insulation voltage withstand is achieved and to
check that the electrical phasing is correct.
Preconditions
C o p y r i gh t e d m a t er i al l i c en s e d t oE l e c t r i c i t y of V i e t n am b y T h om s on S c i en t i f i c ,I n c
. ( www. t e c h s t r e e t . c om ) .T h i s c o p y d ownl o
a d e d on2 0 1 4 - 0 1 - 0 6 0 8 : 2 8 : 2 8 - 0 6 0 0 b y a u t h or i z e d u s er P h am V an c h i .
N of ur t h er r e pr o d u c t i on or d i s t r i b u t i oni s p er mi t t e d .
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PAS 61975 © IEC:2004 (E) – 53 –
Before conducting the HV energization the following preconditions shall be
fulfilled.
- All controls and protections associated with the high voltage equipment shall
be verified and in service. A trip test shall be made shortly before highvoltage energization.
- Monitoring instrumentation shall be connected and ready.
- All clamp joints shall have been tightened and the insulators wiped clean.
- The HVDC transmission line disconnect switch shall be opened and locked.
- All safety procedures shall have been carried out.
- A final visual inspection of the high voltage equipment shall be performed
and the arrester counter numbers shall be recorded.
- The low voltage side of the valves shall be grounded.
Test Procedures
During the test, AC voltage, steady-state and inrush-currents may be recorded.
Inspect the equipment during the test for abnormal sounds and corona
discharge. The following test sequence is recommended:
- Energize the converter transformer with the valves blocked and check the
electrical phasing through the control system.
- The converter transformer tap changers should initially be at highest position
(lowest valve side voltage) and then stepped to rated voltage.
- Keep the transformer energized for a minimum of 24 hours.
Test Acceptance Criteria
No abnormal sounds or corona discharge shall occur in the energized
equipment. No protections shall operate improperly.
C o p y r i gh t e d m a t er i al l i c en s e d t oE l e c t r i c i t y of V i e t n am b y T h om s on S c i en t i f i c ,I n c
. ( www. t e c h s t r e e t . c om ) .T h i s c o p y d ownl o
a d e d on2 0 1 4 - 0 1 - 0 6 0 8 : 2 8 : 2 8 - 0 6 0 0 b y a u t h or i z e d u s er P h am V an c h i .
N of ur t h er r e pr o d u c t i on or d i s t r i b u t i oni s p er mi t t e d .
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– 54 – PAS 61975 © IEC:2004 (E)
3.2 Converter Station Tests Introduction
This group of tests includes HV energization of AC fillers, capacitor banks and
shunt reactors, open line test of the DC switchyard and load tests of theconverter station and back-to-back or short circuit test. If there are multiple
groups in each pole, they should be initially energized individually and then
together.
3.2.1 HV Energization of AC filters, Capacitor Banks and Shunt Reactors
Introduction
This section deals with the first energization of AC filters, capacitor banks andshunt reactors individually for the first time. Combined switching of these
elements is dealt with in 6.3.
Test Objectives
The test objective of the HV energization is to verify that proper voltage
insulation is achieved and that the AC filters, capacitor banks and shunt reactors
are balanced between the three phases and each phase for itself. Confirmationof the onload currents and voltages of the protections may be conducted at this
time.
Preconditions
Before conducting the HV energization the following preconditions shall be
fulfilled.
- All controls and protections (main and backup) associated with the highvoltage equipment shall be verified and in service. A trip test shall be made
shortly before high voltage energization.
- AC filter tuning shall be completed.
- AC filters and shunt capacitors shall have been balanced.
- All clamp joints shall have been tightened and the insulators wiped clean.
- All safety procedures shall have been carried out
C o p y r i gh t e d m a t er i al l i c en s e d t oE l e c t r i c i t y of V i e t n am b y T h om s on S c i en t i f i c ,I n c
. ( www. t e c h s t r e e t . c om ) .T h i s c o p y d ownl o
a d e d on2 0 1 4 - 0 1 - 0 6 0 8 : 2 8 : 2 8 - 0 6 0 0 b y a u t h or i z e d u s er P h am V an c h i .
N of ur t h er r e pr o d u c t i on or d i s t r i b u t i oni s p er mi t t e d .
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PAS 61975 © IEC:2004 (E) – 55 –
- A final visual inspection of the high voltage equipment shall be performed,
and the arrester counter numbers shall be recorded.
Test Procedure
During the test, AC voltage, steady-state and inrush-currents may be recorded.
Inspect the equipment during the test for abnormal sounds, corona discharge or
partial discharge arcing. The following test sequence is recommended.
- Energize the AC filters, capacitor banks and shunt reactors one by one.
- Keep each AC filter, capacitor bank and shunt reactor energized for a
minimum of 2 hours.
Test Acceptance Criteria
No abnormal sounds or corona discharge arcing shall occur in the energized
equipment. No protections shall operate improperly. The AC filters and capacitor
banks shall be balanced within design tolerances.
3.2.2 Open Line Test of the DC Switchyard Test Objectives
The test objective of the open line test of the DC switchyard is to verify that
proper insulation voltage withstand is achieved. This open line test will also
show that the converter firing control and the valve base electronics function
properly.
Preconditions
Before conducting the open line test the following preconditions must be fulfilled:
- The converter transformers shall have been energized,
- All controls and protections associated with the converter transformers and
the DC switchyard including the DC voltage dividers shall be verified and in
service. A trip test shall be made shortly before high voltage energization.
Preferably a low voltage energization shall have been performed.
C o p y r i gh t e d m a t er i al l i c en s e d t oE l e c t r i c i t y of V i e t n am b y T h om s on S c i en t i f i c ,I n c
. ( www. t e c h s t r e e t . c om ) .T h i s c o p y d ownl o
a d e d on2 0 1 4 - 0 1 - 0 6 0 8 : 2 8 : 2 8 - 0 6 0 0 b y a u t h or i z e d u s er P h am V an c h i .
N of ur t h er r e pr o d u c t i on or d i s t r i b u t i oni s p er mi t t e d .
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– 56 – PAS 61975 © IEC:2004 (E)
- Monitoring instrumentation shall be connected and ready.
- All clamp joints shall have been tightened and the insulators wiped clean.
- The HVDC transmission fine disconnect switch shall be opened and locked.
- All safety procedures shall have been carried out.
- A final visual inspection of the DC switchyard shall be performed and the
arrester counter numbers shall be recorded.
- DC filter tuning shall be completed.
Test Procedures
During the test, AC and DC voltage and current shall be recorded. Inspect the
equipment during the test for abnormal sounds, corona discharge or partial
discharge arcing. The following test sequence is recommended:
- Connect the neutral side of the converter to ground or the electrode (if
available).
- Energize the converter transformer at the lowest valve side voltage and step
the tap changers to rated voltage,
- Deblock the converter in the open fine test status of operation and ramp the
DC voltage slowly to rated value.
- Keep the DC equipment energized for a minimum of 2 h.
- After the successful completion of the test, decrease the DC voltage to zero
and block the converter.
- Repeat the open line test of the DC switchyard with the appropriate DC filters
connected one by one and then together.
- If there are multiple valve groups in each pole they should be initially
energized individually and then together.
Test Acceptance Criteria
No abnormal sounds or corona discharge shall occur in the energized
equipment. No protections shall operate improperly.
Confirm that the designed DC voltage can be achieved.
C o p y r i gh t e d m a t er i al l i c en s e d t oE l e c t r i c i t y of V i e t n am b y T h om s on S c i en t i f i c ,I n c
. ( www. t e c h s t r e e t . c om ) .T h i s c o p y d ownl o
a d e d on2 0 1 4 - 0 1 - 0 6 0 8 : 2 8 : 2 8 - 0 6 0 0 b y a u t h or i z e d u s er P h am V an c h i .
N of ur t h er r e pr o d u c t i on or d i s t r i b u t i oni s p er mi t t e d .
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PAS 61975 © IEC:2004 (E) – 57 –
3.2.3 Load Tests
3.2.3. 1 Back-to-Back Test
Introduction
For bipolar HVDC systems back-to-back testing may be considered since this
provides the least disturbance to the connected AC system. Back-to-back testing
is accomplished by operating a bipolar terminal with one converter as rectifier
and the other as inverter. The connection between the converters may be within
the station or may include part or all of the DC transmission circuit. In the latter
case it is recommended to conduct an open tine test of the transmission circuit,as described in 3.3, prior to the test. Back-to-back testing gives an effective
general check of converter operation up to the specified maximum load and is
preferably conducted at all converter terminate.
It shall be noted that the telecommunication system is not required for these
tests. Adjustments to the control system may be necessary.
Test Objectives
The test objective of the back-to-back test is to get a provisional verification of
the control system, the valve cooling capability and the main circuit with respect
to temperature rise.
The back-to-back tests do not reduce the end-to-end test requirements. The
tests should permit troubleshooting at the individual terminals to provide for a
more efficient end-to-end test procedure. Current control, power control andreactive power control checkout may be performed with each converter pole
operating both as rectifier and inverter.
Preconditions
Before beginning the tests, the following preconditions must be fulfilled:
- The energization tests of the AC filters, capacitor banks and shunt reactors
shall have been successfully completed.
C o p y r i gh t e d m a t er i al l i c en s e d t oE l e c t r i c i t y of V i e t n am b y T h om s on S c i en t i f i c ,I n c
. ( www. t e c h s t r e e t . c om ) .T h i s c o p y d ownl o
a d e d on2 0 1 4 - 0 1 - 0 6 0 8 : 2 8 : 2 8 - 0 6 0 0 b y a u t h or i z e d u s er P h am V an c h i .
N of ur t h er r e pr o d u c t i on or d i s t r i b u t i oni s p er mi t t e d .
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– 58 – PAS 61975 © IEC:2004 (E)
- The converter transformers, the valves (and the DC switchyard filters if
available) and switchgear shall have been energized.
- A temporary connection between the converter or a part of the DC
transmission circuit is required.- The DC-reactor shall be included in series with the converter units.
- Some control parameters may have to be temporarily adjusted for
back-to-back testing if appropriate.
- All safety procedures shall have been carried out.
Consideration must be given to a possible trip of the converters during testing. If
a trip occurs, a protection scheme shall ensure that the station AC bus is
adequately protected by limiting the level and duration of the voltage rise to
acceptable values. This may be achieved by putting a limit on maximum
allowable direct current. For AC systems with low short circuit ratio (refer to
CIGRE Planning Guide for weak AC-systems, Publication Number ..,) it is
recommended to install a tripping arrangement (if not already included) that
removes all filters should a converter block.
Test Procedure
The two converters must be temporarily interconnected. The interconnection
must be adequate for maximum test current. The reactive power should vary
with direct current similarity to expected values during end-to-end operation. The
harmonic AC filters and shunt banks shall be utilized to reduce maximum
variation of reactive power exchange with the AC network. Tests and
measurements should be made to verify:
- Deblocking and blocking of converters.
- Ramping up to maximum test current including check of current measuring
circuits.
- Proper functioning of current control, power control, automatic tap changer
control and reactive power control.
- The measured quantities for the AC-filters protection and for the transformer
protection. Make adjustments if necessary.
- Acceptable equipment temperatures and absence of hot spots.
C o p y r i gh t e d m a t er i al l i c en s e d t oE l e c t r i c i t y of V i e t n am b y T h om s on S c i en t i f i c ,I n c
. ( www. t e c h s t r e e t . c om ) .T h i s c o p y d ownl o
a d e d on2 0 1 4 - 0 1 - 0 6 0 8 : 2 8 : 2 8 - 0 6 0 0 b y a u t h or i z e d u s er P h am V an c h i .
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PAS 61975 © IEC:2004 (E) – 59 –
- Steady state and transient properties of the cooling system of the valves are
correct.
- Switching sequences in the auxiliary power system are correct and these
should be done initially at low DC-current levels.- Correct operation of redundancy arrangements, for instance by simulation of
faults in units or functions, where redundancy is built into the equipment
During back-to-back operation, even though the rectifier angle is kept close to
nominal, the angle may vary with different levels of direct currents and thus vary
the phase angle between the harmonics from the rectifier and the inverter. At
some point of operation some harmonics may be in phase opposition to each
other, which will result in the filter current being very small. This should be kept
in mind during the observation of loading of the AC filters.
Test Acceptance Criteria
Demonstration of proper converter operation.
Equipment temperatures shall be within specified limits. No hot spots may exist.
Initial assessment of the cooling capability of the thyristor valves, transformers,
reactors, building and valve hall shall demonstrate no abnormalities.
No protection shall operate improperly.
3.2.3.2 Short Circuit Test Introduction
The short circuit test may be conducted on a monopolar DC system or in caseswhere schedules or constraints do not allow both converters of a bipolar station
to be used for back-to-back testing.
Test Objective
To provide minimal verification of the control system before end-to-end testing.
C o p y r i gh t e d m a t er i al l i c en s e d t oE l e c t r i c i t y of V i e t n am b y T h om s on S c i en t i f i c ,I n c
. ( www. t e c h s t r e e t . c om ) .T h i s c o p y d ownl o
a d e d on2 0 1 4 - 0 1 - 0 6 0 8 : 2 8 : 2 8 - 0 6 0 0 b y a u t h or i z e d u s er P h am V an c h i .
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Preconditions
The preconditions for the short circuit test are the same as for the back-to-back
test, described in sections 3.2.3.1. The DC smoothing reactor must be includedin series with the converter unit when creating the short circuit.
The DC circuit must be operated short circuited with alpha at approximately 90
degree (Ud = 0) during this test. The large delay angle results in much higher
than normal losses in the valve circuits. As a precaution it is recommended to
limit the duration of the test and to have adequate cool down time between tests.
Control and protection systems that would have operated as a result of theconditions during the test must be disabled in a safe manner.
Test Procedure
The test should be made with the converter transformer tap changer in highest
position (lowest valve side voltage). Tests may be made to verify:
- Deblocking and blocking;- Current control stability;
- Response to a step change.
Test Acceptance Criteria
Demonstration of response and stability of the current control system.
C o p y r i gh t e d m a t er i al l i c en s e d t oE l e c t r i c i t y of V i e t n am b y T h om s on S c i en t i f i c ,I n c
. ( www. t e c h s t r e e t . c om ) .T h i s c o p y d ownl o
a d e d on2 0 1 4 - 0 1 - 0 6 0 8 : 2 8 : 2 8 - 0 6 0 0 b y a u t h or i z e d u s er P h am V an c h i .
N of ur t h er r e pr o d u c t i on or d i s t r i b u t i oni s p er mi t t e d .
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PAS 61975 © IEC:2004 (E) – 61 –
3.3 Open Line Test of the DC Transmission Circuit Introduction
Open line test of the DC transmission circuit can be performed from either end of
the HVDC system but one at a time, it is normally done from the converter thatbecomes first available but preferably from the terminal with the highest
operating voltage. The open line test is an excellent test to demonstrate the
condition of the HVDC line and cables. Both short-circuit and open line
conditions can be detected over the entire length of the circuit.
The open line test is mainly conducted to verify the insulation of the DC
transmission circuit prior to transmitting power. The test is not only important for
the initial start up of the System but may also be used for test purposes following
a permanent fault on the system before returning to commercial operation.
Test Objectives
The test objective is to verify that the HVDC transmission circuit is not opened or
grounded anywhere over its entire length. The open line test should also verify
that proper voltage insulation of the DC transmission circuit is achieved.
Preconditions
Before conducting the open line lest the following preconditions shall be fulfilled.
- The DC switchyard shall have been successfully energized.
- All control and protection systems shall have been verified and be
operational.
- The DC transmission circuit shall be available.
- Check that the other terminal is isolated.
- Voice communication system shall be in service.
- All safety procedures shall have been carried out.
- The neutral side of the converter shall be connected to the earth electrode
and the high voltage side to the line or cable.
C o p y r i gh t e d m a t er i al l i c en s e d t oE l e c t r i c i t y of V i e t n am b y T h om s on S c i en t i f i c ,I n c
. ( www. t e c h s t r e e t . c om ) .T h i s c o p y d ownl o
a d e d on2 0 1 4 - 0 1 - 0 6 0 8 : 2 8 : 2 8 - 0 6 0 0 b y a u t h or i z e d u s er P h am V an c h i .
N of ur t h er r e pr o d u c t i on or d i s t r i b u t i oni s p er mi t t e d .
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Test Procedures
During the test AC and DC voltage and current shall be recorded. Inspect the
switchyard equipment during the test for abnormal sounds or corona discharge.The following test sequence is recommended.
- Apply a ground to the remote end of the DC line or cable,
- Energize the converter transformer and step the tap changers to rated
voltage.
- Deblock the converter in open line test status of operation and try to ramp
the DC voltage. If this is possible, the DC transmission circuit is opened
somewhere.
- Block the converter, deenergize the converter transformer and remove the
grounding at the remote end.
- Energize the converter transformer and step the tap changer to rated
voltage.
- Deblock the converter in open line test status of operation and slowly ramp
the DC voltage up to the desired level. Make sure that the DC voltage level
does not exceed the voltage insulation level at the other end.
- After the successful completion of the test, decrease the DC voltage to zero
and block the converter.
- Repeat the test for each line or cable and each polarity, if applicable.
- Keep the DC transmission circuit energized for a minimum of 2 h.
Test Acceptance Criteria
No protections shall operate improperly.
The DC voltage shall build up when the fine ground connection at the remote
end is removed.
C o p y r i gh t e d m a t er i al l i c en s e d t oE l e c t r i c i t y of V i e t n am b y T h om s on S c i en t i f i c ,I n c
. ( www. t e c h s t r e e t . c om ) .T h i s c o p y d ownl o
a d e d on2 0 1 4 - 0 1 - 0 6 0 8 : 2 8 : 2 8 - 0 6 0 0 b y a u t h or i z e d u s er P h am V an c h i .
N of ur t h er r e pr o d u c t i on or d i s t r i b u t i oni s p er mi t t e d .
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PAS 61975 © IEC:2004 (E) – 63 –
PART 4: END-TO-END-TESTS
General
Introduction
The end-to-end tests constitute a basic set of verifications at low power that are
to be conducted when the converter terminals are connected for the first time by
the DC transmission circuit
Since power will be transmitted, tests must be arranged to limit the potentialimpact to the HVDC system equipment and to the interconnected AC systems.
It will be necessary to perform end-to-end tests in all applicable HVDC system
configurations. The general test procedure is shown in the flow chart of
Figure 4.1.
It is necessary that some verifications are done off voltage or "dry" prior to
testing at any power level In particular the transfer between different DCsystem configurations and the verification of protective tripping sequences
should be done "dry", before tests at minimum power transfer level can start.
The HVDC system may be operated in the following different configurations:
- Monopolar Earth Return;
- Monopolar Metallic Return;
- Bipolar Operation;- Integration of Parallel or Series Converters.
C o p y r i gh t e d m a t er i al l i c en s e d t oE l e c t r i c i t y of V i e t n am b y T h om s on S c i en t i f i c ,I n c
. ( www. t e c h s t r e e t . c om ) .T h i s c o p y d ownl o
a d e d on2 0 1 4 - 0 1 - 0 6 0 8 : 2 8 : 2 8 - 0 6 0 0 b y a u t h or i z e d u s er P h am V an c h i .
N of ur t h er r e pr o d u c t i on or d i s t r i b u t i oni s p er mi t t e d .
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The following tests are outlined:
4.1 Changing the DC system configurations, off voltage.
4.2 Start and stop sequences and Steady State Operation at minimum power.4.3 Protective Blocking and Tripping Sequences.
4.4 Power and current ramping.
4.5 Reduced Voltage Operation.
If no back-to-back test has been performed, verification of the performance of
the valve cooling system must be done as power is increased.
The operating conditions of the HVDC system can be:
- Normal operation. This includes synchronous and islanded operation if
applicable.
- Contingency operation, which exists if a single failure occurs but the HVDC
system can continue operation within specified limits. Loss of telecom
represents a typical example.
- Emergency operation as per project specific definitions. This does not
normally need to be tested in the actual system during commissioning.
However it is advisable to test during off-site testing.
Operator control actions can be initiated from various locations. Such typical
locations are:
- Local control, which applies when the control functions can be initiated from
the local control room at either converter terminal.
- Remote control, which applies when the control functions can be initiated
from a control centre remote from either converter terminal.
The operator can accomplish a change of operational status by using one of two
different control methods:
- Automatic Control
- Manual Control
C o p y r i gh t e d m a t er i al l i c en s e d t oE l e c t r i c i t y of V i e t n am b y T h om s on S c i en t i f i c ,I n c
. ( www. t e c h s t r e e t . c om ) .T h i s c o p y d ownl o
a d e d on2 0 1 4 - 0 1 - 0 6 0 8 : 2 8 : 2 8 - 0 6 0 0 b y a u t h or i z e d u s er P h am V an c h i .
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PAS 61975 © IEC:2004 (E) – 65 –
In automatic control the operator initiates a change of operational status, a
change of configuration or a change of power (current) reference selection and
the respective controls execute the correct order. The successful completion is
verified by monitoring.
In Manual, the control of the converter terminal is performed in discrete steps
from one operational status to another. Compared to the automatic control
mode, the operator is offered a choice of additional intermediate steps and
intervention in the control sequences. Completion of any control sequence will
be verified by monitoring.
The control level denotes the hierarchical level of HVDC system control. A
distinction is made between:
- System control level (Joint control available).
- Station or Bipole control level (Joint or Separate control Available).
- Pole or Converter control level (Joint or Separate control available).
At the System control level the complete HVDC system can be controlled jointly
from one of the remote or local operator control locations, hencetelecommunication is required at this level.
At the Station (or Bipole) control levels each HVDC station/Bipole is controlled
separately when telecommunication is not available. The stations can be jointly
controlled from one location when telecommunication is available.
At the Pole (or Converter) control level each pole/converter is controlled
separately when telecommunication is not available. The poles of the twostations can be jointly controlled from one location when telecommunication is
available.
C o p y r i gh t e d m a t er i al l i c en s e d t oE l e c t r i c i t y of V i e t n am b y T h om s on S c i en t i f i c ,I n c
. ( www. t e c h s t r e e t . c om ) .T h i s c o p y d ownl o
a d e d on2 0 1 4 - 0 1 - 0 6 0 8 : 2 8 : 2 8 - 0 6 0 0 b y a u t h or i z e d u s er P h am V an c h i .
N of ur t h er r e pr o d u c t i on or d i s t r i b u t i oni s p er mi t t e d .
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General Preconditions
The following activities must have been completed before the end-to-end tests
can proceed: Off-site Tests.
Converter Tests for both stations.
Back-to-back Test or Short Circuit Tests when possible,
Open Line Test of the DC transmission circuit.
Electrodes and electrode lines checked and cleared.
Telecommunication system and telephone system operational.
The overall test procedures, safety rules, dispatch coordination and test
responsibilities have been established.
Fire protection and detection systems have been fully checked and in service.
All Control, Protection, Metering, Sequence of Events and Fault Recording
systems must be in service.
General Test Objectives
End-to-end tests are intended to verify the proper co-ordination and interstation
interlocking of the basic HVDC control and protection functions at low power
levels. The tests shall be performed with various AC and DC system
configurations and for applicable contingencies. Changing the DC system
configuration (as described in part 6) or the status of operation for the first time
must be tested without high voltage (Dry Run Test or Off Voltage Test),
The tests should be organized in such a way that all the control modes, control
levels and control locations will be tested without unnecessary duplication of
tests.
C o p y r i gh t e d m a t er i al l i c en s e d t oE l e c t r i c i t y of V i e t n am b y T h om s on S c i en t i f i c ,I n c
. ( www. t e c h s t r e e t . c om ) .T h i s c o p y d ownl o
a d e d on2 0 1 4 - 0 1 - 0 6 0 8 : 2 8 : 2 8 - 0 6 0 0 b y a u t h or i z e d u s er P h am V an c h i .
N of ur t h er r e pr o d u c t i on or d i s t r i b u t i oni s p er mi t t e d .
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PAS 61975 © IEC:2004 (E) – 67 –
4.1 Changing the DC System Configuration, OFF-Voltage
Introduction
Changing the DC system configuration can be relatively simple in a point to point
system which has a single converter per pole. The switching operations become
more complicated if the station poles have parallel or series converters. This test
is intended to demonstrate that equipment, breakers, disconnects or grounding
switches are operated in the correct sequence and, are properly interlocked.
Changing the DC system configuration on load is described in part 6.
Transfers between different DC system configurations can be initiatedautomatically and jointly or manually from local control or from a remote dispatch
centre. In manual or separate control, the operators need to coordinate these
actions via voice communication.
Test Objectives
The purpose of the tests is to verify that the DC system configuration can be
safely changed as specified prior to transmitting power for the first time.
Preconditions
Before conducting the test the following preconditions must be fulfilled:
- Off-site tests verifying DC system configuration change shall have beencompleted.
- All necessary AC and DC switching equipment shall be operational.
- Operator instructions and test procedures shall be available.
C o p y r i gh t e d m a t er i al l i c en s e d t oE l e c t r i c i t y of V i e t n am b y T h om s on S c i en t i f i c ,I n c
. ( www. t e c h s t r e e t . c om ) .T h i s c o p y d ownl o
a d e d on2 0 1 4 - 0 1 - 0 6 0 8 : 2 8 : 2 8 - 0 6 0 0 b y a u t h or i z e d u s er P h am V an c h i .
N of ur t h er r e pr o d u c t i on or d i s t r i b u t i oni s p er mi t t e d .
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Test Procedures
The transfer between specified DC System configurations shall be
demonstrated. The most logical approach is to perform the changes ofconfiguration from the initial conditions defined below:
- Monopolar earth return.
- Monopolar metallic return.
- Bipolar operation.
- Integration of parallel or series converters.
The tests shall first be performed with telecommunication out of service, andthen with telecommunication in service:
- Establish voice communication with the operator of the other terminal.
- Switch off the telecommunication.
- Reset all alarms.
- Select the initial DC system configuration in accordance with the operating
instructions. The procedure will have to be done in steps involving operators
at both terminals.
- Verify the appropriate switching action on the operator control interface and
sequence of events recorder. Simulate failures in the Switching Sequence.
- Repeat the test for all applicable DC system configurations.
- Restore telecommunication.
- Repeat the tests, now in automatic and joint control mode.
Test Acceptance Criteria
- Switching sequences shall correctly transfer between all applicable DC
system configurations, with and without telecommunication.
- All Switching sequences shall be safely and correctly completed.
- The interlocking of disconnectors, switches and breakers of the AC and DC
yards shall be in accordance with the technical specifications.
- It should be possible to initiate a change of DC system configuration from
local and, if available, from remote control locations.
- An incomplete sequence shall be terminated in a safe condition.
C o p y r i gh t e d m a t er i al l i c en s e d t oE l e c t r i c i t y of V i e t n am b y T h om s on S c i en t i f i c ,I n c
. ( www. t e c h s t r e e t . c om ) .T h i s c o p y d ownl o
a d e d on2 0 1 4 - 0 1 - 0 6 0 8 : 2 8 : 2 8 - 0 6 0 0 b y a u t h or i z e d u s er P h am V an c h i .
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PAS 61975 © IEC:2004 (E) – 69 –
4.2 Start and Stop Sequences and Steady State Operation at Minimum
Power
Introduction
Great care must be exercised when going through the start and stop sequences
for the first time. The thyristor valves will be deblocked at the rectifier and
inverter end and current will be established in the DC transmission circuit.
The sequences for starting and stopping the converters are not identical for all
HVDC systems and can vary depending upon the design philosophies of the
supplier and the system requirements of the customer. The general sequence of
bringing a converter from STOPPED status to DEBLOCKED is defined below.
- The STOPPED status is generally characterized by the following conditions:
Converter control and protection may be energized or de-energized;
Valve cooling system switched off;
Transformer and smoothing reactor cooling systems switched off;
Tap changer control inhibited;
Converter transformer circuit breaker open;
DC filter disconnector can be open;
AC filter circuit breaker open;
Firing pulses to the converter blocked.
- The STAND-BY (or DE-ENERGIZED) status is generally characterized by
the following conditions: Converter Control and protection must be energized;
Valve cooling system switched on;
Transformer and smoothing reactor cooling systems switched on;
Power or current control setpoint selection available;
Tap changer operational and in correct position;
AC filter disconnector closed, circuit breaker open;
C o p y r i gh t e d m a t er i al l i c en s e d t oE l e c t r i c i t y of V i e t n am b y T h om s on S c i en t i f i c ,I n c
. ( www. t e c h s t r e e t . c om ) .T h i s c o p y d ownl o
a d e d on2 0 1 4 - 0 1 - 0 6 0 8 : 2 8 : 2 8 - 0 6 0 0 b y a u t h or i z e d u s er P h am V an c h i .
N of ur t h er r e pr o d u c t i on or d i s t r i b u t i oni s p er mi t t e d .
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– 70 – PAS 61975 © IEC:2004 (E)
DC filter disconnector closed;
Converter Transformer disconnector closed, circuit breaker open.
- The BLOCKED (or READY FOR OPERATION) status is generally
characterized by the following conditions:
Converter transformer circuit breaker closed;
Tap changer control activated;
AC filter circuit breaker open or closed ;
Thyristor precheck completed.
- The DEBLOCKED status is generally characterized by the following
conditions:
AC filter circuit breakers closed;
Valve Firing pulses deblocked;
Rectifier and/or inverter in operation.
Test Objectives
The general purpose of this test is to deblock both converters of the HVDC
transmission system and transmit minimum power for the first time, in both
directions if applicable. Other purposes are to:
Verify for each pole, that control actions associated with each status change,
start and stop sequences are executed in the right order.
Verify, that minimum power can be established and stopped smoothly and
reliably in all applicable HVDC system configurations.
Verify correct system measurements during steady state operation at
minimum power.
C o p y r i gh t e d m a t er i al l i c en s e d t oE l e c t r i c i t y of V i e t n am b y T h om s on S c i en t i f i c ,I n c
. ( www. t e c h s t r e e t . c om ) .T h i s c o p y d ownl o
a d e d on2 0 1 4 - 0 1 - 0 6 0 8 : 2 8 : 2 8 - 0 6 0 0 b y a u t h or i z e d u s er P h am V an c h i .
N of ur t h er r e pr o d u c t i on or d i s t r i b u t i oni s p er mi t t e d .
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PAS 61975 © IEC:2004 (E) – 71 –
Preconditions
Before conducting the tests some preconditions must be fulfilled:
The DC system configuration has been established by means of a
successful off-voltage test.
Off-site tests for start and stop sequences have been successfully completed.
Converter tests for both stations have been successfully completed.
Appropriate AC and DC filters are available.
The valve cooling equipment has been verified and is operational.
No alarm are present.
Thyristor monitoring shows thyristor redundancy is not exceeded.
Protective blocking and tripping sequences should have been successfully
tested off voltage. All protective lockouts shall have been reset.
Operator's instructions and lest procedures shall be available.
The connected AC systems shall be capable of delivering or accepting the
transmitted power without affecting their stable operation.
Test Procedure
The start and stop test must be preceded by establishment of one of the AC and
DC system configurations off voltage. The test must then be repeated for all
applicable system configurations and in both synchronous and islanded operation.
- When the HVDC system configuration is established, the operational status
can be tested beginning with "stopped" or "stand-by". This change of status
is done off voltage. By changing the operational status for both ends to
"blocked", voltage will be applied to the converters.
- Establish voice communication between the operators at each end and put
telecommunication out of service.
- Establish operation at minimum power by first deblocking the inverter and
then the rectifier.
- Remain at minimum power for a short period. Then block the rectifier and the
inverter.- Restore telecommunication.
C o p y r i gh t e d m a t er i al l i c en s e d t oE l e c t r i c i t y of V i e t n am b y T h om s on S c i en t i f i c ,I n c
. ( www. t e c h s t r e e t . c om ) .T h i s c o p y d ownl o
a d e d on2 0 1 4 - 0 1 - 0 6 0 8 : 2 8 : 2 8 - 0 6 0 0 b y a u t h or i z e d u s er P h am V an c h i .
N of ur t h er r e pr o d u c t i on or d i s t r i b u t i oni s p er mi t t e d .
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– 72 – PAS 61975 © IEC:2004 (E)
- Establish operation at minimum power in automatic and joint mode. Remain
at minimum power for at least 1 h and verify measurements of DC currents,
voltage etc. It is advisable to perform switching of redundant controls and
other elements at minimum power level in order to verify that there is no
impact on the HVDC transmission or the AC network.
- Special attention shall be given throughout the test to verify that no hot spots
develop. The equipment inside the valve hall, the converter transformers,
smoothing reactors and the wall bushings are among the critical items to
check. Also verify that the valve cooling system maintains the valve
temperature within specified limits.
- If applicable, transmission of power in the reverse direction shall be tested.
Test Acceptance Criteria
- Starting and stopping at minimum power must be safely and reliably
accomplished in each applicable HVDC system configuration.
- All control actions shall take place in correct order and timing. Interstation
interlocking shall function properly.
- No malfunction may occur.
- Equipment rating shall not be exceeded.
- No AC and DC system disturbance may occur.
- The cooling system shall keep the valve temperature within specified limits.
- Switching between redundant elements shall have no impact on the HVDC
transmission.
C o p y r i gh t e d m a t er i al l i c en s e d t oE l e c t r i c i t y of V i e t n am b y T h om s on S c i en t i f i c ,I n c
. ( www. t e c h s t r e e t . c om ) .T h i s c o p y d ownl o
a d e d on2 0 1 4 - 0 1 - 0 6 0 8 : 2 8 : 2 8 - 0 6 0 0 b y a u t h or i z e d u s er P h am V an c h i .
N of ur t h er r e pr o d u c t i on or d i s t r i b u t i oni s p er mi t t e d .
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PAS 61975 © IEC:2004 (E) – 73 –
4.3 Protective Blocking and Tripping Sequences
Introduction
HVDC systems can be exposed to various types of faults of permanent or
temporary nature.
Depending on the type of fault, the protective blocking and tripping sequence
may result in some combination of the following actions:
- Instantaneous advancing of the inverter firing angle (commutation failures);
- Transfer to redundant control (if applicable);
- Retarding the firing angle of the rectifier;
- Blocking of the converter valves blocking (with or without selection of by-
pass pairs);
- AC breaker tripping (converter transformers and possibly AC filters);
- Pole isolation by opening DC switches;
- Blocking of remote station.
Protective control sequences may also be initiated as a consequence of load
rejection.
Test Objectives
Verify that proper blocking or protective tripping sequences take place
selectively when clearing a fault or equipment malfunction.
Verify that DC protective actions are properly co-ordinated with the AC
breaker
operation and other protections,
Verify that control actions reestablish system transmission as specified.
C o p y r i gh t e d m a t er i al l i c en s e d t oE l e c t r i c i t y of V i e t n am b y T h om s on S c i en t i f i c ,I n c
. ( www. t e c h s t r e e t . c om ) .T h i s c o p y d ownl o
a d e d on2 0 1 4 - 0 1 - 0 6 0 8 : 2 8 : 2 8 - 0 6 0 0 b y a u t h or i z e d u s er P h am V an c h i .
N of ur t h er r e pr o d u c t i on or d i s t r i b u t i oni s p er mi t t e d .
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– 74 – PAS 61975 © IEC:2004 (E)
Preconditions
The co-ordination between the protective systems and the control systems
shall have been demonstrated during off site tests.
The AC and DC protection systems have been exercised during subsystem
and converter station tests.
All redundant control and protection systems are in service.
All monitoring and alarm systems are in service.
Test personnel are well informed on each protection and on the protective
actions to expect.
Telecommunication system is in service.
The connected AC systems shall be capable of delivering or accepting the
transmitted power without affecting their stable operation.
The AC and DC equipment are energized.
Test Procedure
In order to verify the proper function of a protective blocking or tripping sequence
the faults will have to be simulated.
It is advisable that testing the protective sequences begins with tests off voltage.
After successful completion of the off voltage tests, trips shall be simulated at
minimum power in all applicable system configurations and with the
telecommunication system in and out of operation.
The following signals shall be recorded:
- AC voltages and currents on each phase;
- DC voltages on both poles;
- AC currents in the Valve winding on each phase;
- DC currents on each pole and on each DC neutral connection;
- AC currents in filter banks;
- Main sequencing signals;
C o p y r i gh t e d m a t er i al l i c en s e d t oE l e c t r i c i t y of V i e t n am b y T h om s on S c i en t i f i c ,I n c
. ( www. t e c h s t r e e t . c om ) .T h i s c o p y d ownl o
a d e d on2 0 1 4 - 0 1 - 0 6 0 8 : 2 8 : 2 8 - 0 6 0 0 b y a u t h or i z e d u s er P h am V an c h i .
N of ur t h er r e pr o d u c t i on or d i s t r i b u t i oni s p er mi t t e d .
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PAS 61975 © IEC:2004 (E) – 75 –
- Protection signals;
- Firing and extinction angles order and measurements;
- Current order.
During each simulated fault, test personnel must check that the correct circuit
breaker trips and that the corresponding alarm and sequence of event recorder
signals are initiated.
Operators must confirm that both terminals are stopped safely.
Test Acceptance Criteria
For each simulated fault, the corresponding protective blocking and tripping
sequence shall operate in accordance with the technical specifications and
system studies.
The consequential outages of a fault must be limited to the smallest possible
zone and properly isolated from the rest of the HVDC system.
Correct alarms are announced, sequence of event recorder and transient faultrecorder should show that the correct sequence has taken place.
Safe isolation of a pole and/or converter is accomplished with and without
telecommunication.
The impact to the HVDC system and the connected AC systems must be within
specified Performance Criteria.
C o p y r i gh t e d m a t er i al l i c en s e d t oE l e c t r i c i t y of V i e t n am b y T h om s on S c i en t i f i c ,I n c
. ( www. t e c h s t r e e t . c om ) .T h i s c o p y d ownl o
a d e d on2 0 1 4 - 0 1 - 0 6 0 8 : 2 8 : 2 8 - 0 6 0 0 b y a u t h or i z e d u s er P h am V an c h i .
N of ur t h er r e pr o d u c t i on or d i s t r i b u t i oni s p er mi t t e d .
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– 76 – PAS 61975 © IEC:2004 (E)
4.4 Power and Current Ramping
Introduction
This test is intended to demonstrate that the HVDC system power can be
smoothly ramped up from minimum power to approximately 0,3 pu. and down, in
both power and current control. The test is normally conducted with
telecommunication in service. However, if applicable, ramping shall also be
demonstrated with telecommunication out of service.
Test Objectives
The general purpose of this test is to verily that smooth ramping at different rates
can be executed for each pole and, if applicable, for the bipole. It is also to verify
that:
- Transfer between operation with and without telecommunication is smooth.
- Transfer between power and current control is smooth.
Preconditions
To perform the ramping test, the following preconditions should apply:
- The HVDC system has been energized and operated at minimum rated
current;
- The protective blocking and tripping sequences have been verified;
- The connected AC systems shall be capable of delivering or accepting thetransmitted power without affecting their stable operation.
Test Procedure
The ramping test shall be performed in monopolar metallic and ground return
configuration for each pole and then, if applicable, in bipolar operation.
If possible, ramping shall first be tested without telecommunication in service.
C o p y r i gh t e d m a t er i al l i c en s e d t oE l e c t r i c i t y of V i e t n am b y T h om s on S c i en t i f i c ,I n c
. ( www. t e c h s t r e e t . c om ) .T h i s c o p y d ownl o
a d e d on2 0 1 4 - 0 1 - 0 6 0 8 : 2 8 : 2 8 - 0 6 0 0 b y a u t h or i z e d u s er P h am V an c h i .
N of ur t h er r e pr o d u c t i on or d i s t r i b u t i oni s p er mi t t e d .
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PAS 61975 © IEC:2004 (E) – 77 –
Having established voice communication operators deblock the converters
individually and allow the HVDC system current to stabilize at its minimum rated
value.
- Operate at this current level for a short time. The current can then be ramped
to the next preselected level. The system is again allowed to settle. This
procedure is repeated until the current has reached 0,3 pu.
- Special attention shall be given throughout the test to all current paths to
verify that no hot spots develop. The equipment inside the valve hall, the
converter transformers, smoothing reactors and the wall bushings are among
the critical items to check. Also verity that the valve cooling system maintains
the valve temperature within specified limits.
- Ramp down to minimum current and restore telecommunication.
- Repeat the above test in automatic control mode and joint control.
- Transfer to power control and repeat the test.
Test Acceptance Criteria
The following test acceptance criteria shall be fulfilled.
- Smooth ramping of the HVDC system current and power shall be possible for
all applicable DC system configurations.
- AC and DC currents and voltages shall at all times be stable and remain
within specified limits. Verify the control system keeps the firing angle within
specified limits and that transformer tap changer control operates correctly.
- No hot spots should occur in the AC and DC yard equipment or in the valvehall.
- The valve cooling system maintains the valve temperature within specified
limits. Smooth transfer between current and power control or vice versa.
- If applicable, it should also be verified that the control system schedules the
necessary reactive power elements in the appropriate order to keep the AC
voltage and reactive power interchange within the specified limits.
C o p y r i gh t e d m a t er i al l i c en s e d t oE l e c t r i c i t y of V i e t n am b y T h om s on S c i en t i f i c ,I n c
. ( www. t e c h s t r e e t . c om ) .T h i s c o p y d ownl o
a d e d on2 0 1 4 - 0 1 - 0 6 0 8 : 2 8 : 2 8 - 0 6 0 0 b y a u t h or i z e d u s er P h am V an c h i .
N of ur t h er r e pr o d u c t i on or d i s t r i b u t i oni s p er mi t t e d .
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– 78 – PAS 61975 © IEC:2004 (E)
4.5 Reduced Voltage Operation
Introduction
Manual or Automatic reduction of the DC voltage may be required to reduce
stresses on cables when the power transfer level is reduced, or to minimize the
possibility of flashover of overhead DC lines during adverse weather conditions
or conditions of excessive contamination.
Test Objectives
The purpose of the test is to verify that transfer to and from reduced voltage
operation, and that steady state operation at reduced voltage can take place in a
stable manner.
Preconditions
Before conducting reduced voltage tests the following preconditions must be
fulfilled.
- Off-site tests with reduced voltage operation successfully completed.
- The DC transmission has been operated at nominal voltage.
- The power and current ramping tests have been completed.
- The telecommunication should be in service.
C o p y r i gh t e d m a t er i al l i c en s e d t oE l e c t r i c i t y of V i e t n am b y T h om s on S c i en t i f i c ,I n c
. ( www. t e c h s t r e e t . c om ) .T h i s c o p y d ownl o
a d e d on2 0 1 4 - 0 1 - 0 6 0 8 : 2 8 : 2 8 - 0 6 0 0 b y a u t h or i z e d u s er P h am V an c h i .
N of ur t h er r e pr o d u c t i on or d i s t r i b u t i oni s p er mi t t e d .
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Fi ure 4.1 – Se uence for end-to-end tests
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– 80 – PAS 61975 © IEC:2004 (E)
Test Procedure
Reduced voltage operation shall be tested in all AC and DC system
configurations.- Start the DC transmission to minimum current and nominal voltage. Transfer
to reduced voltage operation and maintain steady state condition for one
hour. Transfer back to nominal voltage operation. Both manual and
automatic initiated transfer to reduced voltage operation (e.g. after DC line
faults) should be tested.
- Repeat the test at a higher current level.
- Repeat the test in power control.
- Correct functioning of the control system and adequate performance of the
valve cooling system should be observed for all current levels.
Test Acceptance Criteria
- Transfer to and from reduced voltage operation takes place smoothly and
does not disturb the connected AC network.- Steady state operation with reduced voltage is stable.
C o p y r i gh t e d m a t er i al l i c en s e d t oE l e c t r i c i t y of V i e t n am b y T h om s on S c i en t i f i c ,I n c
. ( www. t e c h s t r e e t . c om ) .T h i s c o p y d ownl o
a d e d on2 0 1 4 - 0 1 - 0 6 0 8 : 2 8 : 2 8 - 0 6 0 0 b y a u t h or i z e d u s er P h am V an c h i .
N of ur t h er r e pr o d u c t i on or d i s t r i b u t i oni s p er mi t t e d .
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PAS 61975 © IEC:2004 (E) – 81 –
PART 5: STEADY-STATE PERFORMANCE AND INTERFERENCE TESTS
General
Introduction
In this part HVDC system steady-state performance and interference tests are
described- These are system tests which seek to verify steady-state
performance parameters of the HVDC system and verify that electrical and
audible noise interference caused by the HVDC system are within specified
limits. It is important to coordinate in advance with all parties that may be
affected by operation of the HVDC system. For these steady-state and
interference tests, such parties may include telephone utilities, railroad
companies, pipeline companies, etc.. Steady-state performance and interference
tests are normally performed prior to the operation and integration tests.
Previous commissioning tests, including converter tests and end-to-end tests,
have verified that the DC equipment being commissioned functions correctly.
The following tests are outlined:
5.1 Harmonic performance and filter components rating
5.2 Audible noise
5.3 Overload/temperature rise
5.4 Interference
5.5 Earth electrode
C o p y r i gh t e d m a t er i al l i c en s e d t oE l e c t r i c i t y of V i e t n am b y T h om s on S c i en t i f i c ,I n c
. ( www. t e c h s t r e e t . c om ) .T h i s c o p y d ownl o
a d e d on2 0 1 4 - 0 1 - 0 6 0 8 : 2 8 : 2 8 - 0 6 0 0 b y a u t h or i z e d u s er P h am V an c h i .
N of ur t h er r e pr o d u c t i on or d i s t r i b u t i oni s p er mi t t e d .
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– 82 – PAS 61975 © IEC:2004 (E)
General Preconditions
The following activities should have been completed before the Steady-State
Performance and Interference Tests can proceed:
• Commissioning tests of ail converter units.
• Commissioning tests of transmission system as required for stable operation.
• Commissioning tests of reactive power control system.
Statement of Purpose
The purpose of the Steady-State Performance and Interference Tests is to verify
stable operation of the HVDC system within the limits given by the specifications
and verification of environmental considerations.
General Test Objectives
Steady-State Performance and Interference Tests are intended to verify that the
AC and DC harmonic levels, audible noise/corona and interference levels
conform with the specified levels. In addition, the tests verify the
overload/temperature rise and earth electrode performance conform with the
design targets.
C o p y r i gh t e d m a t er i al l i c en s e d t oE l e c t r i c i t y of V i e t n am b y T h om s on S c i en t i f i c ,I n c
. ( www. t e c h s t r e e t . c om ) .T h i s c o p y d ownl o
a d e d on2 0 1 4 - 0 1 - 0 6 0 8 : 2 8 : 2 8 - 0 6 0 0 b y a u t h or i z e d u s er P h am V an c h i .
N of ur t h er r e pr o d u c t i on or d i s t r i b u t i oni s p er mi t t e d .
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PAS 61975 © IEC:2004 (E) – 83 –
5.1 Harmonic Performance and Filter Components Rating
Introduction
The power conversion process in HVDC systems results in the generation of harmon-
ic currents and voltages which can affect the interconnected AC systems, DC
network, and third party electrical systems. Factors considered in the design and
harmonic studies of HVDC systems to minimize the level of harmonics propagated
from the HVDC system into the AC and DC network include the following:
AC system network impedance.
Harmonic frequencies of concern (characteristic and uncharacteristic).
Harmonic magnification (resonance) on the AC network.
Valve firing angle.
Converter transformer reactance and firing angle unbalance.
Unbalanced impedances of AC system and harmonic filters.
Transformer saturation effects and stray capacitance,
AC system distortion and interference limits.
Sensitivity of adjacent open-wire systems.
HVDC control system instabilities and interactions with other active devices.
Pre-existing harmonics on the AC network.
HVDC configuration and ground resistivity.
Ambient temperature range.
Phase angle relationship between AC systems.
AC and DC filter design.
AC harmonic filters connected to the AC bus reduce the harmonic voltages
appearing on the interconnected AC network and the harmonic currents injected
into the AC network to specified levels.
For HVDC systems with overhead transmission lines, smoothing reactors
together with DC filtering circuits are typically installed in the DC circuit to
reduce the harmonic currents to levels which will prevent interference with third
party telephone or electrical systems.
C o p y r i gh t e d m a t er i al l i c en s e d t oE l e c t r i c i t y of V i e t n am b y T h om s on S c i en t i f i c ,I n c
. ( www. t e c h s t r e e t . c om ) .T h i s c o p y d ownl o
a d e d on2 0 1 4 - 0 1 - 0 6 0 8 : 2 8 : 2 8 - 0 6 0 0 b y a u t h or i z e d u s er P h am V an c h i .
N of ur t h er r e pr o d u c t i on or d i s t r i b u t i oni s p er mi t t e d .
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– 84 – PAS 61975 © IEC:2004 (E)
The loading of the AC and DC harmonic filters must be checked and the filter
components ratings verified.
Test Objectives
The objective of the harmonic tests is to confirm that the harmonic voltages and
currents produced by the HVDC system are reduced by the AC and DC filters to
conform to specified limits and verify the harmonics do not cause unacceptable
interference with third party telephone or electrical systems. Additionally, the
tests demonstrate that harmonic performance is acceptable when operated in
various configurations and under required contingency modes.
The loading of the filter components shall be verified to be within the individual
component ratings.
Preconditions
Before conducting the tests the following preconditions must be fulfilled:
AC network conditions within specified limits.
Study results available which estimate the levels and spectrum of harmonics
from the HVDC system.
AC and DC filter design study results available.
Inductive coordination study results available.
Measurements available which establish pre-existing background levels and
spectrum of harmonic levels.
Precommissioning test data available for the AC and DC filter parameters.
Test instrumentation and data acquisition system available.
Specialized harmonic measuring equipment available.
Test Procedures
The harmonic measurements should be performed in those HVDC system
configurations and modes of operation which are specified. A test plan which
identifies these configurations and modes of operation along with the physical
locations for the harmonic measurements should be established, considering the
C o p y r i gh t e d m a t er i al l i c en s e d t oE l e c t r i c i t y of V i e t n am b y T h om s on S c i en t i f i c ,I n c
. ( www. t e c h s t r e e t . c om ) .T h i s c o p y d ownl o
a d e d on2 0 1 4 - 0 1 - 0 6 0 8 : 2 8 : 2 8 - 0 6 0 0 b y a u t h or i z e d u s er P h am V an c h i .
N of ur t h er r e pr o d u c t i on or d i s t r i b u t i oni s p er mi t t e d .
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PAS 61975 © IEC:2004 (E) – 85 –
following HVDC system operating conditions:
Stand-by operation.
Operation at minimum and rated power and at each power level which
initiates switching of a filter or reactive power component, and overloadHVDC power transfer levels.
Various HVDC and AC system configurations.
Any special condition generating maximum harmonics.
Reduced HVDC voltage operation.
Normal operation with specified filter configurations.
Operation at larger-than-normal firing angles. Operation with filter banks or reactive power banks unavailable.
Steady-state range of AC power frequency and voltage.
Extremes of ambient (as far as possible).
Automatic filter tuning.
DC harmonics testing should consider the following additional items:
Equipment safety from induced voltage.
Data transmission and railway signalling circuit effects.
Voice communication circuit effects.
Excitation of resonance conditions between the HVDC line and electrode
line.
Converter transformer DC currents in the neutral.
Harmonic impact on minimum current operation.
Bipolar and monopolar operation (with and without ground or metallic return).
During the harmonic measurement tests, the environmental conditions need to
be noted and recorded due to the sensitivity of the harmonic filters to ambient
temperature conditions or weather.
C o p y r i gh t e d m a t er i al l i c en s e d t oE l e c t r i c i t y of V i e t n am b y T h om s on S c i en t i f i c ,I n c
. ( www. t e c h s t r e e t . c om ) .T h i s c o p y d ownl o
a d e d on2 0 1 4 - 0 1 - 0 6 0 8 : 2 8 : 2 8 - 0 6 0 0 b y a u t h or i z e d u s er P h am V an c h i .
N of ur t h er r e pr o d u c t i on or d i s t r i b u t i oni s p er mi t t e d .
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– 86 – PAS 61975 © IEC:2004 (E)
Test Acceptance Criteria
The results of the performance measurements should verify that the AC and DC
harmonic voltages and currents are within the limits required and interference tothird party electrical systems is within acceptable limits. Additionally, the tests
should confirm that operating restrictions of the HVDC system and AC and DC
filter configurations are within specified limits. The AC and DC filter components
must not be overloaded.
5.2 Audible Noise
Introduction
HVDC systems emit noise in the audible-frequency spectrum. The source of the
audible noise (AN) in HVDC systems is from terminal equipment and HVDC
transmission lines and can be categorized as follows.
• Component generated audible noise:
Related to converter transformers, DC smoothing reactors, shunt reactors, AC and DC harmonic filter reactors and capacitors, thyristor valves, cooling
system, and auxiliary equipment. AN will vary with loading conditions and
firing angle changes.
• Conductor generated audible noise:
Related to corona phenomena on HVDC transmission lines, substation
buswork, and outdoor equipment. This source of AN is associated with
ionization phenomena near conductive surfaces when the electric fieldstrength is high enough to cause a breakdown of the surrounding air. As
such, corona generated AN can vary with environmental and ambient
conditions due to conductive surface irregularities and contamination. AN
from DC generated corona is usually higher under dry ambient conditions.
• Impact generated audible noise:
Related to operation of equipment such as power circuit breakers,
disconnect switches, etc.
C o p y r i gh t e d m a t er i al l i c en s e d t oE l e c t r i c i t y of V i e t n am b y T h om s on S c i en t i f i c ,I n c
. ( www. t e c h s t r e e t . c om ) .T h i s c o p y d ownl o
a d e d on2 0 1 4 - 0 1 - 0 6 0 8 : 2 8 : 2 8 - 0 6 0 0 b y a u t h or i z e d u s er P h am V an c h i .
N of ur t h er r e pr o d u c t i on or d i s t r i b u t i oni s p er mi t t e d .
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PAS 61975 © IEC:2004 (E) – 87 –
AN limits within the converter station facility, including building interiors, and
along the perimeter of the HVDC system are specified to ensure applicable
regulations and codes of practice are met. In some cases, special noise
abatement measures may be required to reduce the levels and spectrum of AN
from the HVDC system.
Test Objectives
The objectives of the AN tests are to measure and verify that the AN caused by
the HVDC system is within specified limits.
Preconditions
Before conducting AN tests the following preconditions must be fulfilled:
Defined locations for pre- and post-construction measurements.
Measurements available which establish preconstruction background levels
and spectrum of AN levels.
Study results available which estimate the levels and spectrum of AN fromthe HVDC system,
Factory AN test results available of applicable equipment
Test instrumentation and data acquisition system available.
Test Procedures
AN tests should be performed at predetermined locations in those HVDC system
configurations and modes of operation specified. A test plan which identifies
these configurations and physical locations for the AN measurements should be
established, considering the following HVDC system operating conditions:
Stand-by operation.
Minimum, intermediate, rated, and applicable overload HVDC power transfer
levels.
Any special condition generating maximum AN. Long term measurement considerations (when required).
C o p y r i gh t e d m a t er i al l i c en s e d t oE l e c t r i c i t y of V i e t n am b y T h om s on S c i en t i f i c ,I n c
. ( www. t e c h s t r e e t . c om ) .T h i s c o p y d ownl o
a d e d on2 0 1 4 - 0 1 - 0 6 0 8 : 2 8 : 2 8 - 0 6 0 0 b y a u t h or i z e d u s er P h am V an c h i .
N of ur t h er r e pr o d u c t i on or d i s t r i b u t i oni s p er mi t t e d .
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– 88 – PAS 61975 © IEC:2004 (E)
The presence of corona can create AN. Corona can be observed by visual
inspection with the use of binoculars or located with the use of ultra sonic corona
detection devices.
During the AN tests, the environmental conditions need to be noted and
recorded due to the sensitivity of AN measurements to ambient conditions, such
as air temperature, barometric pressure, relative humidity, wind speed and
direction, and background acoustic noise.
Instrumentation and AN measurement procedures should follow the specified
requirements or applicable standards.
Test Acceptance Criteria
Test criteria for AN levels resulting from HVDC systems are project specific and
depend to some degree on surrounding environments. The AN levels measured
with the HVDC system in operation must be within the design limits specified.
5.3 Overload/Temperature Rise
Introduction
HVDC systems may be designed and allowed to operate in an overload
condition where the HVDC power transfer level is greater than the rated value.
Overload operation may result in reduced performance of the HVDC system for
the following reasons:
Equipment life expectancy reduced due to increased thermal stresses.
Reduced reliability due to use of redundant equipment during overload
operation.
Limited ambient temperature operating range.
Restricted performance range for such critical operating parameters as
reactive power compensation and harmonic filter performance.
Control and instrumentation limits.
C o p y r i gh t e d m a t er i al l i c en s e d t oE l e c t r i c i t y of V i e t n am b y T h om s on S c i en t i f i c ,I n c
. ( www. t e c h s t r e e t . c om ) .T h i s c o p y d ownl o
a d e d on2 0 1 4 - 0 1 - 0 6 0 8 : 2 8 : 2 8 - 0 6 0 0 b y a u t h or i z e d u s er P h am V an c h i .
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Operating conditions and design requirements of the AC and HVDC system
should be able to support the overload operation without component damage.
Major equipment which can be directly affected by overload operation include
the thyristor valves, valve cooling system, converter transformers, harmonic
filters, smoothing reactor, current and voltage transformers, bushings, bus work,
and transmission systems.
Test Objectives
The objective of the overload/temperature rise tests are to verify the HVDC
systems overload performance capability and confirm the temperature rise of the
individual equipment is within acceptance limits.
Preconditions
Before conducting the tests the following preconditions shall be fulfilled.
Factory heat-run test results of major equipment available.
AC and DC transmission systems prepared for overload tests.
Temperature monitoring equipment inplace.
Ambient conditions are compatible with requirements.
Test Procedures
The HVDC system should be operated at rated load prior to commencement ofthe overload tests for a period of time necessary to achieve thermal equilibrium
of major electrical components such as converter transformers, DC smoothing
reactors, thyristor valves, AC and DC harmonic filters, and valve cooling system.
After the temperature of the major equipment items has thermally stabilized at
full load (typically 12-18 hours), the HVDC system can be operated under the
overload condition which is compatible with the existing ambient conditions and
the temperature rise of major electrical components recorded. In addition, the
valve cooling system performance should be monitored and temperature
C o p y r i gh t e d m a t er i al l i c en s e d t oE l e c t r i c i t y of V i e t n am b y T h om s on S c i en t i f i c ,I n c
. ( www. t e c h s t r e e t . c om ) .T h i s c o p y d ownl o
a d e d on2 0 1 4 - 0 1 - 0 6 0 8 : 2 8 : 2 8 - 0 6 0 0 b y a u t h or i z e d u s er P h am V an c h i .
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– 90 – PAS 61975 © IEC:2004 (E)
monitoring devices should be employed to check the buswork, connection
points, terminations, neutral connections, and switch contacts.
Test Acceptance Criteria
The maximum operating temperatures and temperature rise of the equipment
shall be within specified limits. The maximum operating temperature of
equipment being tested may have to be corrected to maximum ambient
temperature to compensate for lower ambient temperatures during test.
5.4 Interference
Introduction
HVDC systems produce voltages and currents in conductors which may cause
interference from both the conducted energy and radiated energy. Conductor
corona pulses and partial discharges on insulators are also potential sources of
electrical interference from HVDC systems.
Filtering devices, shielding, and noise suppression techniques are implemented
to minimize interference. Since electrical interference has the potential of
affecting third party electrical systems, the commissioning test program should
include coordinated tests with operators of interference-sensitive equipment-
Design criteria for interference levels resulting from HVDC systems are project
specific and depend on the surrounding environments and regulations.
Interference limits imposed typically consider the following:
Radio interference (Rl).
Television interference (TVI).
Telephone carrier interference (TCI).
Microwave communication system interference (MCSI),
Railroad signal interference (RSI),
Power line carrier interference (PLCI).
C o p y r i gh t e d m a t er i al l i c en s e d t oE l e c t r i c i t y of V i e t n am b y T h om s on S c i en t i f i c ,I n c
. ( www. t e c h s t r e e t . c om ) .T h i s c o p y d ownl o
a d e d on2 0 1 4 - 0 1 - 0 6 0 8 : 2 8 : 2 8 - 0 6 0 0 b y a u t h or i z e d u s er P h am V an c h i .
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Test Objectives
The objectives of the interference tests are to measure and verify that the inter-
ference levels caused by the HVDC system are within required limits andestablish that there is no degradation of low-level electric circuits (e.g. telephone
networks, computers, radio and television systems, railroad signal equipment,
and other electronic apparatus).
Preconditions
Before conducting interference tests the following preconditions shall be fulfilled.
Measurements available which establish pre-existing background
interference levels.
Study results available which estimate the levels of interference expected as
a result of HVDC system operations.
Coordination established with operators of interference-sensitive equipment.
HVDC system operating with all interference mitigating equipment in service.
HVDC station controls and protection verified to be immune from
interference.
Test instrumentation and data acquisition system available.
Test Procedures
Interference tests for the HVDC system can be broadly classified into the
following separate groups:
HVDC converter station tests with measurements taken within and adjacent
to the fenced boundary of the facilities.
Transmission line tests with measurements taken along a perimeter of the
AC and DC transmission lines servicing the HVDC system.
C o p y r i gh t e d m a t er i al l i c en s e d t oE l e c t r i c i t y of V i e t n am b y T h om s on S c i en t i f i c ,I n c
. ( www. t e c h s t r e e t . c om ) .T h i s c o p y d ownl o
a d e d on2 0 1 4 - 0 1 - 0 6 0 8 : 2 8 : 2 8 - 0 6 0 0 b y a u t h or i z e d u s er P h am V an c h i .
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The interference tests should be performed at predetermined locations and in
those HVDC system configurations and modes of operation specified. A test plan
which identifies these configurations and levels along with the physical locations
for the interference measurements should be established, considering the
following HVDC system operating conditions:
Stand-by operation,
Minimum, intermediate, rated and applicable overload HVDC power transfer
levels.
Any special condition generating maximum interference,
Number of points and number of measurements.
Test plan which identifies the bandwidths and measuring techniques,
correction factors, accuracy, antenna types, standards (where applicable),
frequency scans and spectrums, operating configurations and modes of the
HVDC system, ambient weather conditions, voltages, conductor
configuration, structure type and material),and elevation.
Test Acceptance Criteria
The interference levels measured with the HVDC system in operation must be within
the specified design limits and cause no degradation of low-level electric circuits.
5.5 Earth Electrode
Introduction
The earth electrodes for a bipole configured HVDC transmission system provide a
ground reference for the neutral bus at each converter station. The earth electrodes
are generally designed to permit the HVDC system to operate for a limited time
period in the monopolar ground return mode when one pole of the bipole is out of
service. Earth electrodes for monopole systems are designed to permit continuous
operation. Since earth return operation may interfere with third party communication
circuits and may cause corrosion of underground structures, the commissioning test
program should include coordination with third parties.
C o p y r i gh t e d m a t er i al l i c en s e d t oE l e c t r i c i t y of V i e t n am b y T h om s on S c i en t i f i c ,I n c
. ( www. t e c h s t r e e t . c om ) .T h i s c o p y d ownl o
a d e d on2 0 1 4 - 0 1 - 0 6 0 8 : 2 8 : 2 8 - 0 6 0 0 b y a u t h or i z e d u s er P h am V an c h i .
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Test Objectives
The objectives of the earth electrode test is to verify the design of the earth
electrodes and establish the maximum measured interference levels in various
operating modes. Design criteria for HVDC earth electrodes are project specific
and depend on the local soil conditions, anticipated operating modes, and
duration of earth return operation in the worst case scenario- Design criteria
typically considered include the following:
Current rating.
Temperature rise.
Thermal time constant.
Current distribution between electrode wells.
Current density at the electrode surface.
Earth resistivity design value.
Resistance of electrode to remote earth.
Electrode resistance.
Overload current capability.
Step and touch potential.
Preconditions
Before conducting the tests the following preconditions shall be fulfilled.
Earth electrode precommissioning tests including measurement of structure-
to-soil potential, current-in-structure, soil potential, soil resistivity, structure-
to-remote electrode-potential, and background interference level.
Test stations for cathodic protection and stray current measurements
established,
Coordination established with all participants, e.g., railroad operators,
telephone companies, municipalities, underground utility operators, electrode
supplier, and HVDC supplier.
Test coordination center and communication method established. Test instrumentation and data acquisition system available.
C o p y r i gh t e d m a t er i al l i c en s e d t oE l e c t r i c i t y of V i e t n am b y T h om s on S c i en t i f i c ,I n c
. ( www. t e c h s t r e e t . c om ) .T h i s c o p y d ownl o
a d e d on2 0 1 4 - 0 1 - 0 6 0 8 : 2 8 : 2 8 - 0 6 0 0 b y a u t h or i z e d u s er P h am V an c h i .
N of ur t h er r e pr o d u c t i on or d i s t r i b u t i oni s p er mi t t e d .
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Test Procedures
System tests for commissioning of the earth electrodes can be broadly classified
into the following separate groups:
low current tests with a direct current of 10-20 % of the rated direct current to
determine the basic earth electrode characteristics and identify the areas of
potential interference;
full rated tests of the earth electrodes with the direct current being increased
above the low current test level in incremental steps up to the full current
rating. Periodic cycling of the direct current and the magnitude of the direct
current incremental steps should be based upon a test schedule/plan.
Recording instruments need to be installed at all test points and areas of special
concern that are identified during the low current tests. The duration of the tests
at each direct current level must be appropriate for the thermal time constants of
concern and allow for the following test measurements to be taken.
Stray current magnitude caused by test current in affected structures.
Change in stray current flow caused by test current in affected structure. Change in potential caused by test current of structure-to soil.
Current distribution in each earth electrode well or electrode section.
Temperature rise versus test time to establish limits of full current test.
Induced voltage on communication circuits.
Stray currents in AC system transformer neutrals.
Structure-to-soil potential should be measured with the reference electrode
directly above buried structures or within one foot of above ground structures
such as railroads, and towers.
C o p y r i gh t e d m a t er i al l i c en s e d t oE l e c t r i c i t y of V i e t n am b y T h om s on S c i en t i f i c ,I n c
. ( www. t e c h s t r e e t . c om ) .T h i s c o p y d ownl o
a d e d on2 0 1 4 - 0 1 - 0 6 0 8 : 2 8 : 2 8 - 0 6 0 0 b y a u t h or i z e d u s er P h am V an c h i .
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Test Acceptance Criteria
The characteristics of the earth electrodes must be within the specified design
limits including temperature rise, voltage distribution, resistance, and uniformcurrent distribution among different electrode wells or electrode sections. The
results of the coordinated tests need to be analyzed and any unusual results
investigated and resolved between the affected parties.
C o p y r i gh t e d m a t er i al l i c en s e d t oE l e c t r i c i t y of V i e t n am b y T h om s on S c i en t i f i c ,I n c
. ( www. t e c h s t r e e t . c om ) .T h i s c o p y d ownl o
a d e d on2 0 1 4 - 0 1 - 0 6 0 8 : 2 8 : 2 8 - 0 6 0 0 b y a u t h or i z e d u s er P h am V an c h i .
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– 96 – PAS 61975 © IEC:2004 (E)
PART 6: OPERATION AND INTEGRATION TESTS
General
Introduction
In this part the operation and integration tests are described. These are the
system tests which seek to prove the response to change of configuration and
the transient behaviour of the AC and HVDC systems including recovery from
faults. Operation and integration tests are the final group of system tests before
the period of trial operation. Previous commissioning tests, including converter
tests and end to end tests have verified that the DC equipment being
commissioned functions correctly. The tests described are those recommended
only for two terminal and back to back HVDC systems. The following tests are
outlined:
6.1 Changes of DC configuration
6.2 Control performance6.3 Switching AC side filters and transformers
6.4 Loading tests
6.5 AC and DC system staged fault tests
6.6 Loss of telecommunications, auxiliaries, or redundant equipment
C o p y r i gh t e d m a t er i al l i c en s e d t oE l e c t r i c i t y of V i e t n am b y T h om s on S c i en t i f i c ,I n c
. ( www. t e c h s t r e e t . c om ) .T h i s c o p y d ownl o
a d e d on2 0 1 4 - 0 1 - 0 6 0 8 : 2 8 : 2 8 - 0 6 0 0 b y a u t h or i z e d u s er P h am V an c h i .
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Integration testing may also include all tests that would verify proper interaction
and coordination between the HVDC system under test and such other on-line
equipment as static VAR compensators, other HVDC systems, torsional
interactions, etc.
General Preconditions
The following activities shall have been completed before the operation and
integration tests can proceed:
- Off-site tests including AC/DC simulator tests
- Terminal tests including converter unit tests and converter station tests
- End-to-end tests to verify sequences and inter-station coordination
- Steady state operation including verification of steady state performance and
interference effects
Detailed procedures and plans should be prepared. As the tests may involve
some disturbance or increased risk to the connected AC systems, the operators
of the systems should be consulted-
The connected AC systems shall be within their specified range of parameters
and be capable to deliver the active and reactive power for the HVDC system re-
quired for the particular test/ Important parameters include.
AC voltage and frequency
Short circuit capacity
AC system configuration
Statement of Purpose
The purpose of the operation and integration tests is to verify the correct
operation of the HVDC system in combination with the associated AC systems,
within the limits given by the specification, under transient and change-over
conditions.
C o p y r i gh t e d m a t er i al l i c en s e d t oE l e c t r i c i t y of V i e t n am b y T h om s on S c i en t i f i c ,I n c
. ( www. t e c h s t r e e t . c om ) .T h i s c o p y d ownl o
a d e d on2 0 1 4 - 0 1 - 0 6 0 8 : 2 8 : 2 8 - 0 6 0 0 b y a u t h or i z e d u s er P h am V an c h i .
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General Test Objectives
Operation and integration tests are intended to verify the effects of changes in
DC main circuit configuration, control performance, switching and connection of
AC side equipment, AC and DC staged faults where required and the loss of
telecommunications and auxiliary functions.
6.1 Changes of DC Configuration
Introduction
Most HVDC long distance transmission schemes can be operated in several DCconfigurations such as monopolar earth electrode return, monopolar metallic
return, bipolar normal and in parallel operation. Each of these configurations can
contain one or more DC filters.
If series connected converter units per pole are used switching in and out of
these groups should be demonstrated. If the HVDC system uses polarity
reversal, this should be verified. Manoeuvres involving two or more terminals
can normally be performed with or without telecommunication.
Back-to-back stations do not require changes of DC configuration.
The test objectives, preconditions and test procedures are similar for the tests
under 6.1.1 through 6.1.3.
Regarding denomination of switches and their function refer to document CIGRE
WG 13/14.08: "Switching devices other than circuit breakers for HVDC systems",Part 1.
Test Objectives
Verify coordinated switching between converter terminals and for DC bus
reconfiguration and thus prevent switching conditions which can cause
severe stresses on the DC equipment.
C o p y r i gh t e d m a t er i al l i c en s e d t oE l e c t r i c i t y of V i e t n am b y T h om s on S c i en t i f i c ,I n c
. ( www. t e c h s t r e e t . c om ) .T h i s c o p y d ownl o
a d e d on2 0 1 4 - 0 1 - 0 6 0 8 : 2 8 : 2 8 - 0 6 0 0 b y a u t h or i z e d u s er P h am V an c h i .
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Switching of DC filters, if permitted, should not disturb the power flow of the
HVDG transmission more than specified.
Preconditions
Before conducting the tests the following preconditions must be fulfilled:
All sequences checked on the non-energized system
All AC and DC equipment energized
End-to-end tests completed
Test Procedures
During all tests AC and DC voltages and currents should be recorded. Outdoor
observations of sound and light phenomena should be made.
The timing of the various switching sequences should be verified. All switching
sequences should be performed step by step. If applicable, the sequences
should also be executed automatically. If two or more terminals are involvedtelecommunication will then be required.
Where appropriate, additional tests may be performed at lower than nominal
power and at minimum power.
Test Acceptance Criteria
The HVDC transmission should not be permanently disrupted by any change of
DC configuration. Currents and voltages should coincide with the results from
corresponding simulator tests and be in accordance with the specification.
C o p y r i gh t e d m a t er i al l i c en s e d t oE l e c t r i c i t y of V i e t n am b y T h om s on S c i en t i f i c ,I n c
. ( www. t e c h s t r e e t . c om ) .T h i s c o p y d ownl o
a d e d on2 0 1 4 - 0 1 - 0 6 0 8 : 2 8 : 2 8 - 0 6 0 0 b y a u t h or i z e d u s er P h am V an c h i .
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6.1.1 Tests from Monopolar Metallic Return Operation
From this configuration the following changes can be made:
- Connection and disconnection of DC filters- Transfer to monopolar earth electrode return
- Transfer to bipolar configuration
- Paralleling and deparalleling of another pole
Connection and disconnection of DC filters (if permitted):
- Record the DC filter harmonic current
- Operate at nominal power and disconnect one DC filter
- Connect the DC filter again
- Repeat the procedure for all DC filters
Additional test criteria:
- Rating of remaining filters should not be exceeded
- No burn marks should occur on the disconnects
Monopolar earth electrode return:
- Operate at nominal power
- Close the MRTB (Metallic Return Transfer Breaker)
- Open the GRTS (Ground Return Transfer Switch)
Bipolar operation:
- Operate at nominal power
- Close the MRTB
- Open the GRTS
- Close line pole disconnect of the non-operating pole
- Deblock non-operating pole
- Verify the current balance in both poles
C o p y r i gh t e d m a t er i al l i c en s e d t oE l e c t r i c i t y of V i e t n am b y T h om s on S c i en t i f i c ,I n c
. ( www. t e c h s t r e e t . c om ) .T h i s c o p y d ownl o
a d e d on2 0 1 4 - 0 1 - 0 6 0 8 : 2 8 : 2 8 - 0 6 0 0 b y a u t h or i z e d u s er P h am V an c h i .
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Paralleling/deparalleling:
- Operate one pole at nominal power
- Close paralleling disconnect of the non-operating pole
- Deblock the non-operating pole
- Verify the current balance in both poles
6.1.2 Tests from Monopolar Earth Return Mode
Monopolar earth return may only be allowed during a limited period of time. From
this configuration the following changes can be made:- Transfer to monopolar metallic return
- Transfer to bipolar operation
Transfer to monopolar metallic return:
- Operate at nominal power
- Close the GRTS
- Open the MRTB
Transfer to bipolar operation:
- Operate at nominal power
- Close the line pole disconnect of the non-operating pole
- Deblock the non-operating pole
- Verify the current balance in both poles
6.1.3 Tests from Bipolar Operation
From this specific configuration the following changes can be made:
- Connection/disconnection of DC filters
- Monopolar earth electrode return
- Monopolar metallic return
C o p y r i gh t e d m a t er i al l i c en s e d t oE l e c t r i c i t y of V i e t n am b y T h om s on S c i en t i f i c ,I n c
. ( www. t e c h s t r e e t . c om ) .T h i s c o p y d ownl o
a d e d on2 0 1 4 - 0 1 - 0 6 0 8 : 2 8 : 2 8 - 0 6 0 0 b y a u t h or i z e d u s er P h am V an c h i .
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Connection and disconnection of DC filters (if permitted):
- Record the DC filter harmonic current
- Operate at nominal power and disconnect one DC filter
- Connect the DC filter again
- Repeat the procedure for all DC filters
Additional test criteria:
- Rating of remaining filters should not be exceeded
- No burn marks should occur on the disconnects
- No adverse transient effects
Monopolar earth electrode return:
- Operate up to maximum specified power, for monopolar operation
- Reduce the current in one pole to a minimum but keep the bipole power
constant
- Block the pole with minimum power
- Open the line pole disconnect in the blocked pole
Monopolar metallic return:
- Operate up to maximum specified power
- Reduce the current in one pole to a minimum but keep the bipole power
constant
- Block the pole with minimum power
- Open the line pole disconnect in the blocked pole
- Close the GRTB
- Open the MRTB
C o p y r i gh t e d m a t er i al l i c en s e d t oE l e c t r i c i t y of V i e t n am b y T h om s on S c i en t i f i c ,I n c
. ( www. t e c h s t r e e t . c om ) .T h i s c o p y d ownl o
a d e d on2 0 1 4 - 0 1 - 0 6 0 8 : 2 8 : 2 8 - 0 6 0 0 b y a u t h or i z e d u s er P h am V an c h i .
N of ur t h er r e pr o d u c t i on or d i s t r i b u t i oni s p er mi t t e d .
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6.2 Control Performance General
In HVDC systems various control loops are utilized. This chapter describes the
recommended system tests to prove the steady state and dynamic performanceof the control system.
Test Objectives
The site tests are performed to fine-tune the response of each control loop
following a change in the reference value and to verify the control behaviour
during disturbances causing changes in the actual measured quantities (DCcurrent, DC voltage etc.) of the respective control loop.
The tests are designed to verify that the controllers will not interfere with each
other or cause disturbances to the AC and/or DC systems. Controllers
insensitivity to AC system disturbances should also be verified. The following
sections will describe the tests necessary for control performance verification
under:
- Step response
- Control mode transfer
- AC system interaction / control
- Commutation failure
Preconditions
Before conducting all the tests the following preconditions must be completed:
- Off-site testing of the control system
- Converter unit tests
- Start/stop sequences checked
- Protection sequences checked
- Communication system operational
C o p y r i gh t e d m a t er i al l i c en s e d t oE l e c t r i c i t y of V i e t n am b y T h om s on S c i en t i f i c ,I n c
. ( www. t e c h s t r e e t . c om ) .T h i s c o p y d ownl o
a d e d on2 0 1 4 - 0 1 - 0 6 0 8 : 2 8 : 2 8 - 0 6 0 0 b y a u t h or i z e d u s er P h am V an c h i .
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– 104 – PAS 61975 © IEC:2004 (E)
All the equipment from the DC system necessary for power transmission of one
pole must be available. The AC systems should be set up as close as possible to
the minimum design effective short circuit ratio.
Test Procedures
The procedure for each test will be described in each section separately. All
tests for optimization and verification of the control performance require a similar
recording and monitoring set-up. This monitoring and recording set-up is listed
below. In cases where additional or different set-ups are required this is outlined
in the individual sections. The control performance tests would have been
performed during the off-site tests and can be used as a reference for all site
tests. It is also recommended to use the same recording equipment, monitored
signals and test report sheets as were used during the off-site tests. The
variables which should be monitored, include:
- Current order fat the current controller input)
- Actual DC current (at the current controller)
- Output of current controller
- DC voltage
- Extinction angle at the extinction angle controller
- Output of extinction angle controller
- Final control voltage to tiring controls (alpha order)
- Identification of active controller
- AC busbar voltage (3 phases)
- DC power
- Force retard command
- Stabilizing (damping) control signals (if any)
C o p y r i gh t e d m a t er i al l i c en s e d t oE l e c t r i c i t y of V i e t n am b y T h om s on S c i en t i f i c ,I n c
. ( www. t e c h s t r e e t . c om ) .T h i s c o p y d ownl o
a d e d on2 0 1 4 - 0 1 - 0 6 0 8 : 2 8 : 2 8 - 0 6 0 0 b y a u t h or i z e d u s er P h am V an c h i .
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6.2.1 Step Response Introduction
This type of test will depend on the various control modes in the HVDC system.
There are different modes of operation for each terminal of an HVDC system.
The most common ones are:
- Constant current control
- Constant minimum extinction angle control
- Constant DC voltage control
- Current error control
- Constant power control
Some of these control modes are only valid for operation as a rectifier or an
inverter.
Based on the large variety of possible HVDC system controls it is difficult to
design one test to cover all possible control scenarios. Thus the tests will be
described for the most common control loops.
If we consider the case of an HVDC system where the rectifier is in constant
current control and the inverter is in constant minimum extinction angle control,
then the controllers to be optimized in this case are:
- Rectifier current controller
- Inverter extinction angle controller
- Inverter current controller (margin current control)
- Rectifier extinction angle controller- Constant power controller
- Voltage dependant current order limiter (VDCOL)
Test Objectives
The objective of a step response test is to optimize the individual controller
which is active in a specific mode of operation to achieve stability.
C o p y r i gh t e d m a t er i al l i c en s e d t oE l e c t r i c i t y of V i e t n am b y T h om s on S c i en t i f i c ,I n c
. ( www. t e c h s t r e e t . c om ) .T h i s c o p y d ownl o
a d e d on2 0 1 4 - 0 1 - 0 6 0 8 : 2 8 : 2 8 - 0 6 0 0 b y a u t h or i z e d u s er P h am V an c h i .
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Preconditions
Before conducting step response tests the following preconditions shall be
completed:- Off-site testing of the control system
- Converter unit tests
- Start/stop sequences
- Protection sequences
- Communication system
Test Procedures
It has proved to be good practice to implement the control settings obtained from
the off-site tests on the simulator and then fine tune them during the step
response tests with the real HVDC system.
Step response tests are performed at all controllers beginning at the converter
level and continuing toward station and system level.
C o p y r i gh t e d m a t er i al l i c en s e d t oE l e c t r i c i t y of V i e t n am b y T h om s on S c i en t i f i c ,I n c
. ( www. t e c h s t r e e t . c om ) .T h i s c o p y d ownl o
a d e d on2 0 1 4 - 0 1 - 0 6 0 8 : 2 8 : 2 8 - 0 6 0 0 b y a u t h or i z e d u s er P h am V an c h i .
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Rectifier Current Controller
Several methods can be used to fine tune the current controller at the rectifier The
typical one is to apply a step change in the current order. The duration of theapplied step (T) should be long enough to allow the system to stabilize following
the change in current order. The level of the current order (lo) prior to the step
change should be chosen keeping in mind that during the application of a step-up
in the current order (I) no limits are encountered. The location of application of
the current order step should be as close as possible to the input of the current
controller. During the test the rectifier must always be in DC current control and
the current controller at the inverter should be prevented from interfering.
Inverter Extinction Angle Controller
In order to optimize this controller at the inverter the rectifier will be in its normal
mode of control and the inverter should be in the minimum constant extinction
angle control- A step change in the extinction angle reference at the controller
should be applied. The first step change, A) should be applied only in the
direction of increasing the reference to avoid commutation failures. The
magnitude of the step () should be such that reaching any extinction angle
limits is avoided.
After optimization of the controller parameters a second step change B) from
o + back to o should be applied.
C o p y r i gh t e d m a t er i al l i c en s e d t oE l e c t r i c i t y of V i e t n am b y T h om s on S c i en t i f i c ,I n c
. ( www. t e c h s t r e e t . c om ) .T h i s c o p y d ownl o
a d e d on2 0 1 4 - 0 1 - 0 6 0 8 : 2 8 : 2 8 - 0 6 0 0 b y a u t h or i z e d u s er P h am V an c h i .
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– 108 – PAS 61975 © IEC:2004 (E)
It should be noted that in the case where the controller has other inputs, whichwill affect the extinction angle, the process should also be repeated for these
inputs. For example if there is an input that will increase the extinction angle due
to a sudden increase in DC current or a sudden decrease in the AC voltage, then
these functions should be checked following the optimization with step changes
in the extinction angle.
Inverter Current Controller (Margin Current Controller)
During this test the rectifier has to be In constant firing angle control (alpha
minimum) and the inverter is in constant current mode of operation. A step
change in the current order at the input of the inverter current controller is
applied. The duration of the step (T) is long enough to achieve stable operation
following its application. Before applying the step, the magnitude of current (lo) is
such that no current order limits are encountered when a step l is applied.
C o p y r i gh t e d m a t er i al l i c en s e d t oE l e c t r i c i t y of V i e t n am b y T h om s on S c i en t i f i c ,I n c
. ( www. t e c h s t r e e t . c om ) .T h i s c o p y d ownl o
a d e d on2 0 1 4 - 0 1 - 0 6 0 8 : 2 8 : 2 8 - 0 6 0 0 b y a u t h or i z e d u s er P h am V an c h i .
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Rectifier Extinction Angle Controller
In order to fine tune the extinction angle controller at the rectifier, two situations
can be considered.
1. In the case of a transmission system where the direction of power is
always constant. One terminal is always a rectifier and the other is
always an inverter. Then the function of this controller will be limited to
the situation when force retard is applied. The response of the controller
should be checked during the application of force retard.
2. In the case of an HVDC system where power reversal is used the
optimization of the controller at the second terminal should be performed
during transmission in the reverse power direction.
Constant Power Controller
In order to optimize this controller a step change in the power order (P) is
applied. The duration of the applied step (T) should be long enough to allow
stable operation to be achieved. The level of the power order (P o) prior to the
step change should be chosen, keeping in mind that during the application of a
step up in power order P no limits are encountered. The step size of P should
be chosen such that the change in current order exceeds the current margin.
Additional tests with smaller P may be conducted to check for instability and
interaction with other control loops.
C o p y r i gh t e d m a t er i al l i c en s e d t oE l e c t r i c i t y of V i e t n am b y T h om s on S c i en t i f i c ,I n c
. ( www. t e c h s t r e e t . c om ) .T h i s c o p y d ownl o
a d e d on2 0 1 4 - 0 1 - 0 6 0 8 : 2 8 : 2 8 - 0 6 0 0 b y a u t h or i z e d u s er P h am V an c h i .
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– 110 – PAS 61975 © IEC:2004 (E)
Test Acceptance Criteria
All controller settings must be adjusted such that recovery times and design
criteria as determined in system studies and requested by the specifications are
not exceeded.
All control system parameters shall be similar to those obtained during the off-
site tests. Deviations between the real DC system and the off-site tests can
occur, but must be explained.
Optimization shall be such that the response of the DC system to the step
change will be in a manner that shows the least amount of overshoot and the
shortest settling time.
No instability shall occur during the step response tests.
6.2.2 Control Mode Transfer
Introduction
The basic control mode transfer can be divided into two general types:
- From constant power control mode to constant current control mode and
back.
- From constant extinction angle control mode or constant DC voltage control
mode to constant current control mode and back at the inverter.
Additional control modes may be applied for special applications. Their control
mode transfer needs to be tested with respect to the particular application. The
test criteria, however, are anticipated to be similar as for the basic control mode
transfer as discussed here after.
HVDC systems are typically operated in constant power order control mode.
Under certain conditions it will be necessary to transfer from constant power
control mode to constant current order control mode. At the pole control level it
is a typical configuration to operate the rectifier in constant current control and
the inverter in constant extinction angle control.
C o p y r i gh t e d m a t er i al l i c en s e d t oE l e c t r i c i t y of V i e t n am b y T h om s on S c i en t i f i c ,I n c
. ( www. t e c h s t r e e t . c om ) .T h i s c o p y d ownl o
a d e d on2 0 1 4 - 0 1 - 0 6 0 8 : 2 8 : 2 8 - 0 6 0 0 b y a u t h or i z e d u s er P h am V an c h i .
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It is common practice to have the inverter also equipped with a constant current
controller. During certain AC system conditions a transfer from constant
extinction angle control mode to constant current control mode and back will be
required at the inverter.
Test Objectives
Control mode transfer tests are performed to verify that the HVDC control
system will transfer from one control mode to another smoothly and without any
adverse effect on the power system.
Preconditions
Before conducting control mode transfer tests the following preconditions shall
be completed:
- Off-site testing of the control system
- Converter unit tests
- Start/stop sequences
- Protection sequences
- Communication system
The step response tests will have been completed and the individual controllers
are optimized.
Test Procedures
For DC systems where the transfer from constant power order control mode to
constant current order control mode is a manual function, the DC system will be
started in constant power order control mode. The transfer to constant current
order control mode must only take place when the actual DC current and the
new DC current reference value match. The matching can be performed
manually or automatically.
C o p y r i gh t e d m a t er i al l i c en s e d t oE l e c t r i c i t y of V i e t n am b y T h om s on S c i en t i f i c ,I n c
. ( www. t e c h s t r e e t . c om ) .T h i s c o p y d ownl o
a d e d on2 0 1 4 - 0 1 - 0 6 0 8 : 2 8 : 2 8 - 0 6 0 0 b y a u t h or i z e d u s er P h am V an c h i .
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– 112 – PAS 61975 © IEC:2004 (E)
In some cases the transfer from constant power order control mode to constant
current order control mode is also activated automatically during any decline in
the AC bus voltage, in order to avoid power/voltage instability. If such a feature
is available this control mode transfer shall be checked. This can be performed
by simulating AC undervoltage or during AC system faults.
The control mode transfer from constant extinction angle control to constant
current control at the inverter can be checked by operating the rectifier at its
minimum firing angle and forcing the inverter into current control- A typical
means to perform this test is through the use of tap changer operations.
This test can be performed in constant current order control mode or in constant
power order control mode.
Test Acceptance Criteria
The control mode transfer is expected to be a smooth transition with stable
operation during and after the transfer from constant power control to constant
current control and back.
Step changes in power shall not occur during the control mode transfer.
The control mode transfer from constant extinction angle control to constant
current control at the inverter shall be stable.
C o p y r i gh t e d m a t er i al l i c en s e d t oE l e c t r i c i t y of V i e t n am b y T h om s on S c i en t i f i c ,I n c
. ( www. t e c h s t r e e t . c om ) .T h i s c o p y d ownl o
a d e d on2 0 1 4 - 0 1 - 0 6 0 8 : 2 8 : 2 8 - 0 6 0 0 b y a u t h or i z e d u s er P h am V an c h i .
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6.2.3 AC System Interaction / Control Introduction
The controllability of HVDC systems is an important advantage of this
technology. Additional DC controls also make it possible to operate HVDCsystems with weak AC systems. This feature can be valuable in improving the
dynamic performance of large AC systems.
To achieve these advantages, the control systems must perform appropriately
for various disturbances and system conditions. The control loops shall not
interact unfavourably with each other.
To obtain adequate control performance, operation at higher than nominalrectifier firing angles or higher than minimum inverter extinction angles may be
required.
Commonly specified AC system interaction/control functions are:
- Frequency control
- Reactive power regulation
- AC voltage control
- Temporary overvoltage control
- Damping of frequency or power oscillations
- Frequency or power dependent power changes
- Special controls during faults
Test Objectives
The objectives are to optimize the individual controller active in a specific mode
of operation to achieve stability with the actual HVDC transmission system.
C o p y r i gh t e d m a t er i al l i c en s e d t oE l e c t r i c i t y of V i e t n am b y T h om s on S c i en t i f i c ,I n c
. ( www. t e c h s t r e e t . c om ) .T h i s c o p y d ownl o
a d e d on2 0 1 4 - 0 1 - 0 6 0 8 : 2 8 : 2 8 - 0 6 0 0 b y a u t h or i z e d u s er P h am V an c h i .
N of ur t h er r e pr o d u c t i on or d i s t r i b u t i oni s p er mi t t e d .
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Preconditions
Before conducting the tests of AC system/interaction control functions the
following shall be completed:- Off-site testing of the control system
- Converter unit tests
- Start/stop sequences checked
- Protection sequences checked
- Communication system operational
The step response tests will have been completed and the individual controlloops are optimized.
AN control mode transfer tests shall have been completed. The AC system
should be set up in a condition which refers to the specific AC system
interaction/controller.
Test Procedures
The test procedures for the AC system interaction controllers may differ for the
individual application and functions.
Where applicable it has proved to be good practice to implement the control
settings obtained from off site tests on the simulator and then fine tune them to
the real HVDC system.
Testing the control behaviour during disturbances shall be planned very
carefully. The execution involves the connected AC system and can have a
serious impact on it.
C o p y r i gh t e d m a t er i al l i c en s e d t oE l e c t r i c i t y of V i e t n am b y T h om s on S c i en t i f i c ,I n c
. ( www. t e c h s t r e e t . c om ) .T h i s c o p y d ownl o
a d e d on2 0 1 4 - 0 1 - 0 6 0 8 : 2 8 : 2 8 - 0 6 0 0 b y a u t h or i z e d u s er P h am V an c h i .
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PAS 61975 © IEC:2004 (E) – 115 –
AC system disturbances or HVDC operating mode changes to check the
interaction of the HVDC system with the AC system may be initiated by:
- Load rejection (simulated DC line faults)
- AC line switching
- Generator tripping
- Ramping of DC power
- Power reversal
- Transformer energizing
- Filter switching
- AC or DC line faults
- Modulation of generator excitation system
Some of the above mentioned initiating functions are also dealt with in 6.3
and 6.5.
Test Acceptance Criteria
All controller settings must be adjusted such that recovery times and design
criteria as determined in system studies and requested by the specifications are
not exceeded.
All control system parameters shall be similar to those obtained during the off-
site tests. Deviations between the results from site tests and the results from off-
site tests can occur, but shall be explained.
No instability shall occur during the AC interaction/control tests.
-
C o p y r i gh t e d m a t er i al l i c en s e d t oE l e c t r i c i t y of V i e t n am b y T h om s on S c i en t i f i c ,I n c
. ( www. t e c h s t r e e t . c om ) .T h i s c o p y d ownl o
a d e d on2 0 1 4 - 0 1 - 0 6 0 8 : 2 8 : 2 8 - 0 6 0 0 b y a u t h or i z e d u s er P h am V an c h i .
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– 116 – PAS 61975 © IEC:2004 (E)
6.2.4 Commutation Failures Introduction
Commutation failures on a DC system can be caused by either:
- AC system disturbances- Converter control malfunction
Commutation failures may occur only once (single commutation failure), or
during a number of consecutive periods (multiple commutation failure), or may
be persistent (persistent commutation failure). Commutation failures by
converter control malfunction will be simulated during the tests described in this
part. Trial operation provides a useful further test with regard to normal system
disturbances (rather than those simulated).
Test Objectives
To observe and confirm that the control system is stable during and after
commutation failures and valve misfires, and that recovery is achieved within the
prescribed time period.
In the case of a DC system where the DC power circuit is resonant at a
frequency close to the fundamental, the commutation failures may excite
oscillations on the DC side. The tests will demonstrate that the control system
will be able to damp such oscillation upon the removal of the excitation. In
addition the tests will demonstrate that these oscillations will not be magnified
due to the action of the control system.
To check the commutation failure protection and any valve overload protection
such as voltage dependent current limits.
In the case of HVDC systems with overhead lines or cables, the tests are
designed to ensure that the DC line or cable protection will not operate during
these disturbances.
C o p y r i gh t e d m a t er i al l i c en s e d t oE l e c t r i c i t y of V i e t n am b y T h om s on S c i en t i f i c ,I n c
. ( www. t e c h s t r e e t . c om ) .T h i s c o p y d ownl o
a d e d on2 0 1 4 - 0 1 - 0 6 0 8 : 2 8 : 2 8 - 0 6 0 0 b y a u t h or i z e d u s er P h am V an c h i .
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Preconditions
Before conducting commutation failure tests, the optimization of the control
system must be completed.
All equipment from the DC system for one pole necessary for power
transmission must be available.
In the case of long-distance transmission, the DC line or cable protection should
be with its final settings.
The telecommunications should be available in the case of long-distance
transmission.
The inverter AC system should be set up as close as possible to the minimum
design effective short-circuit ratio.
Test Procedures
The tests are described for one direction of power flow and should be repeated ifthe system is designed for power reversal.
The tests may be carried out at several current levels up to rated current,
In the case of long-distance transmission and series connected groups per pole,
the tests shall be performed for all groups in operation and, if permitted by the
plant design, also with reduced numbers of groups.
In addition to the monitoring points listed in the general section the following
signals will be monitored during the tests:
- The measured firing angle
- The firing pulses to the valves
C o p y r i gh t e d m a t er i al l i c en s e d t oE l e c t r i c i t y of V i e t n am b y T h om s on S c i en t i f i c ,I n c
. ( www. t e c h s t r e e t . c om ) .T h i s c o p y d ownl o
a d e d on2 0 1 4 - 0 1 - 0 6 0 8 : 2 8 : 2 8 - 0 6 0 0 b y a u t h or i z e d u s er P h am V an c h i .
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These monitoring points may vary from one system to another.
The valve commutation failure in inverter operation or a firing failure in rectifier
operation will be achieved by blocking the firing pulses to one valve. Cautionshould be observed that sometimes the block of one firing pulse in the control
system may initiate certain actions in the control and protection, which will create
abnormal situations, hence the location of blocking the pulse should be
considered carefully, depending on the particular valve design.
The duration of the applied commutation failure or firing failure respectively shall
be increased in steps:
- Duration shorter than the time required to initiate any protective action
- Duration long enough to activate any valve overload protection such as
voltage dependent current limiting
- Duration long enough to initiate the persistent commutation failure or firing
failure protection (tripping of the converter)
In the case of long-distance transmission this test should be performed with and
without telecommunications.
Test Acceptance Criteria
The test criteria depends on the duration of the commutation failure and the
respective station of the selective protection system.
- No protection system initiated:
The controls shall perform reliably and recover within the specified time. Any
oscillations must be damped.
- Initiation of valve overload protection:
The DC current shall be reduced by control action and the system should
recover following the end of the commutation failures.
C o p y r i gh t e d m a t er i al l i c en s e d t oE l e c t r i c i t y of V i e t n am b y T h om s on S c i en t i f i c ,I n c
. ( www. t e c h s t r e e t . c om ) .T h i s c o p y d ownl o
a d e d on2 0 1 4 - 0 1 - 0 6 0 8 : 2 8 : 2 8 - 0 6 0 0 b y a u t h or i z e d u s er P h am V an c h i .
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- Initiation of the persistent commutation failure protection:
The designed sequence of tripping the converter should be verified. DC
system and AC system components must not be affected.
6.3 Switching AC Filters and Transformers Introduction
The switching of AC system components such as AC filters and transformers can
create disturbances to the AC system. These disturbances are due to inrush
current, saturation of components as well as resonance conditions.
Test Objectives
The objectives are to confirm that switching will not have any adverse effect on
the operation of the DC system and that AC system voltage disturbances are
within the prescribed limits. Proper recovery from commutation failures, if any,
should be verified.
The HVDC control system should perform without instability during suchconditions and in cases where it is used to produce a damping effect to such
disturbances, its performance should be verified.
Preconditions
All control performance tests under 6.2 should have been performed.
The commutation failure protection is functional.
All AC and DC equipment for the pole under test are available.
C o p y r i gh t e d m a t er i al l i c en s e d t oE l e c t r i c i t y of V i e t n am b y T h om s on S c i en t i f i c ,I n c
. ( www. t e c h s t r e e t . c om ) .T h i s c o p y d ownl o
a d e d on2 0 1 4 - 0 1 - 0 6 0 8 : 2 8 : 2 8 - 0 6 0 0 b y a u t h or i z e d u s er P h am V an c h i .
N of ur t h er r e pr o d u c t i on or d i s t r i b u t i oni s p er mi t t e d .
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Test Procedures
The tests should be performed in those configurations with those levels of the
DC current per pole and the inverter and rectifier AC systems and with thoseswitching instants which according to system studies tend to produce the most
onerous over-voltage or resonance conditions.
The tests will vary depending on the HVDC system configuration, for example:
Bipolar or monopolar systems
Groups in series or single groups per pole (long-distance transmission)
Back-to-back systems
If the DC system is bipolar and with a single group per pole whether back-to-
back or long-distance, then the test should be performed by switching on and off
the converter transformer in one pole while the other pole is in operation. This
means that the test can be performed only in monopolar operation, unless there
is a transformer bank on site or close to the DC terminal of comparable rating
that can be switched on and off after suitable time intervals. The same testshould also be repeated for switching each type of AC filter. In some systems
where redundant AC filters are available this test can be performed in bipolar
operation.
If the DC system is bipolar with more than one valve group in series per pole
(long-distance transmission), the test should be performed by switching on and
off one converter transformer while the system is in bipolar operation, provided
that the plant design permits unbalanced numbers of groups per pole. The sametest can also be repeated for the switching of an AC filter.
The tests should be performed at both the rectifier and inverter stations.
C o p y r i gh t e d m a t er i al l i c en s e d t oE l e c t r i c i t y of V i e t n am b y T h om s on S c i en t i f i c ,I n c
. ( www. t e c h s t r e e t . c om ) .T h i s c o p y d ownl o
a d e d on2 0 1 4 - 0 1 - 0 6 0 8 : 2 8 : 2 8 - 0 6 0 0 b y a u t h or i z e d u s er P h am V an c h i .
N of ur t h er r e pr o d u c t i on or d i s t r i b u t i oni s p er mi t t e d .
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The monitoring includes:
- DC current
- DC voltage
- DC power
- AC system voltage - 3 phases
- AC filter currents
- Transformer primary currents
- Extinction angle
Test Acceptance Criteria
In all the switching tests the HVDC system should recover to stable operation.
Commutation failures may occur during the test. AC system overvoltages may
occur but must remain within the specified limits.
6.4 Loading Tests
Introduction
All components in an HVDC system are designed for a certain permissible
operating temperature. They are either cooled naturally or require forced cooling.
Special cooling systems are required for the main components like valves, trans-
formers and smoothing reactors. For availability reasons most of the cooling
systems have redundancy. The loading tests should include a complete
performance test of the cooling systems.
Overload capabilities depend on the loading capability of the main components
and the ambient temperature.
Loading tests are also known as heat run tests.
If any additional loss tests to those performed in the factory have been specified,
they may be performed during the loading tests.
C o p y r i gh t e d m a t er i al l i c en s e d t oE l e c t r i c i t y of V i e t n am b y T h om s on S c i en t i f i c ,I n c
. ( www. t e c h s t r e e t . c om ) .T h i s c o p y d ownl o
a d e d on2 0 1 4 - 0 1 - 0 6 0 8 : 2 8 : 2 8 - 0 6 0 0 b y a u t h or i z e d u s er P h am V an c h i .
N of ur t h er r e pr o d u c t i on or d i s t r i b u t i oni s p er mi t t e d .
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Test Objectives
The general test objectives are to verify the proper function of all cooling
systems with respect to cooling controls and redundancy requirements and toverify the loading capability within specified temperatures of all major HVDC
system components and the total system under rated load conditions and, as far
as possible, at overload conditions.
Preconditions
To perform loading tests the relevant part of the HVOC system must be ready foroperation.
The AC systems must be available for power transfer at levels as required for
the loading test.
The ambient temperatures should ideally be close to the maximum design
temperature. For testing maximum overload conditions ambient temperatures
should be as low as possible.
Test Procedures
The HVDC system has to be operated in a mode of operation allowing the HVDC
components to reach their maximum operating temperature. In most cases this
will be achieved at the maximum current level, at maximum ambient temperature
and with the cooling system redundancy not in use.
In some applications the HVDC components will have their maximum loading
and operating temperature at a different mode of operation than the maximum
current level (e.g. with firing angles close to 90 degrees electrical).
C o p y r i gh t e d m a t er i al l i c en s e d t oE l e c t r i c i t y of V i e t n am b y T h om s on S c i en t i f i c ,I n c
. ( www. t e c h s t r e e t . c om ) .T h i s c o p y d ownl o
a d e d on2 0 1 4 - 0 1 - 0 6 0 8 : 2 8 : 2 8 - 0 6 0 0 b y a u t h or i z e d u s er P h am V an c h i .
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The loading test must be performed with ample duration to ensure that all
components will have reached a steady state operating temperature. If maximum
ambient temperature is not available, the tests shall be performed at the existing
ambient temperature and the anticipated component temperatures at maximum
ambient temperature shall be calculated from design load curves.
The temperatures are monitored by means of temperature indicators or by
infrared scanning. Ambient temperature, room temperatures and cooling circuit
temperature will be recorded- All equipment is monitored by visual inspection.
For overload conditions the cooling systems may be operated with ail available
redundancy. Ambient conditions may support the cooling capacity.
After the loading tests are finished gas in oil analysis may be performed for the
major oil filled components.
Test Acceptance Criteria
Neither under normal operating conditions or under overload conditions shall
design temperature rise of any HVDC component be exceeded.
No hotspots should occur in the buswork and the connectors.
The cooling control shall control the cooling systems to dissipate all heat losses
specified ambient conditions
The power capability shall be in accordance with the specified loading curve.
Proper function of the various cooling control circuits and the redundancy
requirements should be verified.
C o p y r i gh t e d m a t er i al l i c en s e d t oE l e c t r i c i t y of V i e t n am b y T h om s on S c i en t i f i c ,I n c
. ( www. t e c h s t r e e t . c om ) .T h i s c o p y d ownl o
a d e d on2 0 1 4 - 0 1 - 0 6 0 8 : 2 8 : 2 8 - 0 6 0 0 b y a u t h or i z e d u s er P h am V an c h i .
N of ur t h er r e pr o d u c t i on or d i s t r i b u t i oni s p er mi t t e d .
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6.5 AC and DC System Staged Faults Introduction
The reaction of an HVDC system with the connected AC networks must be
known precisely in case of AC network faults so that appropriate control actionscan be applied. Normally, to maintain stability, the DC power flow shall be re-
established without undue delay when commutating voltages reappear after fault
clearance. Due to inrush currents the voltages may be severely distorted. This
may complicate the tasks of the control system and circulate unconventional
current waveforms in the protection relays of the AC system with the associated
risk of spurious protection operation.
The use of staged fault-testing to verify proper function of the HVDC system may
be a controversial issue. Verification by utilizing simulation or digital study tools
could be an alternative. If staged fault tests are conducted, they may require the
arrangement of particular system conditions which may imply high cost and
expose the affected equipment to high stress which may effect equipment life
time. However, since faults to the AC and DC systems are most likely to occur
during the life of a project, some power utilities recognize the merits of staged
fault testing to verify the AC and DC system protection and survivability.
Modern digital study and simulation tools are considered to be adequate and
precise and some utilities prefer to rely on such tools or HVDC simulators in
preference to performing staged fault tests. In such cases it will also be required
to verify the proper function and coordination of the control and protection
equipment. It should be also verified that the stress on all components in the AC
and DC system will not exceed their permissible limits. This pertains particularly
to the AC system faults.
Transient faults on the DC line are normally cleared by the combined action of
protection and converter control, which extinguishes the arc by temporary
blocking, or by force retarding the rectifier.
C o p y r i gh t e d m a t er i al l i c en s e d t oE l e c t r i c i t y of V i e t n am b y T h om s on S c i en t i f i c ,I n c
. ( www. t e c h s t r e e t . c om ) .T h i s c o p y d ownl o
a d e d on2 0 1 4 - 0 1 - 0 6 0 8 : 2 8 : 2 8 - 0 6 0 0 b y a u t h or i z e d u s er P h am V an c h i .
N of ur t h er r e pr o d u c t i on or d i s t r i b u t i oni s p er mi t t e d .
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In case of permanent fault on the DC side, depending on the design of the DC
line, an automatic sequence must localize the faulted section, isolate it and re-
establish if possible the initial power flow as rapidly as possible. Consequences
of DC system faults on the AC systems are generally less severe than those due
to AC system faults.
Test Objectives
The objective of these tests is to verify the ability of the combined AC/DC system
to react as specified during and immediately after fault clearance.
In case of AC system distant faults, that means the converters must continue to
operate without commutation failure or with a specified maximum number of
commutation failures. In case of close faults, the DC power flow must be re-
established within a specified time after fault clearance. In case of DC side
faults, the rated DC power, if possible (depending on the HVDC design), must be
re-established within specified time after clearance of the fault.
Preconditions
The following preconditions shall be fulfilled.
- All AC and DC equipment energized
- End-to-end tests completed
- Changes of DC configuration (6.1) completed
- Response of protection relays in the AC system checked with distortedwaveforms
- Control and protection performance tests (6.2) completed
- Switching of AC filters and transformers (6.3) completed)
C o p y r i gh t e d m a t er i al l i c en s e d t oE l e c t r i c i t y of V i e t n am b y T h om s on S c i en t i f i c ,I n c
. ( www. t e c h s t r e e t . c om ) .T h i s c o p y d ownl o
a d e d on2 0 1 4 - 0 1 - 0 6 0 8 : 2 8 : 2 8 - 0 6 0 0 b y a u t h or i z e d u s er P h am V an c h i .
N of ur t h er r e pr o d u c t i on or d i s t r i b u t i oni s p er mi t t e d .
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– 126 – PAS 61975 © IEC:2004 (E)
Test Procedures
For any type of staged fault the following pre-fault system conditions must be
specified and post-fault conditions estimated:- Telecommunication on or off
- Frequency of the AC systems (in case of an isolated system)
- AC system voltage before and after the fault
- Configuration of the AC system where staged faults are applied, before and
after the fault (lines in service to the nearest substations, close-by
generating units, loads)
- Short-circuit levels on both sides of the DC link
- Initial DC power flow
- HVDC system configuration including AC and DC filters
- Expected time duration of the fault
- Location of the fault
DC staged faults normally do not require special AC system configurations.
However, to maintain an acceptable level of system security during an AC
staged fault test due to risk of misoperation of some protection relays or
breakers, a special configuration of the AC system shall be generally adopted
with a very specific plan of generation. That may make this type of test highly
costly.
The safe monitoring of many signals is particularly important because this type
of test cannot be repeated many times because of its cost, the stresses on theequipment and for security reasons. For the staged fault tests it is thus highly
recommended to use redundant recorders.
C o p y r i gh t e d m a t er i al l i c en s e d t oE l e c t r i c i t y of V i e t n am b y T h om s on S c i en t i f i c ,I n c
. ( www. t e c h s t r e e t . c om ) .T h i s c o p y d ownl o
a d e d on2 0 1 4 - 0 1 - 0 6 0 8 : 2 8 : 2 8 - 0 6 0 0 b y a u t h or i z e d u s er P h am V an c h i .
N of ur t h er r e pr o d u c t i on or d i s t r i b u t i oni s p er mi t t e d .
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The following signals shall be recorded.
On the system side:
- AC voltages and currents on each phase- DC voltages on both poles
- AC currents in the converter feeders on each phase
- DC currents on each pole and on each DC neutral connection
- AC currents in filter banks
On the controls:
- Main sequencing signals (start-stop, blocking-deblocking, breaker openingand closing orders)
- Crucial protection signals (e.g. overvoltage protection, commutation failure
protection)
- Firing angle order
- Firing pulses on each 12 pulse converter unit
- Alpha and gamma angle measurements
- Current order
Some extra signals may be usefully recorded:
- One valve voltage on each converter unit (that may require specific dividers
to be provided)
- Timing signal allowing synchronization between recordings in the converter
stations and possibly in some generating stations in the vicinity.
For AC faults a limited number of signals need to be recorded on the remote
end, basically DC voltage and current, current order, and firing angle order.
The HVDC power level adopted depends on the AC system configuration
prepared for the test with its associated generation plan.
C o p y r i gh t e d m a t er i al l i c en s e d t oE l e c t r i c i t y of V i e t n am b y T h om s on S c i en t i f i c ,I n c
. ( www. t e c h s t r e e t . c om ) .T h i s c o p y d ownl o
a d e d on2 0 1 4 - 0 1 - 0 6 0 8 : 2 8 : 2 8 - 0 6 0 0 b y a u t h or i z e d u s er P h am V an c h i .
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Staged faults can be dangerous and a special effort should be made to ensure
safe fault throwing equipment and procedures are used.
For application of some faults (specifically in the station) it will be necessary totemporarily install fault throwing switches.
Type of tests:
- Distant phase-to-earth fault and distant 3 phase-to-earth fault: the particular
objective is to assess the sensitivity of the converters to commutation failure.
- Close phase-to-earth fault: the particular objective is to assess the ability of
controls to contain the 100 Hz or 120 Hz ripple on the DC voltage to an
acceptable level, and sometimes to assess the ability to recover rapidly in
case of automatic protective blocking during the fault
- Close 3 phase-to-earth fault: the particular objective is to assess the ability
to re-establish the power flow rapidly.
- AC busbar phase-to-earth fault: same objective as for the close phase-to-
earth fault plus the assessment of possible consequences of fault neutral
current circulation in the earthing grid. This test will also verity the
insensitivity of the controls towards such disturbances and the proper
function of the protection.
- DC line fault: the particular objective is to check the correct response of the DC
line protection and the automatic sequence of recovery. For close faults the ob-
jective is to check the insulation coordination in the DC switchyard. For distant
faults it is to check whether the line protection can differentiate between line
faults and station faults at the remote end. It should also be checked whether
there is any false operation of the DC protection of the sound pole.
Test Acceptance Criteria
- The HVDC system shall remain stable during and after the fault.
- No spurious operation of protection relays either in the DC system or in the
AC system should occur.
- Transient AC and DC voltages shall be contained within the envelope
determined by the insulation coordination study.
C o p y r i gh t e d m a t er i al l i c en s e d t oE l e c t r i c i t y of V i e t n am b y T h om s on S c i en t i f i c ,I n c
. ( www. t e c h s t r e e t . c om ) .T h i s c o p y d ownl o
a d e d on2 0 1 4 - 0 1 - 0 6 0 8 : 2 8 : 2 8 - 0 6 0 0 b y a u t h or i z e d u s er P h am V an c h i .
N of ur t h er r e pr o d u c t i on or d i s t r i b u t i oni s p er mi t t e d .
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- Speed of DC power recovery shall be within the specified time.
- A specified maximum number of commutation failures during a defined time
period shall not be exceeded.
Records should be compared with those obtained by the simulations normally
achieved before the staged faults on site. Differences in response should be
explained.
6.6 Loss of Telecom, Auxiliaries or Redundant Equipment
6.6.1 Loss of Telecommunications between Terminals
Introduction
As indicated in IEC 60919-1, different types of information may be transmitted
between HVDC substations, each type requiring specific performances:
a) Signals for control:
- Power order
- Current order
- Frequency control
- Damping control
- Force retard for the remote station
b) Operation orders:
- Change of control mode of operation
- Operation of switches
- Block/deblock
c) Status indications:
- Position of switches
- Number of converters in operation
C o p y r i gh t e d m a t er i al l i c en s e d t oE l e c t r i c i t y of V i e t n am b y T h om s on S c i en t i f i c ,I n c
. ( www. t e c h s t r e e t . c om ) .T h i s c o p y d ownl o
a d e d on2 0 1 4 - 0 1 - 0 6 0 8 : 2 8 : 2 8 - 0 6 0 0 b y a u t h or i z e d u s er P h am V an c h i .
N of ur t h er r e pr o d u c t i on or d i s t r i b u t i oni s p er mi t t e d .
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– 130 – PAS 61975 © IEC:2004 (E)
d) Measured values
e) Alarm signals
f) Voice communication
g) DC line fault location
The consequence of a loss of telecommunications is related to each of the
above types of information transmitted, furthermore the most critical types of
information are generally transmitted using redundant telecommunication
systems and the tests should address the loss of redundancy.
Most HVDC systems are designed such that loss of telecommunication typically
does not interrupt or significantly modify the existing level of power transmission.
Telecommunications between terminals are used to improve the operating
conditions, the transient performance or to provide some special control facilities
such as frequency or damping control.
The loss of telecommunication should initiate a predefined control sequence that
may end in freezing the power transfer to the pre-fault value.
The objectives and conditions of the loss of telecommunication tests should be
stated bearing in mind these general considerations.
Test Objectives
The general objective of the loss of telecommunication test is to check that when
loosing telecommunication during power transfer or during a start up sequence
the operation of the HVDC system and its effects on the AC system are
compliant with the specification. Message security from external influences such
as noise, etc. should be verified as well.
C o p y r i gh t e d m a t er i al l i c en s e d t oE l e c t r i c i t y of V i e t n am b y T h om s on S c i en t i f i c ,I n c
. ( www. t e c h s t r e e t . c om ) .T h i s c o p y d ownl o
a d e d on2 0 1 4 - 0 1 - 0 6 0 8 : 2 8 : 2 8 - 0 6 0 0 b y a u t h or i z e d u s er P h am V an c h i .
N of ur t h er r e pr o d u c t i on or d i s t r i b u t i oni s p er mi t t e d .
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Test Procedures
It is advisable to perform the tests under the following modes of operation:
a) During steady state operation:
Check the impact on:
- Power order/current order
- Transmitted power
b) During current or power order ramping
c) During start-up and shut-down sequences
The tests are done by disconnecting all end-to-end telecommunication channels
except for operator voice channels at a predetermined instant in time. Message
security should be verified by simulating external noise and/or other
disturbances.
Preconditions
Prior to the tests covered hereafter the proper operation of the
telecommunication system should have been tested during subsystems tests at
site. The function of the control loops and protection circuits should have been
tested with and without telecommunication. The ability of the system to shut-
down safely without telecommunication should have been tested during the end-
to-end tests (see part 4).
The topology of the link, the amount of power transmitted and the sequence of
operation existing when the loss of telecommunication occurs shall be
determined depending on the objective of each individual test.
- During steady state operation and ramping of power/current order: The
HVDC system should be transmitting power at a significant level and operate
under the appropriate control mode.
- During start-up and shut-down sequences: The detailed testing procedureshould be established depending on the specific control strategy.
C o p y r i gh t e d m a t er i al l i c en s e d t oE l e c t r i c i t y of V i e t n am b y T h om s on S c i en t i f i c ,I n c
. ( www. t e c h s t r e e t . c om ) .T h i s c o p y d ownl o
a d e d on2 0 1 4 - 0 1 - 0 6 0 8 : 2 8 : 2 8 - 0 6 0 0 b y a u t h or i z e d u s er P h am V an c h i .
N of ur t h er r e pr o d u c t i on or d i s t r i b u t i oni s p er mi t t e d .
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– 132 – PAS 61975 © IEC:2004 (E)
Test Acceptance Criteria
The loss of telecommunication tests is satisfactory if the HVDC system remains
stable and the effects on the AC systems remain within the specified limits.
No unplanned operation of protective relays should occur.
Start-up and shut-down sequences should terminate safely, with indications
showing the status at which the sequence was terminated.
6.6.2 Loss of Auxiliary Power Supplies Introduction
The auxiliary power supplies of an HVDC substation may be broken down into
three classes according to the level of reliability needed for the performance of
the HVDC system:
- General AC supply with no back-up
- AC supplies with automatic change-over to a back-up AC source
- Uninterruptible supplies including diesel back-up generators
Test Objectives
The tests should verify that short interruptions in the auxiliary supply during
change-over do not disturb the HVDC power transmission and safe and
controlled shut-down of the HVDC substation takes place in the event of a total
loss of all auxiliary supplies except the uninterruptible supply.
The tests should also verify safe shut-down of the HVDC system in case of
failure of the uninterruptible power supply (if any).
C o p y r i gh t e d m a t er i al l i c en s e d t oE l e c t r i c i t y of V i e t n am b y T h om s on S c i en t i f i c ,I n c
. ( www. t e c h s t r e e t . c om ) .T h i s c o p y d ownl o
a d e d on2 0 1 4 - 0 1 - 0 6 0 8 : 2 8 : 2 8 - 0 6 0 0 b y a u t h or i z e d u s er P h am V an c h i .
N of ur t h er r e pr o d u c t i on or d i s t r i b u t i oni s p er mi t t e d .
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Preconditions
Proper function of change-over systems such as automatic undervoltage transfer
should have been checked. Uninterruptible power supply functions, capacity andperformance should have been tested.
Test Procedures - Test Acceptance Criteria
For the AC supplies with automatic change-over, which are used to supply the
cooling fans and pumps and other critical equipment for significant power, tests
should be performed at no load and at full load. The tests should be performedseparately on each type of auxiliary subsystem as follows.
- Loss of the entire AC auxiliary power: the DC system should shut down
safely in a coordinated sequence. If a back-up generator group is provided, it
should start up within the specified time limit and supply the appropriate
load.
- Loss of auxiliary power with automatic change-over: a transfer to the second
AC source will be initiated and the time of change-over will be checked;special care should be given to the restart condition of induction motors.
Special care shall be given to ensure that cooling media flow is not
interrupted longer than acceptable to the relevant equipment.
- Loss of redundant supply of control, protection and communication
equipment: the control and protection equipment should continue to operate
as specified.
- Loss of the entire supply to the control equipment: the DC system shouldshut down safely. For such a catastrophic failure one would normally have to
rely on protective shut-down.
C o p y r i gh t e d m a t er i al l i c en s e d t oE l e c t r i c i t y of V i e t n am b y T h om s on S c i en t i f i c ,I n c
. ( www. t e c h s t r e e t . c om ) .T h i s c o p y d ownl o
a d e d on2 0 1 4 - 0 1 - 0 6 0 8 : 2 8 : 2 8 - 0 6 0 0 b y a u t h or i z e d u s er P h am V an c h i .
N of ur t h er r e pr o d u c t i on or d i s t r i b u t i oni s p er mi t t e d .
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6.6.3 Loss of Redundant Equipment Introduction
HVDC systems may contain various redundant control, protection, and
measuring equipment to enhance system reliability.
Test Objectives
Take-over of the sound redundant element in case of failure should be verified-
The HVDC system should continue to operate as specified.
Preconditions
Proper function of the control and protection system with all redundant elements
in place and functional should have been checked.
Test Procedures - Test Acceptance Criteria
The appropriate tests of this category depend greatly on the redundancy conceptused for the system design under test The tests should simulate the loss of
redundant elements in the failure modes which are the most probable on the one
hand and those which may cause the most onerous conditions for the system.
The tests are successful, if the system responds as designed.
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PAS 61975 © IEC:2004 (E) – 135 –
PART 7: TRIAL OPERATION
General
Introduction
Trial operation provides the opportunity to operate the HVDC system together
with the connected AC systems for an extended period of time. Operation shall
be as close as possible to real operating conditions.
This time period is a particular time of accurate observation of the completeHVDC system and all its components.
The HVDC system will be operated by the owners personnel. Additionally
training of manpower particularly in fault analysis and system performance can
take place.
Test Objective
The purpose of trial operation is to verify the performance and the availability of
the HVDC system during a specified period (typically 2 to 4 weeks) of operation
under real but within specified conditions.
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– 136 – PAS 61975 © IEC:2004 (E)
Preconditions
Before conducting trial operation the following preconditions shall be fulfilled.
- All equipment is available.- All operation and integration tests are completed.
- Operators sufficiently trained to conduct system operation.
- Power transfer schedules between the AC systems coordinated.
- The AC system configurations are within specified limits.
Test Procedure
During trial operation the HVDC system shall be utilized in such a manner as re-
quired by the original design and the owner's intended use.
Typically trial operation is performed for a period of 2 to 4 weeks. During this
period, operation shall be conducted by the owner's personnel and the
manufacturer's assistance shall be limited.
During trial operation accurate observation of the complete HVDC system and all
its components will be carried out.
Any abnormal or unexpected responses or incidents which effects the availability
of the system must be carefully analyzed to determine the cause.
For monitoring and recording purposes the station recorders are sufficient.
These can be complemented by additional recording equipment for the purpose
of collecting data for design study verification.
AC system configuration data shall be available. Should an HVDC system be
built in stages, trial operation could be allocated to the individual stages.
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PAS 61975 © IEC:2004 (E) – 137 –
The tests having no influence on the behaviour and safety of the HVDC system
(radio interference test etc.) can be performed during or after trial operation upon
mutual agreement
Test Acceptance Criteria
During trial operation no forced outages or disturbances due to malfunction of
any HVDC equipment shall occur.
If the need for modifications or adjustments arise during trial operation, action
shall be taken and depending on their extent, a portion of the period of trialoperation or the complete trial operation may have to be repeated.
The criteria for repetition of part or all of the test shall be agreed prior to the start
of trial operation.
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– 138 – PAS 61975 © IEC:2004 (E)
PART 8: SYSTEM TEST PLAN AND DOCUMENTATION
General
Introduction
This part describes the documentation including the system test plan required to
perform the system tests, consisting of:
8.1 Plant Documentation and Operating Manuals
8.2 System Study Reports and Technical Specifications8.3 Inspection and Test Plan
8.4 System Test Program
8.5 Test Procedures for each Test
8.6 Documentation of System Test Results
8.7 Deviation Reports
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PAS 61975 © IEC:2004 (E) – 139 –
8.1 Plant Documentation and Operating Manuals
Plant Documentation is required to provide sufficient up-to-date information on
all equipment installed and its function, location and interconnections.
Up-to-date settings of the control and protection equipment shall be provided.
This shall include the data acquisition system.
The operators should have had sufficient training to be able to execute all
switching and control operations under ail operating conditions with the guidance
of the Operating Manuals.
8.2 System Study Reports and Technical Specifications
System Study Reports shall provide the information needed to operate the
HVDC system together with the connected AC systems within the specified
limits. Particular System Study Reports required for this purpose are for
example:
- AC/DC system interactions- Reactive Power Control
- Protection Coordination
- Control coordination, changing of System configuration and switching
Equipment Specifications will be required to verify the individual equipment
ratings.
8.3 Inspection and Test Plan
The Inspection and Test Plan together with the System Test Program form the
System Test Plan. The Inspection and Test Plan identifies all inspections and
tests to be performed on:
- HVDC station equipment and DC line/cable/bus including the earth electrode
- HVDC control and protection- environmental considerations
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– 140 – PAS 61975 © IEC:2004 (E)
- AC/DC system interaction
- System performance
This guide is structured in a logical sequence and can thus provide background
information for any specific project application.
Each Inspection and Test Plan should comprise the following as appropriate and
similar to this guide:
- Specific objectives per test
- Test procedures (reference to standard procedures)
- Test acceptance criteria
- Preconditions for the Test
- References to system studies on specifications
- References to off-site tests
- Special conditions
All inspections and tests to be performed shall be identified with a unique
number. This number should also be used as cross-reference on all standard
Test Procedures and for the Documentation of the Inspection and System Test
Results.
The Inspection and Test Plan shall also contain all required load levels and load
changes as well as the expected effective short-circuit level (ESCR).
Procedures for each test should be thoroughly discussed with all parties involved
before finalizing the test schedule.
All inspections and systems tests shall be mutually agreed among all parties
concerned well in advance off the actual tests to allow sufficient time for
scheduling. Contingency measures in case of any failure shall also be
discussed.
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PAS 61975 © IEC:2004 (E) – 141 –
8.4 System Test Program
The System Test Program schedules the system tests.
It coordinates the requirements with dispatch authorities and specifies:
- preconditions including environmental and AC systems configuration and
generation schedules;
- preconditions to be selected (control locations, control mode, control level
energy transfer mode);
- initial and final HVDC system configuration;
- energy direction;- power levels, duration and ramp rates.
The System Test Program shall identify the test team and the test leader for
each individual test, for each converter terminal, the load dispatch center,
affected substations or power stations, and test locations where faults or short
circuits are created-
The test schedule should have suitable hold points to check the status ofprotection, auxiliaries and fire protection.
Final permission from the operating authorities shall be requested immediately
before test execution.
Test duration should be planned with an adequate time margin to allow for
contingencies. As system tests have a high potential of causing major
disturbance on the HVDC and the connected AC systems considerations shallbe given to execution during off peak hours.
It is also preferable that the AC systems are configured to have sufficient loading
margin to sustain total HVDC load rejection.
In case of planning staged fault tests ample precaution and support by specialist
staff should be provided including studies showing the effect of faults on the AC
system.
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– 142 – PAS 61975 © IEC:2004 (E)
8.5 Test Procedure for Each Test
The test procedures describe for each individual test the instructions to be
followed by the test team.
The preconditions to be fulfilled and the references to system studies and
specifications or off-site tests are defined.
Test objectives, procedure and acceptance criteria specify the actual
performance of each specific test.
The test procedure also lists the test equipment to be used and the
measurements to be taken, and the exact measurement points. Cross-reference
to the documentation of system test results shall be identified by using a
numbering system. The same numbering system shall also reference the
application of the test procedure and the inspection and teat plan.
The test procedures may be one report, specifically written for the project or an
assortment of generic test descriptions compiled for the project, in case generic
test descriptions are used these should be packaged complete with an index.
8.6 Documentation of System Test Results
A commissioning report describing the results of each test series, together with
the test results, data acquisition traces and data captured by station recorders,
sequence of event recorders printout, alarm printout and other special results
shall form the documentation of System Test Results.
Forms used to sign off successful tests should differ from unsuccessful tests to
be recorded.
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PAS 61975 © IEC:2004 (E) – 143 –
A failed test should be recorded in a failure report which shall have the test
number description and the reason for failure noted. Upon correction of the
problem the manufacturer should briefly describe the modification on the same
failure report and indicate that the system is ready for a retest of the failed test.
All modifications shall be formally tracked according to the applicable quality
assurance procedures in all applicable parts of the documentation.
A detailed description of the modification should be provided in the deviation
report. For tracking the status of failed tests a database shall be kept indicating
the status (new, modification implemented, retested, passed, failed again) of
each test.
A record of equipment outages, malfunctions and diagnostic test results related
to the commissioning shall be kept.
Any special occurrence on the results of any test shall be highlighted by the test
team prior to submitting the commissioning report.
All system test results should be well indexed and referenced to the individual
tests.
8.7 Deviation Reports
The deviation report shall form part of the commissioning report with a detailed
description of modifications and reference to the specific tests and test results.
A discussion of the modifications carried out should be included for furtherreference.
____________
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Standards Survey
The IEC would like to offer you the best quality standards possible. To make sure that wecontinue to meet your needs, your feedback is essential. Would you please take a minuteto answer the questions overleaf and fax them to us at +41 22 919 03 00 or mail them tothe address below. Thank you!
Customer Service Centre (CSC)
International Electrotechnical Commission3, rue de Varembé1211 Genève 20Switzerland
or
Fax to: IEC /CSC at +41 22 919 03 00
Thank you for your contribution to the standards-making process.
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Nicht frankieren
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SUISSE
Customer Service Centre (CSC)International Electrotechnical Commission3, rue de Varembé1211 GENEVA 20Switzerland
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