TEPCO's experiences of automatic voltage …sites.ieee.org/pes-resource-center/files/2014/03/PESGM...TEPCO's experiences of automatic voltage controllers and SIPS as measures to prevent

1©2007　The Tokyo Electric Power Company , INC. All Rights Reserved

TEPCO's experiences of automatic voltage controllers and SIPS as measures

to prevent massive power outages

Shinichi Imai, [email protected]

Teruo [email protected]

The Tokyo Electric Power Company, Inc.


Hokkaido EPCO

Hokuriku EPCO

Chubu EPCO

Chugoku EPCO

　Okinawa EPCO

　Kyushu EPCOShikoku EPCO

Kansai EPCO

　　　ＴＥＰＣＯ　　　　　Tokyo EPCO

Tohoku EPCO

North Latitude

Wholesale: J-POWER (EPDC)The Japan Atomic Power Company, etc.

East Longitude

Date of Establishment:May 1, 1951

No. of Shareholders:801,025

Electricity Sales:¥4,630 billion(Approx. US$38.6 bil.)

No. of employees:38,235

No. of Customers:27,780 thousand

Corporate Outlineas of March 31, 2006

75.3 GW Generations–14.1GW; Hydro–10.3GW; Oil Fired–3.2GW; Coal Fired–27.7GW; Gas Fired–18.2GW; Nuclear

The Tokyo Electric Power Company, Inc

1,572 Transmission Substations28,693 circuit kilometers of transmission lines.27.5 million electric customer accounts.Peak System Load – 64.3 GW, 280 GWh


Contents• Background; TEPCO’s SIPS• Observations on recent blackouts and related

controllers & schemes in TEPCO– August 14, 2003 Northeastern U.S. blackout– Automatic Voltage Controllers and UVLS in TEPCO– November 4, 2006 European blackout– Adaptive load mitigation schemes & UFLS in TEPCO

• TEPCO’s SIPS against short term instability and actual operational experiences– Islanding protection system with P&Q balancing

control– 1999 and 2006 Tokyo power outages

• Summary


BackgroundTEPCO’s System Integrity Protection Schemes


TEPCO’s SIPS

• Shunt switching• Load shedding

System Islanding

• Fast generation rejectionTransient Instability

• Tripping of pumped-hydros• BTB controls• Load shedding; UFLS

Frequency Drop

• High side voltage control; PSVR• Shunt switching; VQC• Load shedding; UVLS

Voltage Instability

• Bus-coupler switching• Tripping of pumped-hydros• Generation runback/pickup• Load shedding

Overloading

Automatic actions by SIPS


Features of TEPCO’s SIPS• Flat and centralized architecture inside substations or covering coherent subsystems

• Response based actions using on-line informationrather than pre-determined actions like traditional RAS

• 2 out of 3 or 3 out of 4 voting redundancy ensuring security and dependability

• Custom designed microprocessor based relay and controller without using SCADA based information rather than utilizing industrial purpose Programmable Logic Controllers

• Based on co-development project with Japanese relay manufactures


Observations on recent blackouts and related controllers &

schemes in TEPCO


Observations on 2003 US Blackout

• The loss of the Eastlake 5 unit did not put the grid into an unreliable state. However, the loss of the unit required the utility to import additional power to make up for the loss of the unit’s output (612 MW), made voltage management in northern Ohio more challenging, and gave FE operators less flexibility in operating their system. (Final Report by US-Canada TF)

• After the loss of Sammis-Star 345kV line (Event 8), the voltage began a severe decline, which means n-8 contingencies caused voltage instability. (ECAR report)

• Installing shunt capacitors to transmission level can avoid tripping of critical generator


Coordination of voltage schedule and automatic voltage controllers in TEPCO

• Transmission voltage schedule maintained High & Flat by reactive supplies from Gens and MSCs at S/Ss• 50% at Gens and 20% of MSCsreserved in peak demand• High side voltage control (PSVR) at reinforces reactive supply capabilities of Gens• Fast switched shunts with numerical controllers can be regarded as dynamic resources• Power system performance can be ensured against unexpected contingencies by a response-based control• Automatic controllers effective to relieve operator’s burden during emergency to stop or limit cascading

AVR

PSVR

AVR AVR AVR

VQCTap changing

Switching Switching

550kVSummer Peak

535kVSummer Peak

545kVNormal

525kVNormal

500kV power grid

Shunt Shunt Shunt Shunt

PSVR PSVR PSVR


UVLS as Last Resort• Installed just after 1987 Tokyo

Blackout: Longest operation history of the world

• Microprocessor-based relaying• Voltage collapse is detected:

– by central units located in the 500kV network, because 275kV or lower voltage are regulated by tap changing

– based on 3 out of 4 decision making logic to avoid unwanted operation

• Central units detect:– Voltage Drop (Under Voltage)– Rate of Voltage drop (dV/dt)

500kV Main Grid

CUCU

CU

Communication; Voltage collapse detection result

Communication; Measured 500kV voltages

(CU: Central Unit)

Sub-Station275,154/66

275kV,154kV radial network

CU

Sub-Station275,154/66

RTU

RTU


Observations on 2006 European Blackout

• Overloading;– The overloading mitigation action led to result which was contrary

to what operators expected

• Possible solution for overloading;– Automatic mitigation to relieve operator’s burden during

emergency and to avoid cascading– Actions would be adaptive in step by step manner with priorities

until the overloading would be relieved.

• Frequency decay in western Europe– Missing import from the East of 8940MW resulted total shedding

of 17000MW of loads and 1600MW of pumps– Coordination of underfrequency shedding/tripping schemes among

TSOs may be reviewed to reduce the customer interruptions as much possible.


TEPCO’s OLR (Overload Relay)Automatic load mitigation scheme

OLR

When transmission lines ortransformers are overloaded

Send outcontrol signal

Generation Stations

• Rapid Output Control• Selective Generator Shedding

Substations• Load Shedding

• Generation controls with faster time delays executed prior to load shedding with slower time delays• Automatically Relieve Overload in Network FacilitiesPrevent Unnecessary Trippings and Outages


• Increase timer settings for each frequency level.

• Shed load step by step.

TEPCO’s UFLS with various time delays

Settings Time Delay Shed loads48.5

(58.2)Hz

0.5s 4%1.0s 4%2.0s 4%3.0s 4%

9.0s 4%48.0

(57.6)Hz

0.2s 8%0.5s 8%1.0s 4%2.0s 4%

6.0s 4%

40%

40%

Time

Level2

Variable timers

Level3

Shed load

Level1

Frequency

Time

Level2

Level3

Variable timers

Shed load

Level1Variable timers

Frequency (Level2)

(Level3)


TEPCO’s SIPS against short term instability and actual operational

experiences


Power system supplying to central Tokyo area

• SAIDI for Central Tokyo Area is less than one minute• Radial operated to avoid high fault current and can be

switched to adjacent system from different 500kV substations. Neither series reactors nor FCLs.

• Easy to know contingency flows, no loop flow problems and no cascading outages. No need for on-line contingency processor.

• Loss of parallel circuits on single tower can cause power outage in downstream system, which can be restored within 30 to 60 minutes by manually switched to adjacent system in each voltage level of 275, 154 and 66kV.

• Some amounts of generators connected to 154kV power systems in Tokyo bay area.

• Some systems including power stations are intentionally islanded with vital area by SIPS(UPSS).

• Training for operators is critical for fast system restoration.


Metropolitan Area including Tokyo

TEPCO’s bulk power gridＧ

Ｇ

Ｇ

Ｇ

Ｇ

　

• 500kV; Meshed configuration and meshed operation

• 275kV and below; Meshed configuration and Radial operation

500kV

275kV

500kV

500kV


Bulk power system configuration in central Tokyo area

500kV Bulk Power Backbone

Central Tokyo Area

275kV OH Double Circuit TowerCaps; 3 to 4 GW

275kV UG Triple Circuit LinesCaps; 1 to 2 GW


Bulk power system configuration in central Tokyo area

500kV外輪系統

275kV都心導入架空送電線



500kV架空送電線275kV架空送電線275kV地中送電線

凡例

A変電所

B変電所

C変電所 D変電所

E変電所

F変電所 G変電所 H変電所 I変電所

J変電所 K変電所

L変電所 M変電所

Normally Opened


500kV Power Grid

IntentionalIslandingCUCU

RTURTU

～～ L L L L LL

L

RTURTU

Generators Load

LoadShedding

Sh.R

C ssD ps B ss

Load

Load Shedding

154kV

275kVA ss

ShR

Loss of mains

500kV

275kV

LoadShedding

(NOTE)

Metropolitan Area

RTURTUShR

switching

RTURTU

UVR, UFR, ∆f

UVR, UFR, ∆f

UVR, UFR, ∆f

UVR, UFR, ∆f

RTURTU Remote Terminal UnitMeasures P and Q.Trips feeders based on the command from CU.Opens or closes shunts and cables based on the command from CU.

CUCU Central UnitDetects system separation.Calculates the balance of P and Q.Sends commands to RTUs.

500kV & 275kV Overhead Transmission Line275kV Under-ground Cable Line154kV Under-ground Cable Line66kV Under-ground Cable Line

Radial System

Grid Network

Conceptual Diagram of UPSS


UPSS Controls both P and Q balance of Islanded System

• P Balance– To Maintain the Frequency of the Islanded System.– Shed Proper Amount of Load.

• Q Balance– To Maintain Proper System Voltage. – Switch on and off shunt capacitors and reactors.– Switch off Cables if shunt control is not enough.

• UPSS watches the system condition every 2 seconds and determines how to control if the system becomes islanded.


No.1 line No.2 line

No.1 Line No.2 Line

Faults

Faults

Faults

Actual Operation of UPSS on August 14, 2006• Outline of the Outage

– Date: August 14, 2006– Interrupted Power: 2,160MW (1.39 million households are affected.)– Area: A portion of Tokyo metropolitan area and neighboring area– Duration: 0 - 59min– Cause: One of 275kV major routes is Lost.– Islanded System Scale: 620MW (310MW ACC Generator x 2)


No.1 Line No.2 LineUpper Phases

Middle Phases

L ower Phases

Distance between lower phases and

surface of the river 16.2m

No.1 Line No.2 LineUpper Phases

Middle Phases

L ower Phases

Distance between lower phases and

surface of the river 16.2m

Conductors of lines were severely damaged

A Crane Vessel Crashed into Transmission Lines.

(53feet)


Main Grid

G G G

3T 2T 1T

G GG1-3 1-11-2

P: 1,440MWQ: -40MVar

P: 668MWQ: -345MVar

Double circuit lines triped

Shed Load: 666.5MW, -268.5MVarSwitch on Shunt Capacitors: 80MVarSwitch on Shunt Reactor: 70MVarTrip Cable including Tr: 163MVar

Shed Load Shed Load Shed Load

Shed Load Shed Load

Shed LoadShed Load

No.1 Cable Off

UPSS controlled PQ balance to maintain the islanded system

Outage Area: 839MWMain Grid

275kV Bus275kV Bus

275kV Cable

P: 620MW

2 ACC Units

154kV Bus 154kV Bus

66kV Bus

154kV Bus

66kV Bus

154kV Bus

66kV Bus

154kV Bus

66kV Bus

Q1: 146MVarQ2: 311MVar

ShR On

ShR On

SC On

Outline of UPSS Operation Result


UPSS Detected System Separation in 0.4 Secondby Exceeding Phase Angle Difference.

48.648.8

4949.249.449.649.8

5050.250.4

7:37:52.0 7:37:52.5 7:37:53.0 7:37:53.5 7:37:54.0Time

Freq

uenc

e[H

z]

-20020406080100120140160

Phas

e An

gle

Diff

eren

ce

Setting(110 )

System Separation

0.4Sec

Phase Angle Difference

Main Grid Frequency

Islanded System Frequency

Freq

uenc

y[H

z]

Phas

e An

gle

Diff

eren

ce


The Frequency and Voltage of the islanded system recovered in a few seconds.

0.6

0.7

0.8

0.9

1

1.1

1.2

7:37:50 7:37:52 7:37:54 7:37:56 7:37:58 7:38:00 7:38:02

Time

Volta

ge[P

U]

48.4

48.8

49.2

49.6

50

50.4

7:37:50 7:37:52 7:37:54 7:37:56 7:37:58 7:38:00 7:38:02T ime

Freq

uenc

y[H

z]

Islanded System Frequency

Voltage of BUS B

System Separation

Voltage of BUS A

Nominal Frequency(50Hz)

Fault

Nominal Voltage(1PU)


The Most Important Area

～～～～

Air Plane Crash

Another UPSS Operation historyon November 22, 1999

400MW

49.5

49.6

49.7

49.8

49.9

50.0

50.1

50.2

50.3

50.4

50.5

13:40 13:42 13:44 13:46 13:48 13:50 13:52 13:54 13:56時刻

Hz 本系統都心単独系統

13分

51.2Hz

47.63Hz 13 minutes

System SeparationSynchronized

Main grid Islanded system

Outage Area

1.6GWLost

Islanded Area

to main grid


mm,f θ

UPSSactivateUPSS

(Urban Power System

Stabilizer)

Islanding System Automatic Synchronizer

Detect the system

islanding

Command to reconnect the islanded area and Main grid

275kV

154kV

Power Plants

Substations

66kV154kV

Command to close

disconnectors

Check the synchronizing condithion Δｆ< 0.3HzΔｆ is decreasing

Close circuit breakers at the timing of Δ is nearly 0.

Islanded Area

Main Grid

Synchronizing Point275kV

Loads

Open

Close ii ,f θmm,f θ

･ Now: We rely on manual operation for system reconnection.･ Near Future: System reconnection will be done automatically.

Islanded System Automatic Synchronizer

ISAS is now under development and will commence operation in July, 2007.


Challenges for future• Retaining and keeping expertise especially for

system design and testing• Accelerated obsolescence of microprocessor

based technology and spare parts problem• Utilization of standardized technologies, products

and communication protocols• Sophisticated automated system restoration• Coordinated setting and tuning among voltage

controllers and SIPS by conducting many numerical calculations by more efficient manner

• Utilization of fast, reliable and high accurate data and information collected from whole of TEPCO’spower system with synchronization.


Questions or Comments


VQC (Voltage Q Controller)

275kV Bus voltage

DEADBAND

SC offShR on

SC onShR off

Down Tr tap

Raise Tr tap

500kV Bus voltage

500kV Bus

275kV BusSC, ShR switch

Tap change

Detect Voltage

VQC

VQ Controller automatically controls Trtap and Shunts according to Bus Voltages

Basic concept of VQ Control


• Detect high-speed rate of frequency decline.

• For fast load shedding in case of large L-G imbalance.

• Measures Tc instead of df/dt.

Relaying Algorithm for Rate of Change of Frequency

ROCOF settings Shed loads49.0

(58.8)Hz

2.0s 8%

1.0s 16%

0.5s 24%

0.4s 32%

48.0(57.6)Hz

Time

FrequencyLevel1

Level3Shedload

Shed load when Tc isshorter than setting.

Tc


Effect of ROCOF and Level+Timer

Time Frequency characteristic

• Lowest frequency is raised (improved).• Accommodate to TEPCO’s policy in case

of severe L-G imbalance such as 40%.

(in TEPCO’s policy)Lowest tolerant frequency


How to Detect System Separation?• Phase Angle Difference between Islanded System

and Main System

• Voltage Sag of Islanded System

&

>1Voltage of Islanding system < 0.6pu (Sagged)

Voltage of Main grid> 0.94pu (Normal)

Phase Angle Difference>110

(Avoid Unnecessary UPSS operation during faults.)

&

Distance Relay

Activate UPSS

Note: Not Just Checking Status of the specified CBs.Whatever the system configuration is, UPSS must be able to detect system separation properly.


Measurement of phase angle difference• Synchronized Sampling

• Calculation of Phase Angle Difference

Note: We don’t rely on GPS for vital protection systems.

Va

Vb

Synchronized

Va･Sin( + -90 )Va･Sin( + )

Vb･Sin( )

Vb･Sin( -90 )

90

Va(m)=

Va(m-3)=

Vb(m-3)=

Vb(m)=

Va(m)･Vb(m) + Va(m-3)･Vb(m-3) -1|Va|･|Vb|

=Cos ( )

Va･Sin( + ) Vb･Sin( ) + Va･Sin( + -90 ) Vb･Sin( -90 )x x

=Va･Vb･Cos( + - )

=Va･Vb･Cos( )

=Va･Sin( + ) Vb･Sin( ) + Va･Cos( + ) Vb･Cos( )x x

Master unit

Slave unit Timin

g Fla

g

TmT

Timing Flag

TsT

Sampling Interval

Assume delay times of both Upstream and Downstream are the same.

T Ts - Tm2= 0 (Adjust Sampling Timing)

Sampling Interval

Sampling


P

Failure

Main Grid

PowerStation

L L

L L

SubstationSubstation

SC

L L

ShR

α

Substation

L

L L

X～

～

β2

Q1 Q2

β1

L

275kV154kV 275kV

275kV154kV

66 kV

66 kV

Substation

P: Excess Active Power which was received from the main grid. The same amount of load must be shed to maintain the frequency.Q1, Q2: Reactive Power which was passing the central transformer of the islanded system must be maintained to keep voltage proper.

α : Detection point of receiving Active Powerwhich is used for Load shedding Calculation.

β : Detection points of passing Reactive Powerwhich is used for Voltage Control Calculation.

Simplified Power System Model for Active & Reactive Power Balance Calculation

Documents

TEPCO's experiences of automatic voltage …sites.ieee.org/pes-resource-center/files/2014/03/PESGM...TEPCO's experiences of automatic voltage controllers and SIPS as measures to prevent