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MIGRATION STRATEGIES FOR ENABLING THE SMART GRID

By

Manford Kwan, P.Eng.

ASAT Solutions Inc.#8, 2121-29th Street, N.E., Calgary, AB, Canada T1Y 7H8

manford.kwan@asatsolutions.com

ABSTRACT

North American electric power systems are inthe early stages of transforming to the Smart

Grid, a system that combines existing utility

grids with new digital technology to improveoverall system efficiency and supply reliability.

From a substation automation perspective, one of

the immediate trends is the increasing amount ofdata available from substation intelligent

electronic devices (IED) and sensors.

This paper describes the various considerationsfor developing a migration path strategy from

existing substation automation systems to enable

the Smart Grid of the future.

I. INTRODUCTION

As electric utilities plan their Smart Grid vision,

the migration strategy for transforming existing

substation automation systems to smartsubstations is a key component of grid

modernization.

In general, todays substation automation

systems consist of a SCADA/EMS systempolling data from remote terminal units (RTU)

using outdated protocols and slow serial modem

links (1,200 to 9,600 baud). Multi-functionalintelligent electronic devices (IED) are gradually

replacing aging electro-mechanical relays.

Access to non-operational data, if available, iscollected manually or from dial-up modem links

using separate systems.

The smart substation vision generallyencompasses a substation information server that

provides:1. real-time operational data to modern

SCADA/EMS/EMS systems based on IP-

based communication networks;

2. secure remote access to non-operational datafor electric utility enterprise level users;

3. the integration of substation IEDs;

4. state-of-the art visualization tools for

substation dashboards; and

5. platforms for advance substation automation

applications.

One of the benefits of smart substations isunlocking the value of existing and new

substation data to improve operationalefficiency. Smart substations can turn substation

data into understandable and actionable

information to support real-time decisionmaking.

The transformation of existing substation

automation systems to smart substations is anevolutionary process. A well-defined strategy

with flexibility is needed to evolve (migrate)

existing substations to smart substations and toaddress unforeseen or unplanned requirements.

This paper focuses on the five steps of the

migration strategy.

II. EXISTING SUBSTATIONS

Todays existing substation automation systems

today are typically based on the RTU approach.

RTUs report real-time data for the operation ofpower systems back to the SCADA/EMS master

station. Operational data attributes focus on what

and when, and typically status and measurementsare in real time. This data includes: circuit

breaker open/close status, alarms, events with

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time tags, line currents and bus voltages. The

corresponding action of operational data isprotection, control and SCADA. The main users

are power system operators.The limitations of the RTU-based approach arethe lack of IEC 61850 support, networking

capability, visualization tools, and remote access

to non-operational data.

III. STEP 1: SUBSTATION SERVER

The first step in the migration path starts with the

substation server.

The substation server is inserted between the

SCADA system and the RTU. It must appear to

be an RTU to the SCADA system, and appear tobe a SCADA system to the RTU by emulating

the respective client or server components of thecommunication protocol. No changes to the

SCADA system and RTU are necessary.

Although the substation server acts in atransparent mode, this is a fundamental step in

providing flexibility to the migration strategy.

Benefits:By taking this simple first step, utilities now

have the options and flexibilities to:

x phase in a new master station with modernprotocols such as DNP 3.0 and/or IEC

60870-5-101/104;x replace the existing RTUs with new RTUs

using modern protocols;

x integrate data from new substation IEDs andreduce dependency from the substation RTU

I/O; and

x increase visibility with the integrated HMI

function providing substation dashboards.

Considerations:

x Due to the mission critical nature of the

server, the hardware must be a substation

hardened platform with no fans, no movingparts, and redundancy as a must for critical

substations.

IV. STEP 2: IP-BASED NETWORKS

The second step is to add in IP-based

communication networks such as WANs for

remote access and LANs for substation devices.

With the emerging acceptance and support of IP-

based network communications, this provides the

backbone of the data exchange outside and insidethe substation. The increased bandwidth

capability allows a more efficient transfer of

substation information to the enterprise level

applications and users. Ethernet capability isnow standard on the new generation of

substation IEDs.

Benefits:

x the substation LAN allows for easyintegration of Ethernet-enabled substation

devices;

x the increased bandwidth of the WAN allowsfor more efficient transfer of non-

operational data, such as setting files, faultand waveform captures, and substationdashboards; and

x the IP-based system allows for easyintegration of enterprise level applications

and users in a secure manner.

Considerations:

x cyber security functions such as

authentication, firewalls, routing and user

access logs can be addressed with thecombinations of rugged servers, routers, and

switches; and

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x substation hardened switches and routers

provide the backbone of substation data

traffic; the bandwidth should be a minimum

of 10/100 Mbit/s and flexible redundantnetwork configurations should be supported.

x The enhanced communication infrastructure

should minimize firmware/database changesto the existing SCADA system and RTU to

avoid unnecessary testing.

V. STEP 3: IED INTEGRATION

The substation server acts as a data concentrator

to integrate data from the existing and new IEDs.Substation IEDs can be sensors, protection

relays, PLCs, and RTUs.

Existing

SCADA/EMS

Substation

Server

Serial Modem

Link

Existing

Remote

Terminal Unit

(RTU)

Serial Link

IP based

Network

y

Remote

Access

y

WAN

RELAY PLC METER

Station bus ( RS232, RS485, LAN)

The data concentration function of the substation

server retrieves real-time data from thesubstation IEDs using standard or proprietary

communication protocols. In addition to real-

time data, valuable non-operational data is alsoavailable from the substation IEDs.

Non-operational data is the historical data, files

and records that focus on what and why, andtypically include counts, accumulation and

trends. This data includes fault and waveformrecords, circuit breaker operation counts andcontact wear, as well as transformer dissolved

gas, moisture and temperature. The primary

objectives of non-operational data are equipment

maintenance, system planning and assetmanagement. The corresponding action of non-

operational data is analysis, prediction and

planning. The main users are equipmentmaintenance, asset management, system

planning and system operation.

Benefits:

x unlocks the valuable substation information

that is normally trapped inside the IED;

x reduces the dependency on the RTU I/O byusing real-time data such as analog anddigital inputs from the substation IEDs; and

x provides non-operational data for analytics.

Considerations:

x for real-time data, open protocols such asDNP 3.0, IEC 60870-5-101/103/104, and

IEC 61850 should be used; for some older

IEDs, industrial standard Modbus protocolor their native proprietary protocols can also

be used;

x communication to the IED can be serial

based (RS 232 or RS 485) or IP based;

x for non-operational data, files can beaccessed using the IED vendor-specific

software or by file transfer mechanisms such

as FTP; and

x open systems that supports multi-vendorIED and multi-vendor protocols.

VI. STEP 4: SUBSTATION

DASHBOARDS

Once the substation data is integrated and

available at the substation server, the next focus

is how to present the data in an understandableand actionable format to the utilitys various

departments.

Typical substation dashboards are:

x single line diagrams and annunciator panels;

x transformer monitoring: on-line dissolved

gas analysis, moisture in oil, etc.;

x partial discharge monitoring;

x circuit breaker monitoring;

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x information from protection relays: distance

to fault, percentage wear of circuit breakers,

etc.; and

x information from RTUs: communicationerrors, health of the RTU modules.

Benefits:

x substation data presented in a graphical

format turns data into easy to understandand actionable information;

x higher bandwidth provides efficient transfer

of substation dashboards and non-

operational data files from substation toenterprise level;

x equipment monitoring provides flexibility to

migrate from time-based maintenance to

condition-based maintenance; and

x remote access reduces unnecessary trips tothe substation.

Consideration:

x In addition to cyber security, the substation

server must also provide the capability todefine access levels for various departments.

VII. STEP 5: ADVANCED

APPLICATIONS

This final step is to address specific advanced

applications of the smart substation.

Modern

SCADA/EMS

Substation

Server

y Enterprise

Applications

RELAY PLC METER

Station bus ( RS232, RS485, LAN)

IP based

NetworkWAN

y

RTU

Real TimeData

Substation

HMI

Substation

MaintenanceEngineering

Asset

Mgmt

Advanced applications are:

x phases in the next generation of the

SCADA/EMS system;

x for critical substations, the substation server

supports redundancy with seamless transfer;

x supports IEC 61850 migration: GOOSE

messaging from substation server to the

substation IED, MMS support to retrievedataset from IED, and support of SCL;

x substation automation: Volt/VAR control,

interlocks at the bay level and station level;

and

x distribution automation: integrating datafrom pole top switches provides faultdetection, isolation and auto-restoration.

VIII. SUMMARY

The Smart Grid vision has the following

characteristics:

x flexibility: allowance to meet unforeseen or

unplanned requirements;

x secure open access of substation

information: integration of islands ofautomation;

x integrity: a high level of reliability, usability,

and quality;x ease of use: user friendly visualization tools;

x openness: supports multiple vendor devices,from legacy to new devices;

x cyber security: systems must be protected;

and

x scalable: from a single to multiple server

units with incremental upgrade paths.

The key benefit of smart substations is unlockingthe value of existing and new substation data to

improve operational efficiency.

IX. SOURCES AND REFERENCES

1. McDonald, J.D., Substation Integration and

Automation, Electric Power SubstationsEngineering, Second Edition

2. Wong, D. Unlocking the Benefits of Non-

operational Data for the Maintenance andManagement of Critical Substation Assets

3. www.asatsolutions.com