MULTI AGENT-BASED ON-LINE DIAGNOSTIC SCHEME

OF SUBSTATION IED

Seong-Jeong Rim and Seung-Jae Lee

Next-generation Power Technology Center(NPTC), Myongji University, Yongin, Korea

Keywords: Multi-agents, On-Line Diagnosis, SA (substation automation), IED (intelligent electronic device).

Abstract: This paper presents a novel multi agent-based diagnostic scheme of substation IED. The proposed method is

the on-line diagnostic scheme for the IEDs in IEC61850-based SA system using multi-agents. Multi-agents

detect the fault of IED installed in substation and apply to improvement of reliability in protection and

control system of substation. These agents in the SA system embedded in the station unit, the engineering

unit, the trouble manager, backup IED and protection and control IED as the thread form. Through the

implementation and the case studies of the proposed scheme, the availability is proven.

1 INTRODUCTION

IED (intelligent electronic device) mis-operations,

such as failing to isolate a faulted line or incorrectly

tripping a healthy line, are involved in major

disturbances within power systems and can lead to

catastrophic cascading events or even blackouts

(Bertsch, J. et al. 2003). Giving IEDs the ability to

diagnose would be a significant addition at critical

locations in the power system by helping to reduce

the number of mis-operations.

The existing diagnostic method of IED mainly

uses off-line TBM (time-based maintenance) or

CBM (condition-based maintenance) (Yu X.Z. et al,

2000). Especially IED doesn’t operate in normal

condition and operate it when the disturbance occurs

in power system. It is hard to determine the fault

condition before IED is tested.

On the other hand, the conventional scheme to

improve the IED’s reliability, have the redundant

structure as the backup device (Ding M. et al.,

2004). Redundant structure employs the dual device

with the same function so that improves the

reliability of the system. However, this system has

the drawback which not only increases the

probability of mis-operation but cost. Thus, the

improvement scheme of the reliability is required to

overcome these problems.

In this paper, a novel multi agent-based

diagnostic scheme of substation IED is proposed.

This method is the ODS (on-line diagnostic scheme)

for the IEDs in IEC61850-based SA system using

multi-agents (IEC 61850, 2002-2005). Multi-agents

detect the fault of IED installed in substation and

apply to improvement of reliability in protection and

control system of substation. These agents in the SA

system embedded in the station unit, the engineering

unit, the trouble manager, backup IED and

protection and control IED as the thread form.

Through the implementation and the case studies of

the proposed scheme, the availability is proven.

2 IEC61850-BASED SUBSTATION

AUTOMATION

The scheme presented in this paper used many

features of IEC61850 to diagnose the substation

IED. The typical features of IEC61850, which make

our scheme possible, consists of the network based

data transfer (process bus), the standardized

interface and SCL (Substation Configuration

Language)-based engineering.

2.1 Process Bus

In the existing substation protection and control

system, analogue data such as voltage and current

are fed into protection relays from CT and VT which

are installed on the primary protection equipments

such as transformers and circuit-breakers. In the

216

Rim S. and Lee S. (2007).

MULTI AGENT-BASED ON-LINE DIAGNOSTIC SCHEME OF SUBSTATION IED.

In Proceedings of the Fourth International Conference on Informatics in Control, Automation and Robotics, pages 216-219

DOI: 10.5220/0001647202160219

 SciTePress

Devices

(IEDs)

System

Configurator

Single Line

Diagram

Functional

Specification

Device Selection

IED

Configurator

ICD file

(IED

Capability

Descrip.)

SCD file

(Sys. Config.

Descrip.)

CID file

(Config. IED

Descrip.)

SSD file

(Sys. Spec.

Descrip.)

IEC61850 based SA system, analogue signal will be

converted into digital data by the process IED

installed on the primary protection equipment and be

sent to the bay IED through the process bus (Fig.1).

The largest difference between the two schemes

above is whether the data transfer path can be

changed during operation. In the existing system,

analogue data are transferred through hardware, so

data transfer path cannot be changed unless the

physical connection is changed. In this scheme, data

are transferred on process bus, so the data transfer

path can be changed by changing the destination of

data packet.

Figure 1: Structure of IEC61850-based SA System.

2.2 SCL-Based Engineering

For integration of various IEDs, IEC61850 suggests

a standard engineering technique. The key is in two

softwares called system configurator and IED

configurator. Figure 2 shows the course of

IEC61850 engineering. First, system configurator

gets all the information about the substation from the

SSD (System Specification Description) file that

contains system related information and the ICD

(IED Capability Description) file that contains IED

related information, and creates the SCD (Substation

Configuration Description) file that configures the

function and data flow for each IED. All the files

mentioned above are made by XML-based SCL. An

IED configurator receives the SCD file and creates

CID (Configured IED Description) file that contains

the format suitable for IED. Finally to download

CID file, each IED is able to communicate with

among them.

In this scheme, when an IED error is detected, it

reconfigures its data path so that the data that were

transferred to bay IED is now transferred to the

backup IED. The reconfiguration is feasible because

of the SCL based engineering.

Figure 2: SCL based engineering.

2.3 Standardized Interface

In IEC61850, all the information about a substation

is modelled into a standard interface called LN

(Logical Node). Data exchange between these IEDs

is possible as long as all these IEDs follow the

standard LN interface regardless of IED hardware

structure or algorithm. For example, if there are two

distance relays made by different companies, whose

signal filtering, calculation of RMS, error detection

algorithm, and hardware are different, the two relays

can be exchanged when they use the same services

and the same LN interface.

3 MULTI AGENT-BASED

ON-LINE DIAGNOSTIC

SCHEME

3.1 On-Line Diagnostic Scheme

The structure of the ODS (on-line diagnostic

scheme) is shown in Fig. 3. Note that the station

unit, bay IED, process IED, and engineering unit

constitute the substation automation system, which

follows IEC61850 standard. Backup IED and trouble

manager are added to the system to implement the

ODS. Trouble manager is in charge of detecting the

IED error by sending a test pattern to bay IED and

comparing the results with expected ones. Backup

IED is a redundant IED that downloads software

from engineering unit and then starts to operate

when error is detected on bay IED.

The TM (trouble manager) periodically checks

the functions of each bay IED to determine whether

the IED has an error. The fault detection procedure

in trouble manager is as follows:

Station

HMI

Engineering

Unit

Bay

Controller

IED

Intelligent

Switchgear

Non-conventional

CT/VT

Station level

Bay level

Process level

Station bus

Process bus

MULTI AGENT-BASED ON-LINE DIAGNOSTIC SCHEME OF SUBSTATION IED

217

1) EU (engineering unit) assigns the DUT (device

under test) and inform to TM.

2) TM transfers the information such as LN, preco

nfigured control block and settings for the DUT

to backup IED.

3) TM starts the sample value path from process IE

D #1 to backup IED.

4) TM stops the sample value path from process IE

D to DUT.

5) TM sends the test input pattern to DUT via proc

ess bus.

6) DUT sends the response for the test input patter

n to TM.

7) TM notifies the fault status of the DUT to statio

n HMI if TM detects the abnormal status of DU

Figure 3: Structure of ODS.

If no fault is detected on DUT, TM requires EU

to reconfigure the system to recover the original

operation of DUT and then continue to check next

IED. Also if fault is detected, system waits for

repairing. Backup IED will replace the failed DUT

until it is repaired.

3.2 Structure of Multi Agent-Based

ODS

The proposed method uses several agents which

distributed in a protection/control IED. This method

detects the IED fault and replaces IED to be tested.

In order to operate efficiently, these distributed

systems, agents have the functionality which

autonomously interacts between them. Figure 4

shows the proposed multi agent-based ODS

structure.

As shown in figure 4, the multi agent-based ODS

structure consists of data source, data storage,

communication mechanism and data consumer.

When agents detect the fault of IED in protection

system, it replaces faulted IED and operates with

backup IED properly.

Figure 4: The proposed multi agent-based ODS structure.

Table 1 list a types and functionality of multi-agents

required for performing the multi agent-based ODS.

Table 1: Types and functionality of agents.

Types Duty Ability

Fault

detection

Detect the fault of DUT

Send the test

pattern, Create the

expected result,

Compare with actual

result

Replace

Replace DUT with

backup IED

Control the

communication

service

Response the required

information

Add the information

to DB, Response for

query

User

Assign the IED to be

tested and display the

fault

Display the

information,

Transfer the query

Backup

Perform function of the

DUT

Perform the function

of DUT

IED

Perform function of

protection/control IED

and communicate with

other agents

Response for the

request

Station Bus

Process Bus

Station

Unit

Engineering

Unit

Bay IED

(DUT)

Backup

IED

Trouble

Manager

Process

IED #1

Process

IED #2

HMI platform

agent

User

agent

Fault

detection

agent

Replace

agent

IED

agent

Backup

agent

Substation

User

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218

The agents listed in above table communicate

each other with MMS (Manufacturer Message

Specification) instead of ACL (Agent

Communication Language), since the agents

embedded in IEC61850-based SA system.

4 CASE STUDY

4.1 Test System

Figure 5 shows the test system to verify the

performance the multi agent-based ODS. The part

inside dotted line in this figure means the additional

equipments to conventional SA system.

Figure 5: Test system.

In the test system, HyperSim (real-time

simulator) uses to generate the fault in power system

(HyperSim). MU (merging unit) transfers the digital

signal to protection IED (OCR/Recloser) via

network after it had A/D conversion. Actuator has

the function such as on/off of circuit breaker as

process IED. Backup IED performs the same

function of DUT.

4.2 Simulation: DUT Diagnosis

In this simulation, we consider two types of fault

such as communication and IED hardware part. We

assume that the fault in communication part is LAN

cable broken and the fault in IED hardware part is

power off.

We perform the test that TM can detect the fault.

After the DUT’s function replaces with backup IED,

TM sent the test input pattern and received the

response from DUT. Figure 6 shows the GOOSE

message from DUT as response.

Figure 6: Response message from DUT.

5 CONCLUSION

A novel multi agent-based ODS can be applied in

the IEC61850-based SA system is proposed in this

paper. The technique presented in this paper detects

the fault of IED automatically and it replaces the

failed IED by backup IED to tolerate the fault in

system level. Through the implementation and the

case studies of the multi agent-based ODS, the

availability is proven.

ACKNOWLEDGEMENTS

This work was supported by the ERC program of

MOST/KOSEF (Next-generation Power Technology

Center).

REFERENCES

Bertsch, J. et al. 2003, “Experiences with and perspectives

of the system for wide area monitoring of power

systems,” CIGRE/IEEE PES International

Symposium, Quality and Security of Electric Power

Delivery Systems, 8-10 Oct. pp.5-9.

Yu, X. Z. et al., 2000, “Condition Monitoring of a power

station,” International Conference on Power System

Technology, Vol.2, 4-7 Dec., pp.1029-1033.

Ding M. et al., 2004, “Reliability analysis of digital relay,”

Eighth IEE International Conference on Developments

in Power System Protection, Volume 1, 5-8 April,

Vol.1, pp. 268 – 271.

IEC 61850, 2002-2005, Communication networks and

systems in substations.

HyperSim, http://www.transenergie-tech.com/en/

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