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
Copyright
c
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
X1
IED
X2
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
T.
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
DB
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
1
2
3
4
5
6
7
Process
IED #1
Process
IED #2
HMI platform
DB
agent
User
agent
Fault
detection
agent
Replace
agent
IED
agent
Backup
agent
CT
VT
Substation
DB
User
ICINCO 2007 - International Conference on Informatics in Control, Automation and Robotics
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/
MULTI AGENT-BASED ON-LINE DIAGNOSTIC SCHEME OF SUBSTATION IED
219