Application System

Fault Analysis Based on Integration of

Digital Relay and DFR Data

X. Luo, Student Member, IEEE, and M. Kezunovic, Fellow, IEEE

internal behavior of relays, are recorded [7]. The data are

usually contained in various relay files and reports such as

Abstract This paper discusses integration of two existing

automated analysis applications, DFR Data Analysis and Digital oscillography file, setting file, fault report and event report.

Relay Data Analysis, to achieve comprehensive fault analysis. As Recently, an expert system based Digital Protective Relay Data

inputs to the integrated application, digital relay files and reports

Analysis (DPRDA) application has been developed to perform

are introduced. The proposed strategy and implementation of

validation and diagnosis of digital relay operation in great detail

integration are outlined. An example is used to demonstrate

by analyzing relay files and reports [8]. The analysis is partially

features of the integrated application developed so far.

based on disturbance information provided by a disturbance

Index Terms digital relay, IED, expert system, fault analysis,

data integration event analysis function, which is not included in the DPRDA

application currently.

I. INTRODUCTION Based on evaluation of DFRDA and DPRDA applications, a

T HE history of automated fault analysis dates back to the late strategy of combining the two applications to perform

eighties when first expert systems for automated analysis comprehensive fault analysis based on relay files and reports are

were introduced [1]. In the last two decades, various expert proposed in this paper. Section II introduces files and reports of

system applications for fault analysis have been reported in modern digital relays, which provide fundamental information

literature [2], [3], [4]. Most of these applications rely on rule for fault analysis. Section III details the strategy of fault analysis

based expert system techniques to perform disturbance analysis based on integration of the two applications. Then Section IV

and validation of protection system operation using sequence of discusses implementation issues of integration. Section V

events recorders (SER), digital fault recorders (DFR) and presents an example to illustrate features of the integrated

supervisory control and data acquisition (SCADA) systems as application developed so far. Finally, conclusions and proposals

sources of relevant field data. for future work are given in Section VI.

Reference [5] presents an expert system based DFR Data

Analysis (DFRDA) application for automated fault analysis. In II. FILES AND REPORTS OF DIGITAL RELAYS

this application, analog waveforms as well as statuses of relay Modern digital relays are capable of generating various files

and circuit breaker contacts recorded by DFRs are used to and reports, each of which may address a specific purpose.

analyze disturbance events and protection system operation. Generally, an oscillography file records what a relay sees

Evaluation and test carried out at Center Point Energy Company during disturbance events. A setting file specifies how the relay

in Houston proves that this application is quite successful [6]. is configured. A fault report presents parameters calculated by

However, only limited behavior of protection systems is the relay for its decision making. An event report reveals how

analyzed in this application. This is due to the fact that DFRs the relay actually responds to the disturbance events according

can not provide detailed information of internal states of to its decision. It is also worth mentioning that in order to

protection system components, especially relays. achieve maximum flexibility, the firmware of many digital

Due to the power of microprocessors, many modern digital relays is designed as functions by employing Object-Oriented

protective relays can provide users with abundant data about Design and Programming techniques. These functions usually

what relays see and how they respond during power system are input and output contacts, protection elements, control

faults. These data include not only sampled analog currents and elements and pilot schemes. In relay files and reports, the states

voltages but also status of input and output contacts, which are of each function are represented by a set of predefined logic

acquired by fault recording function. Also, statuses of operands [9], [10]. Four common relay files and reports are

protection elements and logic operands, which reveal detailed introduced as follows.

A. Oscillography File

This work was supported by PSerc Project T-17 Enhanced Reliability of

An oscillography file is usually in COMTRADE format [11].

Power System Operation Using Advanced Algorithms and IEDs for On-Line

Monitoring . It is generated by the fault recording function of a digital relay.

X. Luo and M. Kezunovic are with the Department of Electrical Engineering,

Nowadays the fault recording function of many digital relays is

Texas A&M University, College Station, TX 77843-3128, USA (e-mails:

quite powerful. For example, GE s D60 relay can record up to

*****@**.****.***, *******@**.****.***)

16 analog channels and 64 digital channels at a sampling rate of

64 samples per cycle. The data in several oscillography files can III. STRATEGY OF FAULT ANALYSIS BASED ON INTEGRATION

be concatenated to achieve even longer recording time [9].

A. Conceptual Strategy of Integration

Since the recording capability of many digital relays is

comparable to that of specialized DFRs, applying the The underlying idea of integration of DFRDA and DPRDA

algorithms of DFRDA application on the oscillography data of a applications is that the algorithms for DFRDA application are

digital relay is feasible and justifiable. used to perform detailed disturbance event analysis based on the

It should also be mentioned that an advantage of fault data in COMTRADE oscillography file generated by fault

recording function of a digital relay over a DFR is that the status recording function of a relay, while the algorithms for DPRDA

of any logic operand can be recorded as a digital channel. That application are taken to perform detailed validation and

is to say, status of both external contacts and internal states of a diagnosis of relay operation based on the results of disturbance

digital relay can be recorded in its oscillography file while the

event analysis and the data from all the relay files and reports.

digital channels of a DFR can only record the status of external

Fig. 1 illustrates the conceptual strategy of integration.

contacts.

As introduced in Section I, DFRDA application can perform

B. Setting File detailed disturbance analysis [5]. The disturbance information

provided by the original DFRDA application includes fault

A setting file contains configuration information of a relay.

detection, fault inception time, fault type, circuit breaker current

Usually a setting file configures the relay at three levels:

selecting protection and control elements, deciding how the interruption detection and circuit breaker current interruption

selected elements are logically combined and setting operating time. A new fault location algorithm based on synchronized

parameters of each selected element. The three levels of sampling at two ends of lines has been adopted during the later

information are used in DPRDA application to determine the improvements [13]. Since only a few external contact signals

expected relay behavior. such as relay trip signal, communication signal and circuit

breaker contact signal are recorded by DFRs, the DFRDA

C. Fault Report

application only performs simple analysis of protection system

A fault report usually contains information of fault type, fault

operation.

location and voltage and current phasors during pre-fault and

On the other hand, DPRDA application can perform detailed

fault periods. The information is provided by the relay itself.

analysis of protection system operation because its analysis is

Whether the fault type and fault location information produced

based on abundant data, which reflect both the external contact

by a relay can be used to verify protection operation of the relay

status of a relay and its associated circuit breaker and the

itself depends on two preconditions. First, the fault

internal element status of the relay [8]. The analysis results not

classification and fault location algorithms of the relay should

only include validation of correctness of phase operation, relay

be independent from its protection algorithms. Otherwise it is

trip operation, circuit breaker opening and circuit breaker

unreasonable to use the result of one of two related algorithms

current interruption, but also include the reasons for certain

as reference to verify the result of the other. Secondly, the fault

failure and missoperation. A deficiency of the current DPRDA

classification and fault location algorithms should be accurate

application is that its analysis needs external disturbance

enough. If the two preconditions can t be satisfied, an external

information.

source of disturbance information based on advanced

As we can see, the DFRDA application and DPRDA

algorithms and techniques should be used instead of the

application are actually complementary to each other and their

information provided by the relay [5], [12], [13]. In discussion

integration may overcome their individual deficiencies and

of this paper, the DFRDA application serves as the external

result in a comprehensive fault analysis application.

source of information.

D. Event Report

An event report is a list of time-stamped logic operands in

chronological order. It contains most of the information through

which the external operation and internal states of a digital relay

can be observed. According to our investigation, for some types

of relays, not all active logic operands that may be important for

analysis are reflected in the event reports. This problem can be

solved if users select these operands to be recorded in the

oscillography file of the relay.

It should be noticed that relay performance specification in

user s manuals also provides useful information of elements

operating parameters for predicting relay behavior. For example,

a performance specification for a phase distance element may be

its average operating time for Zone 1.

Fig. 1. Conceptual strategy of integration of two applications

B. Modules of the Integrated Application

The integration application is composed of several modules

which come from DFRDA and DPRDA applications. As shown

in Fig.2, DFRDA application consists of Signal Processing

Module, Event Analysis Expert System Module and Fault

Location Module. Fig. 3 shows that DPRDA application

includes Relay Operation Logic Expert System Module and

Validation and Diagnosis Expert System Module.

Signal Processing Module takes oscillography data contained

in a COMTRADE file of the relay. It first distinguishes the

pre-fault, fault, and post-fault time intervals of voltages and

currents. Then the RMS values of voltages and currents as well

as the zero sequence values of currents for the three time

intervals are calculated. During the calculation, the fault

inception time and circuit breaker current interruption time may

be decided.

The Event Analysis Expert System Module takes the signal

parameters extracted from the Signal Processing Module as

inputs. It performs forward chaining reasoning to analyze the

relationship of RMS values of voltages and currents to detect

the fault and classify the fault type. It also uses the values of zero Fig. 3. Functional modules of DPRDA application

sequence currents and fault detection information to detect

validation of correctness of relay operation based on

current interruption by the circuit breaker.

hypothesis-fact matching, and then the diagnosis of the reasons

Fault Location Module uses oscillography data from

for certain failure and missoperation is obtained using

COMTRADE files of both the local relay and the remote relay

backward chaining reasoning [14]. Finally a report on the

to calculate fault location based on synchronized sampling

results of validation and diagnosis will be generated.

technique.

As discussed above, comprehensive fault analysis is achieved

Based on the analysis results from modules of DFRDA

by the integrated application. The analysis results, which

application, a disturbance report will be generated. It generally

include detailed information of both power system disturbance

includes disturbance information such as fault inception time,

and protection system operation, can serve different user groups.

fault location, fault type, circuit breaker current interruption

System operators may conduct system restoration after faults

time.

based on the disturbance information. Protection engineers may

The disturbance information, along with data in the relay

setting file and performance specification, is taken into Relay use the validation and diagnosis information of protection

Operation Logic Expert System Module to predict status and system operation to evaluate performance, identify component

timing of each active logic operand of the relay by performing deficiencies and trace possible reasons for black outs.

forward chaining reasoning.

The actual status and timing of logic operands are obtained IV. IMPLEMENTATION OF THE INTEGRATION

from the event report and the digital portion of osillography file.

As discussed in Section II, both DFRDA and DPRDA

With both hypothesis and facts of relay behavior as inputs,

applications are developed using modular concept by

Validation and Diagnosis Expert System Module first performs

employing Object-Oriented techniques. An efficient way to

integrate the two applications is to embed the modules of one

application into the other. Our proposed approach is to embed

the modules of DFRDA application into DPRDA application.

A. Implementation Architecture

The framework of DPRDA application is developed under

the platform of Visual C++. The CLIPS expert system inference

engine is linked with the framework by means of Dynamic Link

Library (DLL). The framework mainly takes care of loading

facts and rules into the inference engine and reading the

inference results from the engine.

Since the Event Analysis Expert System Module of DFRDA

application is also developed in CLIPS expert system shell [14],

Fig. 2. Functional modules of DFRDA application

it can directly use the inference engine in DPRDA application.

The Signal Processing Module and Fault Location Module of V. EXAMPLE

DFRDA application are originally developed using MATLAB In this section we use an example to demonstrate some

M-file programming language, which makes it difficult to features of the proposed integrated application. Since currently

directly link them with the framework of DPRDA application. the integration of modules of DFRDA application into DPRDA

To solve the problem, a convenient way is to use the MATLAB application has not yet been completed, we will make

C Code Generation Toolbox to convert the M-file Codes into C assumptions about the outputs of Signal Processing Module,

code and make the two modules as Dynamic Link Library (DLL) Fault Location Module and Event Analysis Expert System

Module, then use a modified graphic user interface (GUI) of

to link with the framework of DPRDA application. Fig. 4

DPRDA application to demonstrate the example.

illustrates the implementation structure of the integrated

application. A. Simulation Procedure

B. Program Execution Process We first set up simulation in a laboratory to get the relay

reports and files to be analyzed, which is shown in Fig. 5.

In Fig.4, the application framework serves as an interface for

ATP program is used to simulate the disturbance event. Then

all the functional modules as well as inputs and outputs of the

a commercial software called RELAY ASSISTANT is used to

application. It first reads in oscillography data from the

convert the ATP data file in PL4 format into COMTRADE

COMTRADE file and calls Fault Location DLL and Signal

format and download it to the relay test set [15]. The simulated

Processing DLL to process these data. The processing results

signals are generated by the relay test set and input to the relay

are sent back to the framework. Then CLIPS Inference Engine

to be tested. This triggers the relay to operate and generate files

DLL is called and results from Signal Processing DLL together

and reports. These reports and files are automatically read into

with event analysis rules are loaded into the CLIPS Inference

the fault analysis application.

Engine. The inference results for event analysis along with fault It should be mentioned that the contact signal of circuit

location result and some signal processing results constitute breaker associated with the relay is simulated using a logic

disturbance information. At this point, the framework further operand signal and a timer inside the relay. The timing of the

reads in relevant data from relay setting file and performance contact signal is set to match the event simulated in ATP

specification. After CLIPS Inference Engine DLL is called program.

again, these data and disturbance information together with

B. Relay Files and Reports

relay operation logic rules are loaded into CLIPS Inference

The disturbance event is caused by an A-B-G fault. Fig. 6

Engine to predict relay behavior. Finally, the framework reads

shows the oscillography file displayed in the GUI of DPRDA

in data which represent actual relay behavior from the event

application. TABLE I is the list of disturbance information

report and the digital portion of COMTRADE file and loads

which is set as the simulation parameters in ATP program.

them into CLIPS Inference Engine together with validation and

It should be noticed that in this example we assume that the

diagnosis rules. The inference results are information of

modules of DFRDA application has generated the same

validation and diagnosis of protection system operation.

disturbance information as listed in TABLE I so that DPRDA

application can directly use the information.

RELAY

Relay Reports

ATP ASSISTANT Relay Test Set Relay And Files

Software

Fig. 5. Simulation procedure to get relay files and reports

Fig.4. Implementation architecture of the integrated application for

comprehensive fault analysis

Fig. 6. Oscillography file

TABLE I When performing analysis, the absolute time for each logic

DISTURBANCE INFORMATION

operand in the event report is converted to relative time with

respect to the fault inception time.

Fault Type A-B-G

Fault Location Zone 2

C. Results of Validation and Diagnosis

Fault Inception Time 0.18 second

The results are displayed in the dialog shown in Fig. 9 (a) and

CB Currents Interruption Succeeded

Fig. 9 (b) respectively.

CB Currents Interruption Time 0.764 second

As we can see in the validation information section, PHASE

Corresponding to the fault, the relay and associated circuit IOC Element operated to make the relay trip. The circuit

breaker should behave as expected according to the relay setting breaker opened because of the relay trip and the fault currents

and performance specification. The relay setting file is were interrupted by the circuit breaker.

automatically read into the DPRDA application. The Several failures and misoperation were identified as shown in

performance specification is manually input into a dialog shown the diagnosis information section. Ground Distance Zone 2

in Fig. 7. element and Ground Distance Zone 3 element should have

According to the relay setting and performance specification, picked up but failed to pick up because their neutral current

Phase Distance Zone 2 Element and Ground Distance Zone 2 supervising failed. The neutral current supervising of Ground

Element should operate to make the relay trip at 0.502 second Distance Zone 1 element also failed. In addition, Ground IOC

and the circuit breaker should open at 0.550 second. element failed to pick up. From the diagnosis information for

The actual relay and circuit breaker behavior in terms of status ground elements, we may know that it is highly possible that

and timing of relay logic operands are recorded in the event something is wrong with the neutral current channel.

report. Fig. 8 shows a portion of the report displayed in the GUI Because Phase Distance Zone 2 element should have

of DPRDA application. It should be noticed that we have operated but failed to operate, it was the Phase IOC element

deliberately manipulated the event report to introduce some instead of Phase Distance Zone 2 element that made the relay

failures and missoperation so that the analysis capability of the trip. From such information, we may know that Phase IOC

application can be demonstrated comprehensively. element functioned correctly as a backup for distance elements.

Since the operating time delay of Phase IOC element was set to

be longer than that of Phase Distance Zone 2 element, the relay

trip was delayed. The reason for failure of operation of Phase

Distance Zone 2 was that its CA and AB phase elements picked

up but failed to operate and its BC phase element even failed to

pick up.

Further more, there was timing diagnosis information related

to circuit breaker. The circuit breaker opened a little bit faster

than expected but within pre-set tolerance. However, it

interrupted currents slower than expected. The delay was out of

the pre-set tolerance.

All the validation and diagnosis information is as expected,

which proves the correctness of the design of the application.

Fig. 7. Relay and circuit breaker performance specification dialog

Fig. 9 (a). Validation information

Fig. 8. Event report

[4] D. G. Esp, Real-time fault analysis for transmission systems, Artificial

Intelligence Techniques in Power Systems, IEE Colloquium on, Nov. 3,

1997, pp. 5/1 - 5/4.

[5] M. Kezunovic, P. Spasojevic, C. Fromen, D. Sevcik, An expert system

for transmission substation event analysis, IEEE Trans. Power Delivery,

vol. 8, no. 4, pp. 1942-1949, October 1993.

[6] Kezunovic, I. Rikalo, C. Fromen, Expert system reasoning streamlines

disturbance analysis, IEEE Computer Applications in Power, vol. 7, No.

2, pp. 15-19, April 1994.

[7] D. Costello, Understanding and analyzing event report information,

technical paper, Schweitzer Engineering Laboratories, Inc., Pullman, WA,

2000, Available: http://www.selinc.com/techpprs.htm.

[8] M. Kezunovic, X. Luo, Automated analysis of protective relay data,

18th International Conference on Electricity Distribution CIRED, Turin,

Italy, June 2005.

[9] Instruction Manual for D60 Line Distance Relay, General Electric

Company, Fairfield, CT, 2004.

[10] Instruction Manual for SEL421 High-Speed Line Protection, Automation,

and Control System, Schweitzer Engineering Laboratories, Inc., Pullman,

WA, 2004.

[11] IEEE Common Format for Transient Data Exchange (COMTRADE) for

Power Systems, IEEE Standard, 1999.

[12] S. Vasilic, M. Kezunovic, An improved neural network algorithm for

classifying the transmission line faults, IEEE PES Winter Meeting, New

York, Jan 2002.

[13] M. Kezunovic, B. Perunicic, Automated transmission line fault analysis

using synchronized sampling at two ends, IEEE Trans. Power Systems,

vol. 11, no. 1, pp. 441-447, February 1996.

[14] J. Giarratano, G. Riley, Expert Systems Principles and Programming,

PWS Publishing Company, Boston, 1994, pp. 158-165.

[15] Primer for PC-Based Simulator for Relay Testing, Test Laboratories

International, Inc., College Station, TX, 2002.

[16] M. Kezunovic, Z. Ren, G. Latisko, D.R. Sevcik, J. Lucey, W. Cook, E.

Fig. 9 (b). Diagnosis information Koch, Automated monitoring and analysis of circuit breaker operation,

IEEE Transactions on Power Delivery (Accepted, In Press).

CONCLUSION

VI.

Xu Luo (S 05) received his B.E. and M.E. degrees from Xi an Jiaotong

Based on the discussion in this paper, conclusions are drawn University, Xi an, China, both in electrical engineering in 1999 and 2002

respectively. He has been with Texas A&M University pursuing his Ph.D.

as follows:

degree since Aug. 2002. His research interests are power system protection,

Various reports and files generated by digital protective substation automation and artificial intelligence applications in Power System

relays provide abundant information for comprehensive fault protection.

analysis.

Mladen Kezunovic (S 77, M 80, SM 85, F 99) received his Dipl. Ing. Degree

Expert system is a very promising artificial intelligence from the University of Sarajevo, the M.S. and Ph.D. degrees from the

technique for developing automated analysis applications to University of Kansas, all in electrical engineering, in 1974, 1977 and 1980,

power system. respectively. He has been with Texas A&M University since 1987 where he is

the Eugene E. Webb Professor and Director of Electric Power and Power

Integration of existing fault analysis applications though

Electronics Institute. His main research interests are digital simulators and

data integration and information exchange is an effective way to simulation methods for equipment evaluation and testing as well as application

gain improvements of analysis capability. of intelligent methods to control, protection and power quality monitoring. Dr.

Future work will be related to embedding modules of Kezunovic is a registered professional engineer in Texas, and a Fellow of the

IEEE.

DFRDA application into DPRDA application. Further more,

another existing analysis application based on expert system

technique, the Circuit Breaker Monitoring application [16] may

also be integrated with DFRDA application and DPRDA

application to achieve even more comprehensive fault analysis.

REFERENCES

[1] M. Kezunovic, C.C. Liu, J. McDonald, L.E. Smith, Automated Fault

Analysis, IEEE Tutorial, IEEE PES, 2000.

[2] M. Meri, An expert system for disturbance analysis validation and

verification, Third Symposium on Expert Systems Application to Power

Systems, Tokyo/Kobe, Japan, April 1992.

[3] S. D. J. Macarthur, J. R. McDonald, S. C. Bell, Expert systems and

model based reasoning for protection performance analysis, Artificial

Intelligence Applications in Power Systems, IEE Colloquium on, April

20, 1995.

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