A Novel Web based Expert System Architecture for On-line and

Off-line Fault Diagnosis and Control (FDC) of Transformers

by

Babita Jain. M, M.B Srinivas, Amit Jain

in

TENCON 2008 - 2008, TENCON 2008. IEEE Region 10 Conference 19-21 Nov. 2008 Page(s):1 to 5, DigitalObject Identifier 10.1109/TENCON.2008.4766606

Report No: IIIT/TR/2009/57

Centre for Power SystemsInternational Institute of Information Technology

Hyderabad - 500 032, INDIAMarch 2009

A Novel Web based Expert System Architecturefor On-line and Off-line Fault Diagnosis and

Control (FDC) of Transformers

M. Babita Jain, Member, IEEE, M.B.Srinivas, Member, IEEE, Amit Jain, Member, IEEE

Abstract-- The paper presents the structure and usage mode foran integrated fault-diagnosis and control system fortransformers. The fault diagnosis and control system allows on­line analysis on a desktop application, a web application and off­line analysis for determining the transformer faults and remediesbased on certain symptoms observed on the equipment and theircomparison with the survey results of Cooling system condition,Bushing condition, Insulation system condition, Partial dischargeevolution, Transformer switching in/switching off, exceeding ofmonitored parameter limits and estimation of remained life, thedata of which is continuously updated into the database of theexisting system.

The proposed FDC system uses a Web based Expert SystemArchitecture which has been proven as an effective platform fordiagnostic and control applications of transformers.Conventional expert systems [1] are PC based and are not ofmuch use where the expertise is required over a large network.The advent of the internet has strongly influenced modern powersystems. A web based expert system [2] with knowledge base anddatabase connectivity is a novel architecture and is an aptsolution for both on-line and off-line applications. The purpose ofthis work is to develop a web based expert system shell and thenuse it for the fault diagnosis and control (FDC) [3] oftransformers either off-line (on a stand alone system) or on-linethrough the internet with the facility of on-line up gradation ofdata related to periodic monitoring and maintenance oftransformers.

The proposed system goes beyond imitation of expert­operators' knowledge, being able to inference fault scenariosusing both knowledge base and database of the requiredequipment with no limitation to the number of pieces ofequipment being handled. It is easier, flexible, and more userfriendly. It can be used for both stand-alone (off-line) and Web­based (on-line) applications.

M. Babita Jain is PhD student at Power Systems Research Center,International Institute of Information Technology, Hyderabad, AndhraPradesh, India (e-mail: babita.j2000@yahoo.com).

Dr M B Srinivas, Associate Professor, Head, VLSI & Embedded Systemsat International Institute of Information Technology, Hyderabad, AndhraPradesh, India (e-mail: srinivas@iiit.ac.in).

Dr Amit Jain, Research Assistant Professor, Head, Power SystemsResearch Center at International Institute of Information Technology,Hyderabad, Andhra Pradesh, India (e-mail: amit@iiit.ac.in).

Index Terms- Control, Diagnosis, Database, Expert System,Expert System Shell, Fault, Knowledge Base, On-line diagnosis,Transformers, Web based expert system shell.

1. INTRODUCTION

I n operation, the transformers are subjected to combined

stresses (electrical, thermal, mechanical and environmental),finally leading to the decrease of their life and appearance ofsome faults with irreversible evolution. Also taking intoaccount the fact that most transformers are in operation sincemore than 20 years, it results the necessity of fitting out thetransformers with systems for monitoring, diagnosing andcontrol of faults.

For carrying out the monitoring as source of a diagnosis ascorrect as possible, a mode for collecting data on the surveyedprocess, saving and storing them, filtering and verifying andfinally transmitting them to the user is necessary. This callsfor an efficient decision support system capable of handlinglarge volumes of data, converting the data into meaningfulinformation and supplying the appropriate personnel with theright information at the right time, supporting for on-line andoff-line fault diagnosis and control system. This can beachieved through a web based expert system package with itsunique architecture of connectivity to knowledge base as wellas database. The present work is carried on in two phases:

I. Development ofa web based expert system shellwith a graphical user interface and a databaseconnectivity

2. Development of an on-line and off-line faultdiagnosis and control system (FDC) for Transformersusing the web based expert system shell.

II. DEVELOPMENT OF THE WEB BASED EXPERT SYSTEM SHELL

An expert system [5] is a computer program that representsand reasons with knowledge of a specified subject with a viewto solving problem directly or giving advice. The existingexpert system architecture supports only Knowledge base andonly on stand alone systems.

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Fig 1 is the architecture of the developed web based expertsystem shell. The developed shell extends excellent support toknowledge bases as well as databases to multiple users roundthe globe in contrary to the existing expert system architecturewith only single user and limited knowledge basecompatibility. This module deals with the development of aweb based expert system shell. In an environment whereexpert data and knowledge expertise is required but notavailable due to either lack of required personnel or withpersonnel not having required expertise in diverse fields duelarge size of data, a package developed using the web basedexpert system shell would be a fit of the tool to the problem.

userl user

Fig. 1. Architecture of Web Based Expert System Shell

A. Functional DesignThe development of the web based expert system shellinvolves:1. Knowledge Base Design2. Database Design3. Development of an inference engine4. Development of a graphical user interface

This expert system structure helps in refining theinformation from raw data to the one supporting a particular

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application like fault diagnosis or condition monitoring orpreventive maintenance or any other area where extensivedata is available and assimilation of data or extracting usefulinformation or knowledge from the data is difficult. It is a rulebased web expert system shell developed using .NETtechnology coupled with the inherent property of storing datain text files and database tables. The architecture allows easyaddition of new knowledge bases and databases of theapplication. From the beginning the web based expert systemshell has been designed with extensibility and scalability asthe major criterion.

B. Design Details

1. Knowledge Base:

The knowledge base of the expert system shell stores theextensive knowledge gathered from experts, historical dataand books regarding the application in the form of rules. Theknowledge can be either factual or heuristic. The knowledge isstored in the form of production rules, which contain if-elserules. The knowledge base is divided into three major sectionsnamely: variable section, rules section and asks section. Thevariables section is used to declare all the variables used in theknowledge base, the rules section is used to define all the rulesused to represent the knowledge and the asks section includesall the questions and options for the user to select andcontinue with the consultation for getting the requiredassistance from the expert system. The Fig 3 shows the typicalformat of the knowledge base required for the expert system.

tEas:11II. • •. ~" I' I' •• 1, •••

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Fig. 2. Format of Knowledge Base of Web Based Expert System Shell

2. Database Design:

The information gathered is either factual, heuristic or querybased. Of the data gathered, the data which can be put in theform of a question and answer are put in the database of theapplication. The database table of the expert system shell hasthree fields namely: the id, question and answer. The databasecan be accessed by entering the keyword related to theinformation seeked. This leads to displaying of all thequestions containing the keyword and selection of anyone ofthe questions would provide for the displaying of the requiredinformation.

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3. Inference Engine:

It provides the system COfttrol. It applies the expert domainknowledge to what is known about the present situation todetermine new information about the domain. The inferenceengine is the mechanism that connects the user input in theform of answers to the questions to the rules of knowledgebase and further continues the session to come to conclusions.This process leads to the solution of the problem. Theinference engine also enables the expert system's interface todata sources and to the user. The inference engine alsosupports to identify the rules of the knowledge base used toget decision support from the system and also forms thedecision tree. The inference engine is developed usingVB.NET and it is a DLL (Dynamic Linking Library) file.

4. Graphical User Interface:The graphical user interface of the developed web based

expert system shell comprises of:I. Input interfaceII. User interface andIII. Working memory

I. Input Interface: The input interface to the package isthrough the admin page of the GUI. This allows the expertiseto be uploaded as the knowledgebase files in text format andalso allows updating the database tables for given equipmentby the expert or the knowledge engineer who would act as theadministrator for the given package. The interface also allowsuploading the images of the equipment into the database tohelp in presenting an easy user interface. The input interfacehas been developed using C#.NET and MS Access has beenused to store information in database tables. The advantage ofAccess over SQL and other database servers is its ease ofimplementation while hosting the package on web.

II. User Interface: The user interface to the package isthrough user page of the GUI. This allows for creation of newusers and also allows the existing user to consult the expertsystem in a user friendly manner for decision support. Theuser can select between the database and knowledge base andcan use the database with a very convenient search enginemechanism and the knowledge-base in the form of questionsand answers. The user interface has been developed using theC#.NET technology.

III. Working Memory: The working memory contains theinformation that the system has received about a problem athand. In addition, any information the expert system derivesabout the problem is also stored in the working memory.

III. DEVELOPMENT OF AN ON-LINE AND OFF-LINE FAULTDIAGNOSIS AND CONTROL (FDC) SYSTEM FOR TRANSFORMERS

The developed web based expert system shell is now usedfor the development of an on-line and off-line FDC system.Expert system to be used for fault diagnosis and control calls

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for a deep knowledge base. This is possible by extensive datacollection by the knowledge engineer from the experts in thefield, historical data of fault occurrences and from booksrelated to the field. Lot of data is also obtained from thesurvey results of Cooling system condition, Bushingcondition, Insulation system condition, Partial dischargeevolution, Transformer switching in/switching off, exceedingof monitored parameter limits done at regular intervals. Thedata thus obtained i& put in the form of either if-then rules inthe knowledge base or in the form of question and answer inthe database table, whichever format the data suits to. Theexpert in the particular domain should have extreme expertisein his field and preferably should be an "operationalengineer".

The knowledge base designed for this application of faultdiagnosis and control of Transformers [4] deals with thesymptoms, causes and remedies of various faults frequentlyoccurring in different types of Transformers and thespecifications and standard ratings of the equipment and alsosupports on-line data up gradation supporting for controllingfaults. The data was collected from an electrical factory inVisakhapatnam, India. It is the data about equipment fault, itsdiagnosis and remedial measures and the database comprisingof data from survey results. All the data collected was first putin tabular form for various types of AC Motors withequipment name, symptoms, causes and remedial measures ascolumns. Further they were transformed into decision treesand then as rules in the knowledge base of the expert systempackage.

Let us consider a few fault clearance scenarios using thepresent FDC System.

Based on the visual observations and information receivedfrom the sensors fitted to the transformer, the operator caneasily detect the overheat on magnetic coil in the equipmenti.e. more than the prescribed value (the prescribed value canbe known from the application database); the operator can usethe system and select for the transformer and symptom hightemperature rise. This in tum leads the package seekinformation about the type of the transformer which can beknown from the application database. The inference engineworks on the input in relation with the knowledge base andfinally displays the solution for clearing the fault or problemas reducing load and increasing power factor.

In this way any fault related to various transformers can bevery easily cleared with the assistance of the Fault Diagnosisand Control (FDC) system. Extensive data has been collectedfor power transformers, distribution transformers of all typesfrom the experts, books, historical data and regular on-sitesurvey and stored in the knowledge base and database of thepackage. The data is first transformed in the form of tables,decision trees and then as knowledge base rules and databasequeries for Transformer.

The developed package can always be upgraded with newequipments very easily as extensibility is the main feature ofour web based expert system package. The web based expertsystem package (FDC) developed can be hosted on web and

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Periodicals:

V. REFERENCES

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IV. CONCLUSIONS

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~ .~~. • 'I'" , - ..~,.. . .

Fig. 4. Snapshot2 of the developed FDC System

The design and development of a web based expert systemshell and its role in developing an on-line and off-line FaultOiagnosis and Control (FOC) system for all types ofTransformers is presented in this paper. A brief description ofexpert system architecture [5] and issues involved indeveloping a web based expert system shell and thetechnology used is discussed. The concept of designing a webbased expert system with a user friendly GUI is alsodiscussed.

The application of the shell to develop the package FOCsystem for fault diagnosis and control of Transformers whichprovides on-line and off-line help for diagnosing faults ofvarious kinds of Transformers with various ratings andspecifications and clearing them is discussed in detail in thepaper. The package deals with data collected from an electricalfactory in Visakhapatnam for power transformers, distributiontransformers and various other type of transformers. Thepackage can be easily extended to other equipments also.

The package FOC system for Transformers is developed onthe basis of expert's past experiences in fault clearance and theregular up gradation of data obtained from on-line survey.Thus it renders a cost-effective solution in clearing a fault thatmay occur again. The system can be used on a stand alonesystem and hence work off-line where the on-line connectivityis not possible and as it is a web based application anybodyfrom anywhere can use it for fault diagnosis and controlprovided he is in the network. The package is very userfriendly and is easily extensible.

can be supported on both internet and intranet. Hence the usercan use the package from anywhere round the globe. It is veryuser friendly. It starts with the login page asking for user idand password and also allowing for the registration of a newuser. The login page connects the user to the main pagedisplaying the equipment to be selected. This is a dynamicpage which updates the images and list of equipments to theuser as and when uploaded by the administrator. A click onthe image of the required equipment redirects the user to therespective equipment page with options to select for either theknowledge base or the database of the selected equipment. Onselecting the knowledge base the user enters into a questionand answer session where the user selects for the symptomsbased on the physical observations made for the fault. Thesession ends up finally providing the user with the remedy forthe occurred fault. On selecting for the database the user isprovided with a search engine mechanism where the user canget the details of the equipment specifications, ratings andother details by typing the keyword related to the requirementand the package places all the related data from the equipmentdatabase. The package gives complete freedom to the user toswitch over from one equipment to other and to switch fromthe knowledge base and the database. The login with theadministrator id and password links to the admin page whereuploading of new knowledge bases and updating of existingdatabases can be easily done.

The package once hosted on web for internet services or onlocal host for intranet services is completely available to theclient (user) without any restrictions on the availability of thebuilding technology on the client system. The user can alwaysuse the package in any web browsers like IE5 or Mozilla. etc.as the package is totally user friendly the user is not requiredto know any technology to work with the package and use itfor fault diagnosis and control except for typing the URL toget to the login page.

Snapshots of the developed on-line and off-line FOC Systemfor Transformers are given below:. . .._~ ~.- ~ ~~~ .::~:-·H..~;~.·~=~ l'-••-., _-

Fig. 3. Snapshot1 of the developed FDC System

[1] A Moyes, J R Mcdonald, "The Use of Intelligent Systems Techniques inCondition1 Monitomng of Electrical Plant" Q3 1997 The Institution Of

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Electrical Engineers, Printed and Published By The lee, Savoy Place,London Wcpr ObI, Uk

[2] "Incorporating Expert Systems into web based environment" fromproceeding (385) Artificial Intelligence and Soft computing-2003

[3] C. Han and S. Gerasenko (USA) AM. D. Judd, S. D. J. Mcarthur,"Intelligent Condition Monitoring and Asset Management PartialDischarge Monitoring For Power Transformers", Power EngineeringJournal December 2002

Papers from Conference Proceedings (Published):

[4] Miine,R, "Fault Diagnosis & Expert Systems", The 6lh InternationalWorkshop On Expert Systems And Their Applications. Avington,France

[5] K.S, Swamp and H. S. Chandrasekharaiah, "Diagnostic ReasoningBased On Structure and Behavior", Conference: Power System 2000

VI. BIOGRAPHIES

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M Babita Jain is PhD student at the InternationalInstitute of Information Technology, Hyderabad, Indiasince 2006. The areas of interest include ITApplications to Power Systems, Multi Agent Systems.She has actively involved in establishing IEEE studentbranch and Women in engineering affinity groupactivities.

M B. Srinivas is Associate Professor at theInternational Institute of Information Technology,Hyderabad, India where he is also heading center forVLSI and Embedded systems. He is a very activeIEEE member and presently he is Chairman of IEEEHyderabad section.

Amit Jain graduated from KNIT, India inElectrical Engineering. He completed his masters andPh.D. from Indian Institute of Technology, NewDelhi, India.He was working in Alstom on the power SCADAsystems. He was working in Korea in 2002 as a Post­doctoral researcher in the Brain Korea 21 project teamof Chungbuk National University. He was PostDoctoral Fellow of the Japan Society for the

Promotion of Science (JSPS) at Tohoku University, Sendai, Japan. He alsoworked as a Post Doctoral Research Associate at Tohoku University, Sendai,Japan. Currently he is an Assistant Professor in lIlT, Hyderabad, India. Hisfields of research interest are power system real time monitoring and control,artificial intelligence applications, power system economics and electricitymarkets, renewable energy, reliability analysis, GIS applications, parallelprocessing and nanotechnology.

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