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

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

Off-line Fault Diagnosis and Control (FDC) of Power System

Equipment

by

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

in

Power System Technology and IEEE Power India Conference, 2008. POWERCON 2008. Joint InternationalConference on 12-15 Oct. 2008,Pages:1 to 5,Digital Object Identifier 10.1109/ICPST.2008.4745378

Report No: IIIT/TR/2009/40

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 Power System Equipment

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

Abstract-- The paper presents the structure and usage modefor an integrated fault-diagnosis and control system for powersystem equipment. The fault diagnosis and control system allowson-line analysis on a desktop application, a web application andoff-line analysis for determining the transformer faults andremedies based on certain symptoms observed on the equipmentand their comparison with the survey results of Cooling systemcondition, Bushing condition, Insulation system condition, Partialdischarge evolution, Transformer switching in/switching off,exceeding of monitored parameter limits and estimation ofremained life, the data of which is continuously updated into thedatabase of the existing system. Such modules are developed forac motors, dc motors, and street lamps and are integrated in onepackage namely Fault Diagnosis and Control (FDC) 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 of powersystem equipment.

The proposed system goes beyond imitation of expert-operators' 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 user

M. Babita Jain is PhD student at Power Systems Research Center,International Institute of Information Technology, Hyderabad, AndhraPradesh, India (e-mail: babitaJ2000gyahoo.com).M B Srinivas, Associate Professor, VLSI & Embedded Systems at

International Institute of Information Technology, Hyderabad, AndhraPradesh, India (e-mail: [email protected]).

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

friendly. It can be used for both stand-alone (off-line) and Web-based (on-line) applications.

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

I. INTRODUCTION

IN operation, the power system equipment are subjected tocombined stresses (electrical, thermal, mechanical andenvironmental), finally leading to the decrease of their life

and appearance of some faults with irreversible evolution.Also taking into account the fact that most of the powersystem equipment are in operation since more than 20 years, itresults the necessity of fitting out the transformers withsystems for monitoring, diagnosing and control 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:

1. Development of a 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 powersystem equipment using the web based expert systemshell.

II. WEB BASED EXPERT SYSTEM SHELL DEVELOPMENT

A computer program that represents and reasons withknowledge of a specified subject with a view to solvingproblem directly or giving advice and try to mimic humanbehavior for solving a problem is an Expert System inComputer paradigm [5]. The existing expert system

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architecture supports only Knowledge base and only on standalone systems.

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.

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usiluser user3 u;s Asiserx usery ADMNuen

Fig. 1. Architecture of Web Based Expert System Shell.

A. Functional Design of Web Based Expert System ShellThe development of the web based expert system shell

involves:1. Knowledge Base Design2. Database Design3. Development of an inference engine4. Development of a graphical user interface

This expert system structure helps in refining the

information from raw data to the one supporting a particularapplication 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. Web Based Expert System Shell Design Details

1. Knowledge Base:The basic idea involved in the design of the knowledge

base of the expert system shell is that it stores the extensiveknowledge gathered from experts, historical data and booksregarding the application in the form of rules. The knowledgecan be either factual or heuristic. The knowledge is stored inthe form of production rules, which contain if-else rules. Theknowledge base is divided into three major sections namely:variable section, rules section and asks section. The variablessection 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 2 shows the typicalformat of the knowledge base required for the expert system.

2. Database Design:The data base stores the information gathered which is

either factual, heuristic or query based. Of the data gathered,the data which can be put in the form of a question and answerare put in the database of the application. The database tableof the expert system shell has three fields namely: the id,question and answer. The database can be accessed byentering the keyword related to the information seeked. Thisleads to displaying of all the questions containing the keywordand selection of any one of the questions would provide forthe displaying of the required information.

3. Inference Engine:The entire control and operation of the system is done by

the inference engine. It applies the expert domain knowledgeto what is known about the present situation to determine newinformation about the domain. The inference engine is themechanism that connects the user input in the form of answersto the questions to the rules of knowledge base and furthercontinues the session to come to conclusions. This processleads to the solution of the problem. The inference engine alsoenables the expert system's interface to data sources and to theuser. The inference engine also supports to identify the rulesof the knowledge base used to get decision support from thesystem and also forms the decision tree. The inference engineis developed using VB.NET and it is a DLL (Dynamic


Linking Library) file.

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very convenient search engine mechanism and the knowledge-base in the form of questions and answers. The user interfacehas been developed using the C#.NET technology.

iii. Working Memory of the web based expert system shell:The working memory contains the information that the systemhas received about a problem at hand. In addition, anyinformation the expert system derives about the problem isalso stored in the working memory.

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

4. Graphical User Interface (GUI):The developed graphical user interface (GUI) of the web

based expert system shell comprises of:i. Input interfaceii. User interface andiii. Working memory

i. Input Interface of the web based expert system shell: Theinput interface to the package is through the admin page of theGUI. This allows the expertise to be uploaded as theknowledgebase files in text format and also allows updatingthe database tables for given equipment by the expert or theknowledge engineer who would act as the administrator forthe given package. The interface also allows uploading theimages of the equipment into the database to help inpresenting an easy user interface. The input interface has beendeveloped using C#.NET and MS Access has been used tostore information in database tables. The advantage of Accessover SQL and other database servers is its ease ofimplementation while hosting the package on web.

ii. User Interface of the web based expert system shell: Theuser interface to the package is through user page of the GUI.This allows for creation of new users and also allows theexisting user to consult the expert system in a user friendlymanner for decision support. The user can select between thedatabase and knowledge base and can use the database with a

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

EQUIPMENT

The web based expert system shell developed is now usedfor the development of an on-line and off-line FDC system.The package is explained in the paper for Transformer and thesame procedure has been followed for the development of theother equipment modules. Finally all the modules have beenintegrated as the FDC System for the power systemequipment. Expert system to be used for fault diagnosis andcontrol calls for a deep knowledge base. This is possible byextensive data collection by the knowledge engineer from theexperts in the field, historical data of fault occurrences andfrom books related to the field. Lot of data is also obtainedfrom the survey 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 is 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 fault

diagnosis 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 Transformers 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 overheat on magnetic coil in the equipment i.e.more than the prescribed value (the prescribed value can beknown from the application database); the operator can use

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the system and select for the transformer and symptom hightemperature rise. This in turn 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 includes all the power system

equipment like acmotors, dcmotors, transformers, andstreetlamps and can always be very easily upgraded with anyother equipment. Extensibility is the main feature of our webbased expert system package. The web based expert systempackage (FDC) developed can be hosted on web and can besupported on both internet and intranet. Hence the user canuse 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 on

local 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 to

get to the login page.Snapshot of the developed on-line and off-line FDC System

for Power System Equipment is given below:

Fig. 3. Snapshot2 of the developed FDC System.

IV. CONCLUSIONS

The paper presents an overview of the work involved in thedevelopment of a web based expert system shell. It deals indetail with the architecture of an expert system [5] and alsodescribes the developments made to the architecture so that itserves to be a web based expert system shell. The paperthrows light on the aspect of applications of a web basedexpert system shell. A user friendly GUI has been developedwhich acts as a interface between the web based expert systemand the user. The aspects of using the web based expertsystem shell for the area of fault diagnosis of power systemequipment have been dealt in detail. Hence an on-line and off-line Fault Diagnosis and Control (FDC) system for all PowerSystem Equipment has been presented in this paper.The data required for the implementation of the on-line and

off-line FDC system has been collected from an electricalfactory. The data thus collected includes the ratings of variousequipments, their earlier fault record histories, specificationsand the history data of the methods implemented in clearingthe faults. All the issues of knowledge gathering for the expertsystem have been dealt in detail in the paper.The package FDC system for power system equipment is

developed on the basis of expert's past experiences in faultclearance and the regular up gradation of data obtained fromon-line survey. Thus it renders a cost-effective solution inclearing a fault that may occur again. The system can be usedon a stand alone system and hence work off-line where the on-line connectivity is not possible and as it is a web basedapplication anybody from anywhere can use it for faultdiagnosis and control provided he is in the network. Thepackage is very user friendly and is easily extensible.


V. REFERENCES

[1] A Moyes, J R Mcdonald, "The Use of Intelligent Systems Techniques inConditionl Monitomng of Electrical Plant" Q3 1997 The Institution OfElectrical Engineers, Printed and Published By The lee, Savoy Place,London Wcpr Obl, 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

[4] Miine,R, "Fault Diagnosis & Expert Systems", The 61h InternationalWorkshop On Expert Systems And Their Applications. Avington,France

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

VI. BIOGRAPHIESM Babita Jain is PhD student at the International

Institute 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 working in the centerfr VLSI and Embedded systems.

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 powerSCADA systems. He was working in Korea in 2002as a Post-doctoral researcher in the Brain Korea 21project team of Chungbuk National University. Hewas Post Doctoral Fellow of the Japan Society for thePromotion of Science (JSPS) at Tohoku University,

Sendai, Japan. He also worked as a Post Doctoral Research Associate atTohoku University, Sendai, Japan. Currently he is an Assistant Professor inIIIT, Hyderabad, India. His fields of research interest are power system realtime monitoring and control, artificial intelligence applications, power systemeconomics and electricity markets, renewable energy, reliability analysis, GISapplications, parallel processing and nanotechnology.


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