A Web based Expert System Shell for Fault Diagnosis and Control of Power System

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

International Institute of Information Technology, Gachiwbowli, Hyderabad 500032, India

Abstract--Power companies arrange regular training sessions to keep their operators ready to face blackout events, and expert systems play an important role in achieving this goal. Expert systems [1] have been proven to be an effective platform for diagnostic and control applications in power industry. Conventional expert systems are PC based and are not of much use where the expertise is required over a large network. The advent of the internet has strongly influenced modern power systems. A web based expert system [2] is an apt solution for such environments. Existing intranet solutions are being gradually replaced with www services available everywhere and at any time. Originally expert systems have been used for internal purposes in different organizations. The purpose of this work is to develop a web based expert system shell and then use it for the fault diagnosis and control [3] of traditional power system equipment with extensive information and data collected in an electrical factory. The issues of knowledge representation, development of the knowledge base and interface solution have been considered. The proposed solution is based on the pilot implementation of the web based expert system package in a large electrical factory in Visakhapatnam.

This paper aims at developing a web based expert system package with a user friendly graphical user interface and a link to the knowledge base through the expert system shell and a link to the database using the database tools. Further the package has been used to develop an Intelligent Fault Diagnosis and Control Paradigm (IFDCP) capable of dealing with faults on general power system equipment and guide operators for fault diagnosis and control or restoration in general and in the electrical factory considered in particular.

The GUI, Expert System Shell, and the Databases are developed by integrating the standardized technologies, such as C#.NET, ASP.NET, MS Access DB tools and the dynamic linking library (DLL) files. The knowledge base required for the package IFDCP presents extensive data obtained from discussions with experts in different domains of the electrical factory and the past historical data of fault occurrences and their clearance at that factory in the form of simple IF-THEN rules. The package is capable of handling faults on Transformers, DC Motors, AC Motors and Street Lamps. The proposed system goes beyond imitation of expert-operators' knowledge, being able to inference fault scenarios using both knowledge base and database of the required equipment with no limitation to the number of pieces of equipment being handled. It is easier, flexible, and more user friendly. It can be used for both stand-alone and Web-based applications.

Index Terms--Expert Systems, Web based Expert System, Expert System Shell, Knowledge Base, Database, DC Motors,

Transformers, Induction Motors, Condition Monitoring, Diagnosis, Control.

I. Introduction

ithin the power industry, an increasing number of condition monitoring, diagnosis, control and data capture

systems are being deployed throughout the power system. This leads to a number of issues like volume of data to be interpreted being large, data sources being dispersed around the network and plant items, several data sources needed to be integrated and interpreted to provide a true diagnosis of any problem (e.g. SCADA data and digital fault records for power system diagnostics; load data, DGA results, on-line gas analysis results and other monitored values for transformer monitoring) and further addition of data sources in the future for diagnostic condition monitoring thus needing flexibility and extensibility.

Therefore, decision support must be provided for diagnostic and monitoring applications in order to: 1. Handle large volumes of data 2. Convert the data into meaningful information 3. Supply the appropriate personnel with the

right information at the right time. These functions can be achieved through a web based

expert system package with its unique architecture of connectivity to knowledge base as well as database.

The present work is carried on in two phases: 1. Development of a web based expert system shell with a

graphical user interface and a database connectivity 2. Development of an Intelligent Fault Diagnosis [4] and

Control Paradigm (IFDCP) for power system equipment using the web based expert system shell.

II. Development of the web based expert system shell

An expert system [5] is a computer program that represents and reasons with knowledge of a specified subject with a view to solving problem directly or giving advice.

Fig 1 is the architecture of the developed web based expert system shell. The developed shell extends excellent support to knowledge bases as well as databases to multiple users round the globe in contrary to the existing expert system architecture with only single user and limited knowledge base compatibility. This module deals with the development of a

w

2008 International Conference on Condition Monitoring and Diagnosis, Beijing, China, April 21-24, 2008

978-1-4244-1622-6/08/$25.00 ©2007 IEEE

web based expert system shell. In an environment where expert data and knowledge expertise is required but not available due to either lack of required personnel or with personnel not having required expertise in diverse fields due large size of data, a package developed using the web based expert system shell would be a fit of the tool to the problem.

Experts Historical Data Books

user1 user2 user3 userx usery ADMIN usern

Fig 1

A. Functional Design The development of the web based expert system shell involves: 1. Knowledge Base Design 2. Database Design 3. Development of an inference engine 4. Development of a graphical user interface

This expert system structure helps in refining the information from raw data to the one supporting a particular application like fault diagnosis or condition monitoring or preventive maintenance or any other area where extensive data is available and assimilation of data or extracting useful information or knowledge from the data is difficult. It is a rule based web expert system shell developed using .NET technology coupled with the inherent property of storing data in text files and database tables. The architecture allows easy

addition of new knowledge bases and databases of the application. From the beginning the web based expert system shell has been designed with extensibility and scalability as the major criterion. B. Design Details

1. Knowledge Base:

The knowledge base of the expert system shell stores the extensive knowledge gathered from experts, historical data and books regarding the application in the form of rules. The knowledge can be either factual or heuristic. The knowledge is stored in the form of production rules, which contain if-else rules. The knowledge base is divided into three major sections namely: variable section, rules section and asks section. The variables section is used to declare all the variables used in the knowledge base, the rules section is used to define all the rules used to represent the knowledge and the asks section includes all the questions and options for the user to select and continue with the consultation for getting the required assistance from the expert system. The Fig 2 shows the typical format of the knowledge base required for the expert system.

Fig 2

2. Database Design: The information gathered is either factual, heuristic or

query based. Of the data gathered, the data which can be put in the form of a question and answer are put in the database of the application. The database table of the expert system shell has three fields namely: the id, question and answer. The database can be accessed by entering the keyword related to the information seeked. This leads to displaying of all the questions containing the keyword and selection of any one of the questions would provide for the displaying of the required information.

3. Inference Engine:

It provides the system control. It applies the expert domain knowledge to what is known about the present situation to determine new information about the domain. The inference

Data Acquisition Data Acquisition

Knowledge Base Data Base

Inference E i

DB Tools

Select Knowledge Base

Select Data Base

Main Menu

Graphical User Interface

engine is the mechanism that connects the user input in the form of answers to the questions to the rules of knowledge base and further continues the session to come to conclusions. This process leads to the solution of the problem. The inference engine also enables the expert system's interface to data sources and to the user. The inference engine also supports to identify the rules of the knowledge base used to get decision support from the system and also forms the decision tree. The inference engine is developed using VB.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: a. Input interface b. User interface and c. Working memory

a. Input Interface:

The input interface to the package is through the admin page of the GUI. This allows the expertise to be uploaded as the knowledgebase files in text format and also allows updating the database tables for given equipment by the expert or the knowledge engineer who would act as the administrator for the given package. The input interface has been developed in C#.NET with database support from MS Access.

b

c.

. User Interface:

The user interface to the package is through user page of the GUI. This allows for creation of new users and also allows the existing user to consult the expert system in a user friendly manner for decision support. The user interface has been developed using the C#.NET technology.

Working Memory:

The working memory contains the information that the system has received about a problem at hand. In addition, any information the expert system derives about the problem is also stored in the working memory.

III. Development of an Intelligent Fault Diagnosis and Control Paradigm (IFDCP)

The developed web based expert system shell is now used for the development of an intelligent fault diagnosis and control paradigm. Expert system to be used for fault diagnosis and control calls for a deep knowledge base. This is possible by extensive data collection by the knowledge engineer from the experts in the field, historical data of fault occurrences and from books related to the field. The data thus obtained is put in the form of either if-then rules in the knowledge base or in the form of question and answer in the database table, whichever format the data suits to. The expert in the particular domain should have extreme expertise in his field and preferably should be an "operational engineer".

The knowledge base designed for this application of fault diagnosis and control of power system equipment[4] deals with the symptoms, causes and remedies of various faults

frequently occurring in power system equipment and the specifications and standard ratings of the equipment and also stores data supporting for controlling faults. The data was collected from an electrical factory in Visakhapatnam, India. It is the data about equipment fault, its diagnosis and remedial measures. All the data collected was first put in tabular form for various equipment with equipment name, symptoms, causes and remedial measures as columns. Further they were transformed into decision trees and then as rules in the knowledge base of the expert system package. The equipments considered for this package are: Transformers, DC Motors, AC Motors and Streetlamps.

The total package developed is explained with respect to the transformer module and all other equipment modules have been developed similarly. In case of the transformers in the electrical factory, let us consider a few fault clearance scenarios using the present package.

Based on the visual observations and information received from the sensors fitted to the transformer, the operator can easily detect the temperature rise on the transformer i.e. more than the prescribed value(the prescribed value can be known from the application database), the operator can use the package and select for the equipment transformer and symptom high temperature rise. This in turn leads the package seek information about the type of the transformer which can be known from the application database. The inference engine works on the input in relation with the knowledge base and finally displays the solution for clearing the fault or problem of high temperature rise on the transformer.

In this way any fault related to various power system equipments can be very easily cleared with the assistance of the Intelligent Fault Diagnosis and Control Paradigm (IFDCP). Extensive data has been collected for transformers, street lamps, acmotors and dcmotors and stored in the knowledge base and database of the package. The table, decision tree and knowledge base rules are developed for each and every equipment considered in the package based on the data and information gathered.

The developed package can always be upgraded with new equipments very easily as extensibility is the main feature of our web based expert system package. The web based expert system package (IFDCP) developed can be hosted on web and can be supported on both internet and intranet. Hence the user can use the package from anywhere round the globe. It is very user friendly. It starts with the login page asking for user id and password and also allowing for the registration of a new user. The login page connects the user to the main page displaying the equipment to be selected. This is a dynamic page which updates the images and list of equipments to the user as and when uploaded by the administrator. A click on the image of the required equipment redirects the user to the respective equipment page with options to select for either the knowledge base or the database of the selected equipment. On selecting the knowledge base the user enters into a question and answer session where the user selects for the symptoms based on the physical observations made for the fault. The

session ends up finally providing the user with the remedy for the occurred fault. On selecting for the database the user is provided with a search engine mechanism where the user can get the details of the equipment specifications, ratings and other details by typing the keyword related to the requirement and the package places all the related data from the equipment database. The package gives complete freedom to the user to switch over from one equipment to other and to switch from the knowledge base and the database.

The login with the administrator id and password links to the admin page where uploading of new knowledge bases and updating of existing databases can be easily done.The package once hosted on web for internet services or on local host for intranet services is completely available to the client (user) without any restrictions on the availability of the building technology on the client system. The user can always use the package in any web browsers like IE5 or Mozilla. Etc. as the package is totally user friendly the user is not required to know any technology to work with the package and use it for fault diagnosis and control except for typing the URL to get to the login page.

Snapshot of the developed web based expert system package IFDCP is given as fig. 3.

Fig 3

IV. Conclusions

The design and development of a web based expert system shell and its role in developing an Intelligent Fault Diagnosis and Control Paradigm (IFDCP) package for power system equipment is presented in this paper. A brief description of expert system architecture and issues involved in developing a web based expert system shell and the technology used is discussed. The concept of designing a web based expert system with a user friendly GUI is also discussed.

The application of the shell to develop the package IFDCP for fault diagnosis and control of general power system equipment which provides online help for diagnosing faults of electrical power equipment and clearing them is discussed in detail in the paper. The package deals with data collected from an electrical factory in Visakhapatnam for Transformers, DC Motors, AC Motors and Street Lamps. The package can be easily extended to other equipments also.

The package IFDCP is developed on the basis of expert's past experiences in fault clearance. Thus it renders a cost-effective solution in clearing a fault that may occur again. As

it is a web based application anybody from anywhere can use it for fault diagnosis and control provided he is in the network. The package is very user friendly and is easily extensible.

VI. References

[1] A Moyes, J R Mcdonald, “The Use Of Intelligent Systems Techniques In Condition1 Monitomng Of Electrical Plant” Q3 1997 The Institution Of Electrical Engineers, Printed and Published By The Iee, Savoy Place, London Wcpr Obl, Uk

[2] “Incorporating Expert Systems into web based environment” from proceeding (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 Partial Discharge Monitoring For Power Transformers”, Power Engineering Journal December 2002

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

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