With the increasingly intense competition in the electric power market

it is of much significance to decrease the cost of power production

for which condition based maintenance is an effective way. The expert system introduced in the paper is aimed at predictive maintenance

in which object oriented programming technique

Oracle and Access databases are integrated to render it very flexible and easy to maintain and upgrade. The ultimate character of the system is high versatility. As its rule database is set in a much better way than ordinary rule databases

the expert system can run and elicit results correctly even the database is just modified.