An Expert System for Transformer Fault Diagnosis Using Dissolved Gas Analysis 1. INTRODUCTIONThe power transformer is a major apparatus in a power system, and its correct functioning its vital to minimize system outages, many devices have evolved to monitor the serviceability of power transformers. These devices, such as, Buchholz relays or differential relays, respond only to a severe power failure requiring immediate removal of the transformer from service, in which case, outages are in