Operational experience and maintenance of an on-line expert system for customer restoration and fault testing

CRAFT (customer restoration and fault testing) is a rule-based expert system capable of locating the faulted section of a power transmission line based on the status of circuit breakers an automatic switches. CRAFT has been operating online in the Puget Sound Power and Light control center since July 1988. The online operational experience is reported. Many of the developed expert systems will be maintained or modified by utility engineers. This study proposes a methodology for maintaining rule-based expert systems. The following capabilities are incorporated: detecting the relations of conflict, redundancy, etc., to maintain consistency of the rule base, tracing the reasoning process to understand the problem solving approach, and reducing the size of test cases after changes are made to the rules. The proposed method has been implemented for CRAFT