Marjanmehr - Electrical Power Research Center Electric Organization of Iran
H-Monsef - Electrical Power Research Center Electric Organization of Iran
Monsef- A - Electrical Power Research Center Electric Organization of Iran
Ranjbar - Electrical Power Research Center Electric Organization of Iran

Power system operation through Energy Management System (EMS) is controlled and guided by decision making of power system skilled operators This parer deals with an expert system which can estimate possible fault sections using information from protective relays and circuit breakers, and assits dispatchers to monitor the faulted sections in a powe system This paper presents a new method for fault section estimation This method makes possible to execute complicated estimation even for large scale power systems It estimat es fault sections based on deep knowledge on protection shemes of power system using cause-effect network In some cases that it can not diagnose the fault successfully, it uses a Rule-Based model This method also can analyse and diagnose the chaining faults using this Model- Rule-Based system As an advantage the developed Expert System does not require any sequences of operations and time-steps Also the primary topology of the power system is considered This Expert System is applied to the 400-230KV IRAN power system network and its respective results are gotten The report of program is very user friendly that the operator could analyse the fault area and their relays and circuit breakers operations