This paper develops a fault diagnosis system for the regional power network by making use of the dual-source data from the SCADA system and the fault information system

which the system can diagnose the fault with the reasoning method of layered diagnosis and cause-and-effect logic. Matching the faulty change information of the protections and the breakers from the dual data source to the main station

the system reasons among the protections

the breakers and the fault equipment to detect the faulty one

with the diagnostic report shown. Moreover

the system has already been applied to the Lanzhou power network and its practicability and veracity has been proved with the result of local operation.