Fault diagnosis method of substation system using 3/2 connection mode based on the rough sets and Petri net

500 kV and the above transformer substation always select 3/2 connection mode, its structure of the main connection and the protection disposition have its own characteristics. This paper established the initial decision table of fault diagnosis based on analyzing the 3/2 connection system protection trip strategies. Depending on the reduced attribute set based on the rough set theory, we constructed the Petri net model to diagnose the fault. The results of tests show that this method can diagnose the fault part of 3/2 connection mode accurately and it is good at the diagnosis speed and the fault tolerance.