Abstract: According to the characteristics of power system transmission line network model structure, this paper established a power grid fault diagnosis model based on Rough Sets（RS） and Coloured Petri Net（CPN）. Under the premise of keeping the key information, RS can reduce the extracted fault information and obtain the knowledge of the minimal expression. CPN, based on power line junction line analysis function, can build the CPN model of electric power grid fault diagnosis. Examples show the rapidity and simplicity of the diagnosis model, and the combination of two methods not only improves the generality of fault diagnosis but also reduces the complexity of fault diagnosis.

Key words: RS, CPN, fault diagnosis, nodal analysis