In view of the problem that IEC three ratio method has the disadvantage of absolute boundary and lack of codes

a novel transformer fault diagnosis method based on generalized regression neural network（GRNN）and Fuzzy C-means（FCM）clustering algorithm is proposed and a GRNN-FCM combined transformer fault diagnosis model is constructed. Five volume fractions of the gases in oil and its three-ratio codes are chosen to be the inputs of the combined model. This model uses GRNN model to judge the preliminary fault type（normal

overheat

discharge

discharge & overheat）

then Fuzzy C-means clustering algorithm is adopted to achieve the transformer fault diagnosis. After comparing the combined model to other two diagnosis methods

the simulation results indicate that this combined model has accordant outputs with the measured values and provides higher accuracy

so the feasibility and effectiveness of the model presented are verified.