Winding fault diagnosis of power transformer is the key technology to ensure the safe operation of powertransformer. Combining the finite element method and the high-frequency equivalent circuit

a transformer windingfault diagnosis method is proposed in this paper. It can effectively improve the reliability of fault diagnosis based onthe ideas of building a relationship between structural faults

electrical parameters

and test results. Based on thefinite element model built in Ansoft Maxwell

the main electrical parameters of the transformer

such as thegrounding capacitances and the inter-disk capacitances

are

calculated. The effect of transformer winding fault onthe changes of the electrical parameters is explored in detail. A high-frequency equivalent circuit is built using thecalculated parameters. In this paper

the axial displacement fault is taking as an example to obtain the curves offrequency response analysis（FRA）under different fault degrees. The results of simulation shows that the change ofthe FRA curves at the selected frequency band（200

2

50 k Hz）are arranged along a curve which can be describedby a cubic function and a parabolic function

respectively. It should be regarded as a diagnostic band to predict thetendency of FRA curves caused by axial displacement. Therefore

the proposed diagnosis method can guide thetransformer winding fault diagnosis

and directly bridge the types and degrees of the faults with the test results.