Based on parameterization functions

this paper introduces six typical time-frequency energy distributions known as the Cohen′s class.From a theoretical point of view and application

the interference cross-terms attenuation and time-frequency resolution of those distributions have been discussed respectively.According to the characteristic of non-stationary partial discharge（PD） signals

these distributions have been applied to simulation PD signals and the real ones.The results show that the smoothing-pseudo Choi-Williams distribution（SPCWD） provides a high sensitivity to variation in short duration of the non-stationary PD signal

which is available to extract the time-varying information.This distribution provides a powerful tool to evaluate parameters for single PD pulse shape and analyze time-frequency variation of PD sequence

which can be used to PD pattern recognition and in-depth study of PD mechanism in the electrical insulation system.