In order to distinguish the high-frequency partial discharge signal coupled from power transformer bushing tap

which generated in a tank or in a bushing

an experimental device containing a bushing with a capacitor shield tearing defect and a detachable needle-plate discharge defect model was constructed. The high-frequency partial discharge signals were generated by applying calibration pulse and high voltage on defects at different positions

and were coupled from power transformer bushing tap. Three methods of time-frequency analysis

based on short-time Fourier transform

synchro squeezed wavelet transform

and synchro extracting transform

were proposed to analyze these signals. The time-frequency spectrum distinguishable effects of three methods were compared

and a time-frequency spectrum post-processing method was proposed. The research shows that the sources of high-frequency partial discharge signals can be distinguished by their time-frequency spectra

which are influenced by transmission paths.Meanwhile

compared to the synchro squeezed wavelet transform

and the short-time Fourier transform. The time-frequency spectra generated by the synchro extracting transform are better for signal sources distinction.