Detection and treatment of internal solid insulation defects by ultra-high frequency（UHF）partial dis-charge method is an important measure for operation and maintenance of gas insulated switchgear（GIS）. At present

the accuracy of the method of comparing abnormal UHF signals with current standards

specification and typical sim-ulation defect atlas to diagnose defect types and severity still needs to be improved due to complex site conditions andvarious structures of equipment. Therefore

in this paper

in view of discharge defects of solid insulation surface andof internal sphere gap of GIS

which is found at site detection

PRPS（phase resolved pulse sequence）statistical spec-trum characteristic of UHF partial discharge signal excited by such type of defect is studied. The spectrum and time-frequency characteristics of single UHF original pulse is analyzed by Fourier transform and continuous wavelet trans-form. The summary of the pulse duration

discharge numbers

phase width

polarity effect

frequency domain distribu-tion and time-frequency characteristics of various solid insulation discharge defect signals can help optimize theUHF detection frequency band

improve the detection sensitivity of insulation defects and can be beneficial for the in-spectors to identify more accurately the discharge type and comprehensively diagnose the defects as well as improvethe defect detection and diagnosis level at site.