Disc-type spacers in gas insulated switchgear（GIS） are usually made of epoxy resin

thus the surface flashover related to the existence of surface charge often occurs under both AC and pulse voltages. In order to study the effects of AC and pulse voltage combination on surface charge accumulation and decay

epoxy resin samples were corona charged and the surface charge distributions were measured by an electrostatic voltmeter. Moreover

the effects of different pulse amplitudes

pulse polarities and pulse numbers on the surface potential were investigated. The results reveal that when negative pulses are applied after AC voltage

the absolute value of initial surface potential decreases first and then increases with the increase of pulse amplitude. When positive pulses are applied after AC voltage

the initial surface potential changes from negative to positive as the pulse amplitude increases. In addition

with the increase of pulse number

the initial surface potential and charge decay rate change in different ways.