The polypropylene film

the medium for the all-film capacitor

is used widely in the manufacture of shunt capacitor of power systems due to its series of such advantages as high breakdown field strength

low dielectric loss

good specific characteristics and reliable safe operation. In this paper

the shunt capacitor is taken as the research object. The breakdown characteristics of insulation medium of the shunt capacitor under AC and DC voltages are

in case of immersion and non-immersion condition

studied respectively.The statistics of breakdown data and the positions of breakdown point of the elements are made and the test phenomena are analyzed. The test results show that in case of oil immersion condition

the average breakdown field strength of the insulating medium of the full film capacitor at AC voltage is 279.05 V/μm and the breakdown is likely to occur in the middle area of the element. The average breakdown field strength at DC voltage is 435 V/μm and the breakdown easily occurs at the edge of electrode of the element.