Capacitor is the key electrical element for the reactive power compensation of cabinet substation.Such problems as swell and rupture etc of capacitor occur due to defect of manufacturing process

improperinstallation and maintenance and severe operation condition and poses a great threat on the safe operationof power grid. At present

the analysis of capacitor fault mainly involves in such aspects as site survey con-dition

operation data and returns to the factory inspection etc. such phenomenon as insulation performancereduction mechanism

partial discharge and overheating of capacitor housing are seldom analyzed by themicroscopic theory. In this paper

the rupture of capacitor is taken as an example and such phenomenon as lossincrease and temperature rise due to excessive moisture penetration into the capacitor is explained from themicroscopic point of view. At the same time

reasons for the bubble source of insulation oil

rupture mecha-nism

partial discharge and excessive internal pressure of capacitor are described in detail. The improve-ment measures from such three aspects as production

installation and operation are proposed so to assurestable operation of capacitor and improve the safety and reliability for the operation of cabinet substation.