Temperature and DC Electrical Field Strength Effect on Volumetric Conductivity of Epoxy Impregnated Paper

The extra-high voltage converter valve side bushings is key equipment in UHV DC transmission project, which run under high voltage and high current. The epoxy impregnated paper composite insulation system as its main insulation also has salient change in its electrical properties due to long-term operation under complicated working conditions, which has great impact on the insulation status of the valve side bushing. Therefore, this paper focuses on the volumetric conductivity of two epoxy impregnated paper samples that one is sprayed insulation paint and the other is not under different temperature and DC electric field strength combination test condition based on polarization and depolarization current method(PDC). The results show that increasing temperature and DC electric field strength both lead to increase of epoxy impregnated paper volumetric conductivity. The effect of temperature on volumetric conductivity is weakened by DC electric field strength. In addition, spraying insulation paint leads to the volumetric conductivity of the epoxy impregnated paper decrease significantly. The volumetric conductivity decrease varies under different combinations of DC electric field strength and temperature.