Space charge characteristics of epoxy-creped paper composites

In order to study the interfacial effect on space charge distribution in HVDC bushings which impregnated with epoxy resin, samples just like epoxy-impregnated paper-epoxy were prepared by vacuum casting process. Space charge characteristics have been studied by the method of pulsed electroacoustic (PEA) technique at different electric fields and temperatures, including charge polarity, charge amount, the threshold for space charge accumulation. It was found that the polarity of the interfacial charge was related to electric field and temperature. When at 20kV/mm, 313K, there was heterocharge at the interface between epoxy and impregnated paper. But when temperature went up to 353K, homocharge accumulated at both interfaces. However, when at 10kV/mm, there was heterocharge whether the temperature was 313K or 353K. At the same time, threshold for charge accumulation reduced when temperature went up. Above phenomenons were thought to be the result of dielectric polarization and charge injection.