Effect of DC voltage with multiple harmonics on space charge behavior in epoxy resin

Epoxy resin has been widely used in dry-type insulation application such as DC dry-type bushings. In practice, DC dry-type bushings work not only under DC voltage, but also under multiple harmonics with 50Hz fundamental frequency. This study focuses on the effects of space charge behavior of epoxy resin on real voltage of DC dry-type bushings. By using Fourier decomposition, the real voltage of DC dry-type bushings can be decomposed into dc voltage with multiple harmonics. In this paper, several typical waveforms, such as 0.1Hz and 50Hz, have been applied on the dc voltage. Obviously, the testing condition should consist with working condition as closely as possible. As the working temperature in the center of the bushings is high, 40°C and 80°C have been selected as testing temperatures. The experimental system is built by PEA method, the space charge testing equipment of which have different strengths of electric field The experimental results demonstrate that multiple harmonics have considerable effects on space charge of epoxy resin in different temperatures and strengths of electric field. Besides, the space charge of epoxy resin will dissipate quickly at a higher temperature.