Influence of oil property on space charge dynamics in oil-paper insulation under DC and AC electric field

Space charge in oil/paper insulation has a close relation to its electrical performance. Space charge characteristics of insulating materials under AC voltage and DC voltage are equally important. There is a huge amount of AC transformers in the power transmission system. However, there is little report about the space charge characteristics of the oil-paper insulation materials under AC voltage. In this paper, firstly, the space charge characteristics of the oil immersed insulating paper with different oil property under the positive/negative DC electric field were investigated using the pulsed electro-acoustic (PEA) method. Secondly, the space charge characteristics of the oil immersed insulating paper with different oil property under power frequency voltage were studied using the improved PEA system. Results show that oil property has an obvious impact on the charge distribution. The more the deterioration of the oil, the larger amount of charges injected into the oil impregnated insulation paper. The charges accumulated within the oil-immersed insulating paper under the power frequency voltage show a significant reduction compared with the results under DC voltage.