Abstract
We measured an electric field in transformer oil/pressboard composite insulation system under dc voltage application using Kerr electro-optic measurement system. When a pressboard was inserted between two parallel-plane electrodes, the electric field between the pressboard and the cathode decreased monotonously with time. On the other hand, the electric field between the pressboard and the anode increased with time, reached a maximum value and then fell down.
In this paper, we measured an electric field in transformer oil/pressboard composite insulation system at different time of dc polarity reversal. Firstly, we studied a peak Value of electric field at anode side. Max. 2.4 times higher electric field appeared under dc polarity reversal condition. Secondly, we discussed this phenomenon by charge accumulation and potential distribution model considering the difference in charge accumulation rate on the pressboard surface between positive and negative charges. Finally, we estimated the velocity of the charge accumulation rate using numerical simulation model.
