Space Charge Characteristics of Different Oil-Immersed Papers under Polarity Reversal Voltage

In order to ensure the supply of high quality oil for high voltage transformers and promote the reliability of transformer oil, the space charge distribution in five different transformer oil-immersed papers before and after polarity reversal were compared. Firstly, the space charge measuring platform was established with pulsed electro-acoustic (PEA) method. Then, five kinds of oil-immersed paper were made as sample, of which the oil are KI50X, KI45X, S4, HI50X and S4-KI50X mixed (1:1), respectively. Finally, the space charge measurement was performed to investigate the influence of oil on the space charge characteristics in oil-immersed paper under polarity reversal. Results indicate that all kinds of oil-immersed papers share the similar polarization process, with space charge accumulation of the same polarity. However, the electric field of different transformer oil-immersed papers appear large difference, where sample of KI50X gets the least accumulation of opposite polarity charge after polarity reversal, while samples of HI50X and KI45X get the most. In the polarity reversal, different degrees of electric field distortion inside the oil-immersed papers are computed, by order from max to min are KI45X > HI50X > S4 > S4-KI50X mixed > KI50X.