Effects of oil thermal aged states on the space charge behavior in oil-paper insulation

In order to understand effects of oil thermal aged state on space charge behaviors in oil-paper insulation further, transformer oil with different aged states is prepared by accelerated thermal aging. What´s more analysis on physical and chemical properties of oil is made. The samples are made of new kraft paper which is dried in vacuum and oil with different thermal aged states. The pulsed electro-acoustic (PEA) method is used for space charge measurement under conditions of both voltage-on and voltage-off at room temperature(15°C). The impact of oil aged state on space charge injection, accumulation and decay characters was discussed. The experimental results show homo-charge inject into samples when the voltage is on. The more the oil aged state is, the larger the total space charges quantity and the area of negative charges. For voltage-off condition, aged oil-paper samples are beneficial to space charge decay.