高频脉冲电压下油纸绝缘局部放电特性研究

Partial Discharge Characteristics of Oil-paper Insulation Under High Frequency Pulse Voltage

高频变压器运行过程中油纸绝缘承受严酷的电热应力,绝缘系统容易过早失效。为了研究高频脉冲电压对油纸绝缘局部放电特性的影响,搭建了高频脉冲电压下的局部放电试验平台,开展局部放电试验,研究油纸绝缘在高频脉冲电压下的局部放电特性,并与工频电压下的局部放电特性进行对比。结果表明:高频脉冲电压下局部放电主要发生在电压的上升沿和下降沿,高频脉冲电压下的局部放电幅值远高于工频下的局部放电幅值,在10 kHz附近存在频致拐点,且高频脉冲下油纸试样出现直击现象;究其原因是高频产生较高的电压上升率,改变了缺陷区域的局部场强和高频电热耦合效应,从而导致了局部放电强度的变化。

During the operation of high-frequency transformer,oil-paper insulation bears severe electric and thermal stress,and the insulation system is easy to fail prematurely.In order to study the effect of high frequency pulse voltage on the discharge characteristics of oil-paper insulation,we built a partial discharge(PD)test platform under high frequency pulse voltage to conduct partial discharge tests.The characteristics of partial discharge of oil paper insulation under highfrequency voltage was studied and compared with the characteristics under power frequency voltage.The results show that under high frequency voltage,partial discharge mainly occurs at the rising and falling edge of voltage,the PD amplitude is much higher than that under power frequency,and there is an frequency-induced inflection point near the frequency of 10 kHz.Moreover,oil-paper insulation is punctured under high frequency impulse.The reason is that the rapid voltage rise rate caused by high frequency changes the local field strength and high frequency electrothermal coupling effect at the defect position,resulting in the change of the partial discharge intensity.