空间电荷对不同老化状态油纸绝缘击穿特性的影响

Influence of Space Charge on Breakdown Characteristics of Oil-paper Insulation with Different Aging Status

为研究高压直流(HVDC)输电系统中油纸绝缘的老化状态与空间电荷效应对其击穿特性的影响,采用加速热老化处理得到3种不同老化程度的油纸绝缘试样,通过同极性不同幅值的预压方式注入空间电荷,测量其击穿电压;采用电声脉冲法(PEA)在室温下观察试品的空间电荷分布,进一步分析了油纸内部的电场分布情况和陷阱分布特性。实验结果表明:经3 k V同极性预压后试品的击穿电压整体高于未经预压处理的试品;且随着油纸绝缘老化程度的加剧,介质内部浅陷阱密度增大;随着电荷注入量的逐渐增加、电荷效应的增强,击穿电压有所提高。但经4 k V同极性预压后试品的击穿电压整体低于经3 k V同极性预压后试品的击穿电压;因此,在实际运行中,同极性预压幅值超过一定阈值时反而会出现击穿电压降低的现象,应引起特别注意。

In high voltage direct current （HVDC） system, the breakdown characteristics of oil paper insulation are sig- nificantly affected by its aging status and space charge effect. We used the accelerated thermal-aging treatment method to obtain three oil-paper insulation with different aging degrees, and injected the space charge by using pre-voltage with dif- ferent amplitudes and measured their breakdown voltages. Then we used the pulsed electro-acoustic （PEA） method to observe the space charge distribution at room tempera^tre and further analyzed internal electric field and trap distribution within sample. The experimental results show that the overall breakdown voltage of sample after 3 kV pre-voltage is higher than that of sample without pre-voltage treatment. The trap density increases with the aging degree of oil-paper, and the space charge quantity becomes larger, enhancing the space charge effect and breakdown voltage trend. However, the overall breakdown voltage of sample after 4 kV pre-voltage is lower than that of sample after 3 kV pre-voltage. Hence,special attention should be paid that the breakdown voltage of oil-paper insulation will reduce in actual operation when the amplitude of homopolarity pre-voltage exceeds a certain value.