直流预压对油纸复合绝缘局部放电特性的影响

Effect of Preloaded DC Voltage on Characteristics of Partial Discharge in Oil-paper Insulation

为了研究直流预压对油纸绝缘交流局部放电特性的影响,对预压不同时间、不同幅值直流电压以及去极化后重复加压情况下的油纸绝缘交流局部放电特性,不同预压时间和去极化后的油纸绝缘材料的空间电荷特性进了研究。研究结果表明,随着预压直流电压幅值的增大和预压时间的延长,放电起始电压和熄灭电压减小;随着重复加压次数的增多,放电起始电压先上升后下降,但均低于未预压下局部放电起始电压。分析表明预压直流30min后油纸绝缘空间电荷分布达到平衡状态,预压时间越长,去极化后油纸绝缘材料残余空间电荷数量越多;同时长时高幅值预压会使得与高压电极接触的绝缘纸板表面电荷分布均匀,从而改善油纸绝缘内部的电场分布,进而影响油纸绝缘的局部放电特性。

To study the effect of preloaded DC voltage on characteristics of AC partial discharge in oil-paper insulation, we investigated the characteristics of partial discharge in oil-paper insulation under different DC voltage, preloaded voltage time, and AC voltage repetition times.Meanwhile,we investigated the characteristic of space charge distribution in oil-paper insulation under different preloaded voltage time and depolarization to explore the effect on the partial discharge inception voltage（PDIV） and extinction voltage（PDEV）. The results show that PDIV and PDEV of oil-paper decrease with longer preloaded voltage time and higher preloaded DC. The PDIV and PDEV are lower than those in the absence of preloaded DC voltage. Further analyses reveal that the space charge at the interface of oil-paper insulation is a main reason for discharge voltage decreasing. The space charge distribution of oil-paper insulation under DC voltage reaches a balance condition after 30 min under different preloaded voltage time. The amount of residual charge is more with longer preloaded time. The space charge has an aging effect on the surface of oil-paper which is closed to the HV electrode under longer and higher preloaded DC voltage, and results in distorting the distribution of electric field in oil-paper insulation, further has an effect on the partial discharge characteristics of oil-paper insulation.