500kV断路器均压电容器10kV介损异常现象的研究与探讨

Study and Discussion on Abnormal Phenomenon of 10kV Dielectric Loss of Grading Capacitor for 500 kV Circuit Breaker

双断口断路器通常在两个断口分别并联均压电容器,以减小杂散电容引起的断口分压不均,保证两个断口承担相同的电压,并限制断口恢复电压陡度,提高断路器的工作可靠性。在均压电容器预防性试验中,发现部分全膜绝缘和膜纸复合绝缘均压电容器出现10kV介损超标或增长较快的现象。对5台缺陷电容器进行了高电压介损、耐压和局部放电等试验,以及绝缘油理化分析和解体等工作,判断绝缘油理化性能劣化和心子击穿是均压电容器10 kV介损超标或增长较快的直接原因,认为高电压介损试验不能作为均压电容器是否具备继续运行条件的唯一标准。基于上述工作,对均压电容器的预防性试验工作提出了建议。

Grading capacitor is normally parallel with two interrupters of circuit breaker(CB)respectively in order to reduce the uneven voltage division of interrupter due to stray capacitance,assure the two interrupters to bear the same voltage,limit the recovery voltage gradient and improve the operation reliability of circuit breaker. It is found in the preventative test of the grading capacitor that partial full film insulation and film paper composite insulation grading capacitors have the phenomena of 10 kV dielectric loss exceeding standard or fast increase. Such tests as high voltage dielectric loss,withstand voltage and partial discharge on 5 pieces of defect capacitors and the works such as physical and chemical analysis of insulation oil and disassembly are performed. It is judged that the direct cause for exceeding standard or fast increase of 10 kV dielectric loss of grading capacitor is due to physical and chemical performance deterioration of insulation oil and core breakdown,thinking that high voltage dielectric loss test cannot be regarded as the only standard whether the grading capacitor possesses continuous operation condition. Based on above work,the suggestion for the preventative test work of the grading capacitor is proposed.