一起由接地网引起的电容式电压互感器故障分析

Analysis on Fault of Capacitive Voltage Transformer Caused by Grounding Network

针对保护装置发信号后出现电容式电压互感器二次侧无电压输出的故障情况,对故障设备进行试验及解体,发现电容器尾端保护间隙铜球及电磁单元一次引线弯折处有明显放电痕迹;氧化锌避雷器被击穿;一次对二次的绝缘降低。用绝缘材料对绝缘损伤进行包扎并固牢,更换氧化锌避雷器。电磁单元在感应耐压过程中无击穿闪络现象,耐压前后的绝缘电阻无任何异常,试验合格。故障分析表明:电容式电压互感器接地网的损坏在电磁单元产生过电压,导致故障发生。针对引起故障的原因提出了相应的防范措施。

Aiming at problem of that there is no voltage output at the secondary side of capacitive voltage transformer after the protector has sent out signals, this paper discusses test and disassembly check for the faulted equipment and discovers ob- vious discharging trace on the copper ball in protective gap at the end of capacitor and at the buckling place of the primary lead of electromagnetic unit. Meanwhile, the zinc oxide arrester is broken down and insulation of the primary lead towards the secondary lead is decreasing. It proposes to wrap up and reinforce the insulation deterioration by using insulation materials and change the zinc oxide arrester. Practice shows there is no breakdown and flashover in process of induced over voltage withstand test for the electromagnetic unit. In addition, the insulation resistance is normal before and after the over voltage withstand test which means the test is qualified. Fault analysis indicates the reason for fault is over voltage of the electromag- netic unit due to damage of the CVT grounding network. Aiming at the above reason it proposes relevant precautionary measures.