一起变压器雷击故障的分析

为了研究某高压厂用变压器在雷击后造成机组停运的原因,分析了故障录波,开展了高厂变的油色谱、绝缘电阻、直流电阻、直流耐压泄漏电流、介质损耗、低电压短路阻抗、交流耐压等试验,得出了变压器在承受较大短路电流后绝缘正常,故障的发展首先是两相短路、后发展为三相短路的判断。在现场测绘防雷接地布置的基础上,结合土壤、雷声和弧光情况,计算并推断了雷电反击过电压使得绝缘闪络,后在工频电压作用下持续电弧放电,造成高厂变低压侧母排两相及三相短路的过程,分析得出故障原因为变压器区域墙顶的避雷器接地引下线布置安装不能满足标准规定要求。最后提出了相应的防范措施,为类似雷电反击事故的分析提供具有重要参考价值的信息。

Analysis on a Transformer Lightning Accident

In order to investigate the causes for generator outage after a high-voltage auxiliary power transformer of a power plant experienced a lightning, the fault wave record was analyzed and tests were conducted on the oil chromatogram, insulation resistance, DC resistance, DC leakage, dielectric loss, low voltage short circuit impedance and AC voltage endurance. It was judged from the test results that the transformer worked normally after experiencing a large short-circuit current and the fault was caused by two-phase short-circuit and subsequent three-phase short-circuit. Based on the investigation of lightning protection grounding layout, with consideration of the condition of soil and thunder arc, the fault process is calculated and inferred that the lightning overvoltage firstly caused insulation flashover, and then continuous arc-discharge occurred under power frequency voltage, which in turn caused the two-phase and three phase short-circuit of the transformer’s low voltage side bus. Analysis indicates that the cause for the fault is that the layout of lightning arrester’s grounding wiring on the transformer’s wall area failed to meet the standard provisions. In the end, several countermeasures are put forward, which can provide an important reference for similar lightning fault analysis.