A metal oxide arrester (MOA) accident occurred in a tropical coastal area is studied in this paper. The control test and disassembly analysis for the MOAs in the accident group and the control group were conducted. It was considered that the varistors of the MOA were deteriorating. Although the performance of the zinc oxide (ZnO) varistor is qualified, its side insulation glaze has defects. The leakage current under U_1mA and 0.75 U_1mA have exceeded the standard requirements due to the decrease of insulation performance. An electrothermal model of the MOA was constructed. The root-mean-square (RMS) value of the voltage across the varistor column and the RMS of leakage current flowing through the varistor were obtained through simulation. The heating power was calculated as the heat source input of the thermal circuit model to calculate the temperature of the varistor. It was verified that the electrolyte deposited on the surface of the porcelain house due to salt spray formed a dry area after being affected by moisture, because of the uneven potential distribution, the radial current flowing to the varistors through the coupling capacitor on the surface of the porcelain house increased sharply, and it caused the varistor to generate a large amount of heat in extreme condition. The side insulation glaze of the varistor was damaged by frequent heating effect. Eventually, the internal flashover occurred in the MOA, and the internal pressure rose sharply then broke through the explosion-proof film, causing an accident.

本文研究了热带沿海地区发生的金属氧化物避雷器（MOA）事故。对事故组和对照组的MOA进行了对照测试和拆卸分析。认为MOA的压敏电阻正在恶化。尽管氧化锌（ZnO）压敏电阻的性能合格，但其侧面绝缘釉存在缺陷。在U _1mA和0.75 U _1mA下的泄漏电流由于绝缘性能下降，已超过标准要求。建立了MOA的电热模型。通过仿真获得了压敏电阻柱两端的电压的均方根（RMS）值和流经压敏电阻的泄漏电流的RMS。计算热功率作为热回路模型的热源输入，以计算压敏电阻的温度。验证了由于盐雾而沉积在瓷器房表面的电解质在受潮后形成干燥区域，由于电位分布不均匀，径向电流通过耦合电容器流到压敏电阻的表面。瓷屋急剧增加，导致压敏电阻在极端条件下产生大量热量。频繁加热会损坏压敏电阻的侧面绝缘釉。最终，内部闪络发生在MOA中，内部压力急剧上升，然后突破了防爆膜，引发了事故。