多脉冲雷电冲击下金属氧化物的破坏形式

Failure Modes of Metal Oxide Arrestor Under the Multi-pulse Lightning Surges

氧化锌(ZnO)压敏电阻是金属氧化物避雷器(MOA)的核心器件,对ZnO压敏电阻老化劣化以及破坏形式的研究对于MOA性能的改进具有重要意义。为此,借助同时序多脉冲雷电冲击高电压测试平台,研究了ZnO压敏电阻在动作负载以及不同多脉冲雷电冲击下的性能变化。研究结果表明:(1)多脉冲雷电冲击下,金属氧化物均匀度不同会导致不同的破坏形式,贴片接触结构均匀度较差的金属氧化物的破坏形式主要是贴片的融化剥落,热物理性能均匀度较差的金属氧化物的破坏形式则以ZnO压敏电阻体的热燃烧和粉碎性破裂为主;(2)多次单脉冲雷电冲击会导致ZnO压敏电阻内部损伤积累,破坏形式主要是裂痕和边角损坏,而当多脉冲雷电冲击数量超出一定值时,金属氧化物ZnO压敏电阻的破坏形式则出现分散性;(3)改变雷电冲击中脉冲的数量(10个以内)比改变相邻脉冲雷电冲击的时间间隔(ms数量级)可以对ZnO压敏电阻产生更明显的破坏程度。多脉冲雷电冲击ZnO压敏电阻本身产生的热应力为其劣化损坏的主要原因。

Zinc oxide （ZnO） varistor is the core component of a metal oxide arrester （MOA）. It is important to study aging degradation and failure modes of Zn0 varistors so as to improve the performances of MOAs. On the basis of the simulta- neous multi-pulse lightning high voltage test platform, we presented the changes in performances of ZnO varistors under operating duty tests and different multi-pulse lightning surges. The research results show： （1） Under multi-pulse lightning surges, metal oxides with different homogeneities have different failure modes. For the metal oxide with poor homogene- ity of patch contact structures, the patch is melted and flaked off. For the MOAs with poor homogeneity of thermo physical properties, combustion and crush are the main failure modes. （2） Multiple single-pulse lightning surges have cumulative damaging impacts on ZnO varistors, resulting in crack and damages on the edges. While exceeding a certain number of multi-pulse lightning surges, the failure mode varies for different varistors. （3） Changing the number （10 or less） of lightning pulses in a surge has more obvious impacts on ZnO varistors than changing the time interval （ms） be- tween two adjacent lightning pulses. Analyses suggest that, under multi-pulse lightning surges, thermal stress is the main mechanism for the deterioration of ZnO varistors.