Analysis of MOA Damage Mechanism Under Multiple Strokes

Accident records from the actual operation of metal oxide arresters (MOAs) indicate that even MOA products that have passed standard tests still suffer from frequent damage. This phenomenon may be related to the fact that the current standards for MOA testing do not cover multiple stroke conditions. To investigate the damage mechanism of MOA under the effect of multiple strokes, this study conducts continuous current impulse tests on MOA and simultaneously performs finite element simulation analysis. A comparative analysis of the test and simulation results shows the following: The continuous impulse discharge process of multiple strokes causes instantaneous heat accumulation in the varistors, leading to a sudden temperature rise and inducing significant non-uniform thermal stress in the varistors; Under the condition of consistent total impulse energy, multiple strokes are more likely to cause damage to MOA varistors. Moreover, the higher the amplitude of the lightning current in multiple strokes, and the shorter the impulse interval, the higher the risk and degree of thermal damage to the MOA varistors; By analyzing the rate of change in the maximum thermal stress of the varistors, the significant effective range of the superposition effect of multiple strokes under different impulse intervals can be obtained.