Validating surge test standards by field experience: high-energy tests and varistor performance

Proposed IEEE and IEC high-energy surges tests and surge-test modeling are reviewed. The results of modeling the application of a surge test to a family of commonly used varistor sizes (14, 20 and 32 mm diameter) are discussed. For each varistor size, the computations were performed for three levels of manufacturing tolerances on the varistor: nominal value, -10%, and +10%. The results were obtained by quantifying the current through the varistor and the corresponding energy deposited in the variator. The computed results are compared to the published device ratings to predict the likelihood of failure. This likelihood is then compared to the available information from field experience on failure rates.<>