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Development Of A Non-Fragmenting Distribution Surge Arrester

Failure of a distribution surge arrester can result in fracturing of the porcelain housing. Although the probability of an arrester failure is extremely low, the cumulative number of failures could be substantial because of the large number of arresters installed. This paper reports the results of an EPRI funded research project directed towards eliminating, or substantially reducing, the hazard associated with the fragmentation failure of distribution surge arresters. It is commonly assumed that pressure buildup in a failing surge arrester will cause the porcelain to burst unless the pressure is rapidly relieved. Even after pressure relief, however, the porcelain can shatter from the thermal shock produced by the internal arc. There is little published information on the sequence of events during failure and the relative importance of pressure and thermal stress. A prerequisite for the design of a non-fragmenting arrester is a thorough knowledge of the failure mechanism. Extensive testing was performed to determine the contribution of both pressure and heat to porcelain breakage. This research demonstrated the importance of thermal shock and led to the design of an ablative thermal shield for the porcelain housing. The final result was the design and production of non-fragmenting distribution arresters rated 9 kV through 27 kY.