Comparison of ANSI, IEC, and CSA standards' durability requirements on station-type metal oxide surge arresters for EHV power systems

An analysis of stresses applied to two types of station class surge arresters of the same voltage rating when tested for durability as prescribed by American (ANSI), International (IEC), and Canadian (CSA) standards for 315 kV and 735 kV power systems is presented. The analysis, which is made with an experimentally validated arrester model, reveals that the IEC duty cycle test is the most severe of all. It can bring the varistors of an actual station-type arrester to a peak temperature of 129 degrees C, which leaves a margin of only 46 degrees C to its thermal stability limit at maximum continuous operating voltage. Another actual arrester using lesser V-I-T varistor characteristics but larger varistor volume and better heat transfer from inside to outside the arrester produces 103 degrees C, which corresponds to a slightly better temperature margin of 49 degrees C. It is observed that, even when using the lower-performance V-I-T characteristics of the latter arrester, a thin-wall arrester housing design can improve heat transfer to a point where the margin improves to 101 degrees C on a hypothetical arrester.<
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