Computation of Arrester Thermal Stability

Full-scale thermal stability type tests on substation class metal oxide arresters are not practical. As a result, standards such as IEC 60099-4 specify the use of a reduced-scale model and define test methods which are intended to assure that the reduced-scale model is conservative relative to the full-scale arrester. The authors succeeded in computing the thermal stability of full-scale arresters based on the operating duty arrester type test specified in IEC60099-4 and ANSI in a few hours using transient nonlinear finite element software customized for the purpose. Based on these computations, the cooling mechanism of a polymer arrester and the effect of arrester structure on thermal stability could be evaluated. The authors are continuing this approach with the expectation of achieving more accurate prediction of full-scale arrester stability computationally than can be achieved using reduced-scale models. The present paper contributes to the understanding of appropriate reduced-scale models, their relationship to the thermal stability of full-scale arresters, and how to define the thermal stability of a full-scale arrester.