Contribution à l'étude de performances électriques des parafoudres synthétiques sous tension alternative

Abstract

The purpose of this work is the study of the effect of pollution on the behavior of synthetic surge arrester. We are primarily interested on the influence of the dry band formation and with the restarting of the discharge on the external leakage currents which flow in the contaminated surface and the internal current which flows across the varistors column. The suitable evaluation of the risk of starting would allow not to practice this operation, expensive and often awkward for the exploitation, that when it is necessary. The knowledge of the leakage current crossing insulation and its time evolution would allow achieving this goal. In order to better understand the effect of pollution on the electrical field and stress distribution along the synthetic surge arrester, a series of layer pollution case distribution and for several values of conductivity was made in a first stage. COMSOL Multiphysics Software was used for this purpose. After that, a formed equivalent circuit of capacity and resistance was derived and its parameters are identified by the finite element method. The equivalent circuit was implemented in the ATP/EMTP to simulate the internal and external leakage currents of the surge arrester, and satisfying results were obtained. The discharge across the dry band was simulated by adopting an insulators flashover dynamic model, which uses the Hampton's propagation criterion, and the Rahal's speed expression. This model was established in the equivalent circuit of the surge arrester to simulate the discharge.