Thermal Behavior Analyses of a Polymeric Surge Arrester by Computer Simulations

Summary

Zinc oxide (ZnO) based surge arresters are applied in electric power systems and provide protection for transmission lines and power equipment. During the occurrence of lightning or switching surges, a voltage level above the equipment insulation level can be reached. A defective arrester may not be able to provide the proper protection level in substations, exposing the equipment and personnel to damage. Electrically, an arrester, properly working, is able to limit this voltage level avoiding damages to the protected equipment. And, thermally, a surge arrester, in good condition, should be able to deal with the surge current by absorbing its energy and dissipating it to the environment. Otherwise, if the arrester presents some problem or if it is not correctly dimensioned, it can be lead to a thermal runway, when temperature and current are increased continuously, leading to the equipment break up. Power companies have applied thermal monitoring to most equipment in substations. In this paper, the thermal behaviour of a polymeric 120 kV surge arrester will be analyzed by computer simulations. Simulations present several advantages, such as the possibility of a previous analysis before manufacturing and lower cost when compared with laboratory tests. The aim of the work is to analyse the absorption capacity and the arrester heat transfer. Temperature levels at several points of the arrester will also be analysed, i.e., varistors column, polymeric housing and the terminals interfaces. The IEC duty cycle test will be computationally simulated using COMSOL Multiphysics®, a software based on the finite element method. Additionally, overvoltages will be also simulated using power frequency and considering aging conditions. Based on the results of the simulations, a proposal is made for the analysis of surge arresters in field.

Additional informations

Authors

Babizki Alexei, Sonoda Toyoaki, Ohtsuka Shinya, Inami Kiyoshi