Electrical-Thermal Failure of Metal–Oxide Arrester by Successive Impulses

Abstract

This paper focuses on the electrical-thermal multiple-field analysis on degradation and failure of an 110 kV-class surge arrester subjected to successive lightning current impulses by experiment and simulation. Performance deterioration of the arrester under successive 8/20 $\mu$ s lightning strikes was measured. Deterioration steps of $V-I$ characteristics and residual voltage of arrester were detected, revealing a failure threshold of impulse number to evaluate the initial failure of the varistor column. The impulse failures of ZnO varistors were mainly caused by surface flashover and puncture. It is found that the appropriate arrangement of metallic spacers along the column can terminate the consecutive failure of ZnO varistors. To characterize the electrical-thermal effect on impulse degradation, the transient nonlinear finite-element program by an axisymmetric 2-D arrester model was developed to solve the heat generation/dissipation of an arrester during successive impulses. With the combined results of simulation and experiment, it is proved that the discrepancies of heat generation/dissipation along the varistor column cause the arcuate electrical-thermal energy distribution, indicating that degradation of an arrester under successive impulses is governed by the electric-thermal coupling interaction effect.