An improved thermal damage evaluation method for lightning-induced failure analysis of overhead ground wire

Abstract

In the research of lightning-induced damage mechanisms for overhead ground wire (OGW), thermal ablation damage evaluation has always been a basic work. In this paper, a numerical evaluation model of thermal damage for OGW, considering the latent heat of phase transition and mass loss caused by vaporization, is proposed. The influence of the phase transition effect on the thermal damage evaluation results was analyzed, and the damage characteristics under different lightning heat sources were also discussed. Finally, this model was compared with the published experimental data and the OGW damage sample caused by natural lightning strikes, respectively. The results showed that in the case of ignoring the latent heat of phase transition and mass loss, the maximum assessment deviations exceeded 190% and 45%, respectively. Under the continuing current, the thermal ablation damage of OGW was determined by the heat transfer of lightning arc. While under the return-stroke current, the contribution of Joule heat to thermal ablation increases as the current increases. Based on the existing Joule heat & arc heat transfer model, the damage evaluation results considering the phase transition effect were consistent with the reported experimental results. However, it cannot match the OGW damage sample results. This issue deserves further discussion.