Modelling of a transmission tower for lightning-surge analysis

Modelling of transmission towers is an essential part of the travelling-wave analysis of lightning surges in overhead power-transmission lines. In the paper an equivalent distributed constant line model of a transmission tower is developed. The model consists of three parts: main legs, bracings and crossarms. The surge impedance of each part is expressed by the functions of their dimensions and geometry. This tower model is applied to a 500kV transmission tower whose surge performance characteristics are measured. It is found that the tower voltage wave shapes, calculated from this model, closely agree with the measured ones. This proves that the authors' proposed tower model simulates well the surge performances of actual transmission towers.