A comparison between two tower models for lightning surge analysis of 77 kV system

This paper investigates characteristics of a multistory tower model and a distributed line model, in comparison with field test results of back flashovers on a 77 kV transmission line for summer lightning. The multistory tower model composed of distributed parameter lines and parallel R//L circuits, is being used as a detailed model in Japan, and the distributed line model, composed only of distributed parameter lines, has been widely used as a simple model. EMTP simulation results by the multistory tower model show that most flashovers, occur on an upper phase, while the field test results show a uniform distribution of the flashovers on every phase. Simulation results by the distributed line model agree well with the field test results. However, a surge impedance of this model is constant, independently from a configuration of a given tower, and a basis of parameters is not clear. Thus, it is said to be necessary to develop a tower model for a back-flashover analysis on a low-voltage transmission line considering the tower configuration