In simulating lightning flashover process

tower model has a great influence on the electric potential distribution of a tower body. In this study

to more effectively calculate the lightning protection performance of an ultra-high voltage（UHV） transmission line

an improved single impedance tower model is constructed

which is composed of many single surge impedances with different lengths. The improved single impedance model is compared with the traditional lumped inductance model

the single wave impedance model

and the multi-wave impedance model to obtain their different characteristics and applications. The recommended values of the improved single impedance model for the multi-circuit transmission line on one tower are derived at the voltage grades of 110

220

500 k V. It is shown that the electric potential distribution on a tower body calculated with the improved single impedance model is more close to that calculated with the multi-wave impedance model

and the improved single impedance model can largely reduce the amount of computation with satisfactory accuracy. Therefore

the improved single impedance model can replace the multi-wave impedance model for lightning flashover analysis.