Design of Parallel Protection Air Gap of 35 kV Transmission Line Arresters

The 35 kV power transmission line is not equipped with lightning conductor, resulting in the frequency of lightning strike line and the current generated by lightning strike lines are much larger than those with 110 kV voltage level and above. As the current carrying capacity of the arrester of 35 kV line is insufficient, the arrester is frequently damaged due to lightning strikes. To improve the performance of arrester, this paper proposes a parallel protection air gap of 35 kV line arrester. The structure and distance parameters of protection air gap were obtained by the volt-ampere characteristic curve of zinc oxide (ZnO) resistance and air gap discharge test. When the amplitude of lightning current is lower than the protective action threshold, the voltage of arrester is lower than the parallel gap discharge voltage, and lightning current flows through ZnO resistance. When the lightning current amplitude is higher than the protection action threshold, the voltage of the arrester breaks down the parallel air gap, preventing the arrester from being damaged by lightning. The impulse discharge test and field application of 35 kV line arrester show that the parallel air gap can reduce the lightning damage probability of 35 kV line arrester.