Lightning Protection of 10 kV and 35 kV Overhead Lines Against Direct Lightning Strikes

In this paper is analyzed application of the shield wires, line arresters (LA) and underbuilt wire in lightning protection of 10 kV and 35 kV overhead distribution lines (ODL) against direct lightning strikes. The back-flashover rate of ODLs is calculated by using semi-statistical calculation procedure suggested by CIGRE. Analyzed lightning protection systems have the highest efficiency for low values of the tower grounding resistance, while the increase of it significantly reduces efficiency of protection systems. The best lightning performance can be achieved by using LAs parallel to all line insulators at the critical ODL spans. The probability of span flashovers in that case is very small. Energy stress of the LAs is calculated for cases when ODL is without and with shield wire, with shield wire and underbuilt wire, with shield wire and two LAs in parallel per every line insulator.