Lightning protection of unshielded overhead medium voltage power lines in South Africa

Abstract

South Africa has an extensive overhead electricity distribution network at medium voltage (MV). It also has a significant amount of lightning in most areas. The purpose of this paper is to report on South African experiences with respect to lightning protection of its overhead MV power network, and how designing a line for acceptable lightning performance impacts other aspects such as bird safety, pollution performance and terminal equipment reliability. Strategies covered include different insulation levels, bonding and earthing arrangements and pole-top configurations. Experiences from the laboratory and the field are included. It is concluded that the presently used configuration of a partially bonded structure with lightning insulation level of 300 kV performs more than adequately, but that initial experience with alternative configurations indicates that the network performance could be optimised.