Effect of external ground on lightning performance of 69 kV and 24 kV circuits in MEA´s distribution system

Back flashover generated from a lightning stroke hit on an overhead ground wire or a pole is one of the major causes of sustained interruption in Metropolitan Electricity Authority (MEA)´s distribution system. One effective way to reduce the effects of lightning overvoltage from back flashover is an attachment of external ground wire connected between the overhead ground wires and a ground rod. This paper analyzes the effects of lightning performance of 69 kV and 24 kV circuits installed on the same pole by ATP-EMTP. The lightning performance is evaluated in terms of top pole voltage, critical current and back flashover rate. The study results show that external ground wires can contribute toward improving these three performance indices and therefore offers a promising solution to improve reliability of the double-circuit subtransmission and distribution lines in MEA.