Economic assessment of lightning performance improvement of 69 kV subtransmission line in MEA´s power distribution system

The Back flashover generated from a lightning stroke hit on an overhead ground wire (OHGW) or a pole top 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 circuits installed on the electrical concrete pole by ATP-EMTP. The lightning performance is evaluated in terms of pole top voltage, critical current and back flashover rate. The case studies illustrated the lightning strike to direct pole top and mid span of overhead ground wire. 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 subtransmission lines in MEA.