Improving lightning performance in PEA distribution system in case of low grounding resistance

Lightning performance improving by installing the overhead ground wire (OGW) can be effective in case grounding resistance or tower footing resistance in the transmission system is low. However, it is not much effective in the distribution system with low CFO of insulator. Generally, the CFO in distribution system of Provincial Electricity Authority (PEA) is triple lower than the one in PEA 115 kV transmission system; therefore, the fault due to lightning surge frequently occurs in the distribution system with low tower footing resistance especially the severe lightning activity which generally occurs in the central area of Thailand. In this paper the study of the effectiveness of lightning protection methods, such as lowering the tower footing resistance, installation of additional OGWs, top phase arrester protection, improving distribution line insulation level is taken by using lightning performance design workstation (LPDW) program of EPRI, after that the suitable methods of lightning performance improving in PEA distribution system with low grounding resistance and frequent outage due to lightning surge have been proposed. The trial use in the system with fault problem has been launched as a case study at feeder 4 Bangsai substation and feeder 10 Nakhonnayok substation. And the operations are being taken at present.