Design Consideration of the Shielding Wire in 10 kV Overhead Distribution Lines Against Lightning-Induced Overvoltage

This paper presents a systematic investigation into the performance of a shielding wire on 10 kV overhead lines (OHLs) against indirect lightning, from the design point of view. The design parameters addressed include the grounding interval, grounding resistance, and position of the shielding wire. As a system outage is usually caused by insulator flashover at OHL poles under indirect lightning, the induced voltages there are investigated with the code developed from the Agrawal model. In the evaluation, the location of a lightning return stroke relative to a grounded or ungrounded pole is considered. It is found that the lightning channel positioned in the front of an ungrounded pole could completely wipe out the effect of the shielding wire. This occurs if the wave from the grounding point arrives later than the time to the peak of the voltage directly arising from the lightning return stroke. It is suggested providing the wire grounding at every pole even if the grounding resistance at some poles is much higher than the design value. Grounding spacing does not affect the induced voltages at the pole generally if the pole has been grounded. One critical parameter is identified, i.e., the distance between the shielding and outer phase wires. Minimizing the distance can effectively reduce the lightning-induced voltages.