Environmental impact on the insulation of 10 kV distribution power lines

Outdoor insulation of 10 kV overhead distribution lines with wooden and concrete poles has been studied under various environmental conditions including contamination, moisture condensation, rain, and lightning overvoltages. It has been shown that the absolute value of the resistive leakage currents may exceed capacitive currents in the same network under both normal and emergency operating conditions. The minimum value of the resistive current that may result in the ignition of wooden poles has been determined. The development of the lightning flashover into a steady electric are has been studied experimentally. The magnitude of the arc current has been related to the durability of the line insulators. Time-voltage characteristics of the surface and volume breakdown of porcelain and glass pin insulators have been studied. It was shown that the lightning stroke leads, with high probability, to the electrical puncture of dielectric material. The remaining electrical strength of the punctured insulator has been evaluated. It has been shown that the insulators may remain in service after the initial puncture for up to 5 years on reinforced concrete poles and for even longer periods of time on wooden poles. The methodology for protection of the wooden poles from the ignition due to lightning induced currents and leakage currents is proposed. The recommendations are made regarding the choice of the material for the support poles that work in different pollution and humidity environments