Calculating the Number of Lightning Induced Outages of a Double-Circuit 110 kV Overhead Power Line

The voltage surges in a double-circuit 110 kV overhead power line are analyzed using the methods of grounding theory, and the probability of insulation back flashovers is quantified using the dangerous currents method. The article proposes a new approach to the choice of calculated lightning strike points – in the overhead ground wire at a distance of a quarter of a span. In the frequency-dependent high-resistance soil model recommended by the CIGRE standard, the grounding conductor pulse impedance is less than the stationary one, therefore, voltage surge levels at the pulse front decrease, and insulation back flashovers occur during pulse decay. The expected number of lightning outages of a 110 kV double-circuit overhead power line does not exceed the average operating values with a grounding rods resistance of up to 15 Ω. A typical four-leg grounding device (with legs up to 60 m) satisfies the specified resistance in the soil with a resistivity of up to 1500 Ω·m. If its resistivity is higher, it is recommended to strengthen the tower grounding systems with a counterpoise grounding device, hang a second overhead ground wire under the overhead power line wires, or lay it on the ground surface. Means for protection against double–circuit overhead power line outages, namely, increasing the number of insulators in one circuit and installation of line surge arresters, are studied.