Estimation of the Overvoltage Induced on a Transmission Line by a High-Current Intracloud Lightning

The study presents estimations of the overvoltage induced on a transmission line by a high-current intracloud lightning discharge. Intense current pulses with amplitudes of up to dozens (in rare cases hundreds) of kiloamperes and durations of the order of 10 μs can be generated by either compact intracloud discharges or initial breakdown pulses. Since their radiation electric field strengths are comparable to that of return strokes, they may be dangerous to low-voltage communication cables and power lines. The numerical model employs the current source as a harmonic dipole and we use the multi-chain equivalent circuit method to calculate the induced overvoltage at different signal frequencies and transmission line spatial orientations. The cases of 10 km long high and low voltage power lines and 100 m long coaxial cable screen are considered. It is found that in most cases the maximal induced potential drop between the transmission line and the ground does not exceed 1 kV or so. However, there are certain frequencies and line orientations at which the induced overvoltage can be comparable with the nominal voltage of most power lines and, therefore, may cause an outage. The development prospects of the model are discussed and possible recommendations concerning protection against the overvoltage caused by a high-current intracloud lightning discharge are proposed.