Analysis of Overvoltages in a 110 kV/MV Substation as a Result of Lightning Discharges to the Overhead Line

The reliability of electrical power transmission and distribution systems depends on progress in the coordination of insulation, which depends, among other things, on increasing the ability to identify risks of overvoltages in insulation systems. The purpose of the paper is to present the problems related to the overvoltages of the power system caused by lightning. The article analyses two possible scenarios of sources of these disturbance: shielding failure and backflashover phenomena. The first case concerns the situation when, despite the ground wires used, it is possible to discharge into the phase conductor. The second case concerns the situation of loss of electrical strength of the insulation system used. The aim of the paper is to analyze the possibility of damage to station equipment as a result of lightning to the elements of the overhead line supplying the 110 kV/MV station. For this purpose, overvoltages levels in 110 kV substation will be determined for characteristic peak values of lightning currents: Imax and Imin - respectively for scenario of shielding failure and backflashover phenomena. Between the Imax and Imin values, we assume lightning protection (lightning strikes to ground wire). The calculations were carried out on a selected fragment of the real 110 kV power system. The simulations were performed using The Electromagnetic Transients Program - Alternative Transients Program (EMTP-ATP) and Matlab.