Analysis of the Influence of the Earthing Resistance of Pylones on the Performance of the HVAC Line Facing Electromagnetic Transitories Lightning

Abstract

The roles of electrical energy no longer need to be demonstrated since the industrial revolution of 1740 based on the use of new sources of energy, of which electrical energy is considered to be one of the greatest revolutions in the world. Despite this, we must note that electrical energy is changing the habits of human activity and, on the one hand, has consequences on its transport, the large quantities of which are transmitted by power lines, forcing them to operate more and more. more within their limits and unplanned outages increase the risk of instability. Storms, industrial pollution, and lightning strikes are the main causes of these unscheduled outages. In regions with a high keraunic level, the reduction of insulation breakdown due to lightning is, therefore, a major concern for designers and operators of HV lines. It is possible to reduce the number of tripping of power lines due to lightning by the proper installation of ground wires and by the appropriate grounding of pylons. In this article, we focus our research on the analysis of the impact of the earthing of the pylons on the performance of HV lines against lightning strikes. Considering these parameters and using the oldest and simplest analytical model as a time-varying current wave whose model is a difference of two decaying exponentials, we brought into contribution Maxwell's equations, the law of Ohm, telegrapher's equations, transmission line theory, and the FDTD method to model lightning-induced voltages as a function of HVAC tower grounding. This study was carried out on the Liminga-Funa 220 kilovolt alternating line in the DRCongo, located in a region where storm activity and industrial pollution are very high. Thus, the results obtained by simulation show that the peak voltage on the components of the HVAC line is a linear function of the impedance of the earthing of the pylon. The impedance value of the pylon earthing less than or equal to 10 Ohm dampens the atmospheric overvoltage and ensures good coordination of the insulation of the line elements in the event of a lightning strike at the top of the pylon for the first bow. But for the return arc taken in this case, the bypass of the insulator is unavoidable. The fractal dimensions of the results of our programs have been compared with those of the figures obtained experimentally.