This publication analyzes the problem of the coupling of lightning and the power transformer in the High Voltage substations of electrical networks during the injection of lightning current to the ground in sites with strong thunderstorm activity, in this case the Democratic Republic of the Congo.Although the aggressive overvoltage induced by lightning is short-lived, its amplitude and frequency greatly disturb the stability in terms of voltage and the continuity of service of the network, especially in its transport part often exposed to open air.During the flow of this shock wave to the earth, through the protection devices (surge arrester) and the earth network, the transient impedance of the substation earth electrode varies suddenly depending on the amplitude of the current flow and the nature of the ground, and reveals around it a potential difference called step voltage and touch voltage, due to the distribution of the electric field, which expose the direct environment of the substation to the danger of electrocution and substation equipment against overvoltage.This publication aims to synthesize the corrector (regulator) which will have to dampen and reject the shock of the flowing current and prevent the potential difference around the earth electrode from reaching deadly values ​​for operators and people residing in the environment close to the substation and facilitated flow through the earth electrode.

To avoid any risk of electrocution and damage to equipment due to an insulation fault or lightning discharge in the HV electrical network consisting mainly of HV transmission stations and lines, all equipment in these energy infrastructures must be earthed through an earth electrode which must maintain its performance over time following the recurrent flows of the shock wave.As this aggressive discharge flows to the ground, the resulting thermal effects can lead to ionization of the soil and reduce the performance of the earth electrode by changing the characteristics of the soil. This publication aims to establish the cause and effect relationship between the thermal effects due to the injected lightning current and the electrical characteristics of the ground through its resistivity.This analysis will allow energy infrastructure designers to take into account these performance changes when injecting lightning current and properly size the earth connections of HV substations.