Моделирование и анализ молниезащиты при нештатной ситуации удара молнии на электрической подстанции

Abstract

The grounding of the supports determines the resistive, the most significant component of the overvoltage acting on the insulation gap between the lightning rod and the equipment of the electrical substation when lightning strikes the lightning rod. (Research purpose) The research purpose is in developing recommendations for the grounding devices for lightning rod supports and means of suppressing sliding spark channels in a multi-wire system. (Materials and methods) The estimation of the share of lightning current in the grounding conductor of the lightning rod support can be calculated simplistically. This makes it possible to abandon the solution of long-line wave equations and switch to a substitution scheme with concentrated parameters, in which the active and inductive resistances of sections of an electric circuit loaded with lightning current should be considered, with mandatory consideration of inductive connections between them. (Results and discussion) The article presents the calculation for a pulse with an oblique front and a flat head, which is traditionally used to estimate the number of reverse overlaps on an overhead power transmission line when a lightning strike hit a support. It was assumed that the lightning strike occurred in the extreme thunderstorm, the current load mode of which is the least favorable. The greatest current load of the grounding conductor of the support corresponds to a direct lightning strike, when the current amplitude there differs from the current amplitude of the first component in the lightning channel by no more than 25 percent, this mode should be taken as the calculated one when estimating the maximum length of the sliding spark channel. (Conclusions) The maximum lengths of sliding spark channels in soils of different conductivity were determined using computer modeling of an emergency situation of a lightning strike, provided that the reinforced concrete foundations of the lightning rod supports connected by an underground horizontal bus are used as grounding conductors of lightning rods. The most effective means of limiting the danger of sliding spark channels is their forced orientation to the side, which is safe for the grounding circuit of an electric substation.