Horizontal Electric Field in the Vicinity of Structures Hit by Lightning

Abstract

Abstract:The horizontal electric field at the ground surface in the vicinity of structures hit by lightning flashes is relevant to the safety of human beings and livestock; it determines the touch and step voltages around the structure. This paper uses an approximate analytical formula for calculating the horizontal electric field, which was adapted to take into account the effect of the structure foundation. The input for the calculation is the current waveform at the base of the structure, and the results agree well with those obtained by other authors using the finite-difference time-domain (FDTD) method. The approximate formula is applied to calculate touch and step voltages in the vicinity of a structure and the results show that the use of the direct current (DC) approximation to calculate touch and step voltages may lead to significant errors; especially for fast-rising currents and relatively good-conducting soils. This means that DC approximation could be used for positive first stroke and poor-conducting ground (ρ ≥ 1000 Ω·m), but cannot be used for subsequent strokes and good-conducting ground (ρ ≤ 100 Ω·m). Moreover, step voltages differ more from the DC approximation than the touch voltages.

Simulation and Optimization of Electrical Insulation in Power Quality Monitoring Sensors Applied in the Medium-Voltage

“…The equipotential line has a value exact in the region between the cylinders because the electric field in this region is constant and uniform while the equipotential in the hemispheres region has a value approximated because the electric field is non-uniform. As shown in [20], the equipotential surface tends toward a hemisphere and by heuristic approach this is a good approximation.…”