Ground Potential Rise and Transient Response of the Grounding Grid Based on the Triggered Lightning

Abstract

It is extremely dangerous of ground grid potentials which significantly rise when the lightning currents are flowing through the grid. A statistical analysis on 39 return-strokes, 10 M-components and the ground potential rise (GPR) caused by them based on 7 triggered lightnings is carried out. According to the analysis, the geometric mean (GM) of the current peak values of 39 return-strokes is -12.78 kA, and the corresponding GM of GPR reaches -138.97 kV; the GM of the current peak values of the M-components is -0.60 kA, while the corresponding GM of GPR is -7.18 kV. There are distinct sub-peaks in the waveform of the GPR caused by the return-strokes, and the GM of the sub-peaks falls to -90.09 kV within several microseconds, about 64.86% of peak values. During the return stroke stage, the linear correlation coefficient of GPR voltages and the direct lightning current is 0.94, and the linear correlation coefficient of GPR voltages and the gradient is 0.55. It indicates that the GPR in return stroke stage is mainly caused by lightning current discharge in soil and the inductive coupling is relatively weaker. During the M-component stage, the correlation coefficient of peak value of GPR voltages and direct lightning current reaches 0.99, which means the GPR during M-component stage is mostly caused by lightning current discharge in soil. The impulse grounding resistance in the stage of return stroke when lightning current dispersing through grounding grids is 10.87 Ω, and it is 12.02 Ω in the stage of M-component. Both of the impulse grounding resistances are smaller than the DC grounding resistance, and the difference reaches 1.1 times. The minimum half-peak width of the GPR caused by the return-strokes is 0.44 μs, of which the GM is 1.93 μs, only 25.8% of the half-peak width of the corresponding current return-stroke. And the half-peak width of the GPR caused by M-components can be up to 2 microseconds, about 124 times of the GM of the half-peak width of the return-strokes, keeping the surge protective devices (SPD) running long which easily leads to crashing damages.

Keywords

• triggered lightning
• ground potential rise
• return stroke
• impulse grounding resistance