Effect of the mutual inductances among grounding conductors on the transient performance of grounding grids

In this paper, a numerical model is presented to analyze the grounding grids. The effect of the mutual inductances among grounding system conductors on the performance of the grounding grid is investigated. It can be seen that although the effect of the mutual inductances is very small at power frequency, when a large grounding grid buried in soil with low resistivity is analyzed, the effect of the mutual inductances should be taken care of even the frequency is not very high. What´s more, when this kind of grounding grid is stricken by a 30 kA 2.6/40 mus lightning current, if the mutual inductances are neglected, although the waveform of the transient potential at the current injected point is almost the same with that considering the mutual inductances at the rise time, it falls more slowly than that considering the mutual inductances.