Problem of Measuring Grounding Resistance in a Pulse Mode

Problem of Measuring Grounding Resistance in a Pulse Mode

Ток лабораторного генератора - Laboratory generator current
Ток молнии - Lightning current
Номер заземляющей шины - Grounding bus number

It is much easier to say than to do something. This is applicable to pulse characteristics of grounding devices fully. Even in a concentrated scheme located on a mounting table or in a laboratory, we can find many error sources during pulse measurements. Thus, what can we say about a grounding device having an area of several thousand square meters!

This section describes measurements of the grounding resistance upon the lightning current flowing because they are the most significant problem. We have to start with the fact that the lightning is a peculiar current source. It has no return line. By flowing along the plasma channel into the lightning arrester and then to grounding electrodes, the lightning current goes to "infinity" by flowing across the volume of the Earth having the radius of 6,400 km. In any measurements, we have to simulate the lightning current with some pulse generator that has a return line. The magnetic field from this line will distort the pulse current distribution among the grounding electrodes due to the magnetic induction electromotive force. Such re-distribution will change the measurement results. We are talking about errors of at least an order of several dozen per cent.

Read article by prof. E.M. Bazelyan "Pulse Grounding Resistance" for more details.

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