Electrical Engineering Section, Indian Institute of Science, Bangalore-12.
It is very essential to determine at least approximately the resistance of the grounding arrangement before actual installation. Resistivity value used for the calculation of resistance is often the source of error of considerable magnitude. Resistivity value obtained is a function of probe spacing. The problem is to choose a resistivity value such that the calculated resistance will be approximately equal to the measured resistance.
A solution is outlined in this paper when the grounding system consists of a single driven rod. Field tests have been carried out to establish a relation between the probe spacing and the length of a driven rod. The chief conclusion of this investigation is that by choosing a probe spacing corresponding to the length of a driven rod, the calculated resistance will be approximately equal to the measured resistance.
The average value of resistivity to various depths was explored at three different places by expanding the probe spacing.
