Abstract
This study presented experimental results of earthing systems under low-magnitude currents and under high impulse currents. The details of the measuring circuit involved for both types of testing were described. Three field sites were selected. At each site, three earth electrodes configurations were used. This makes up to nine earthing systems. From both low magnitude and impulse tests, the correlation between the steady state earth resistance value and the earth resistance under fast impulse currents can be observed. The relation between the calculated and measured steady state earth resistance is also shown in this study.
Highlights
It is known from previous studies that, under high impulse currents, soil non-linearity or reduced earth resistance values versus steady state values are observed[1,2,3,4,5]
Ec magnitudes in the range of 1.3-20 kV cm−1[1,2,3,4] show that the degree of non-linearity or reduced earth resistance values under impulse conditions is not very clear and needs further investigation
It was found that the degree of ionisation in soils is dependent upon the steady state, RDC value; the lower RDC, the lower the ionisation effect on the earthing system under high impulse currents, the impulse resistance becomes less dependent on current magnitudes
Summary
It is known from previous studies that, under high impulse currents, soil non-linearity or reduced earth resistance values versus steady state values are observed[1,2,3,4,5]. It has been found in the literature[1,2,3,4,5] that the magnitude of the electric field Ec, determines the degree of non-linearity and soil resistance reduction.
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