Abstract :
The method of measuring an earth-electrode resistance has been known for a number of years, but there are some aspects of the measurement which are not fully understood. In particular, there are difficulties which arise when the earth-electrode system is of large physical dimensions, e.g. that of a substation or power station. The simple method which is normally used cannot be applied directly for several reasons. It becomes very difficult to get outside the potential-gradient area of the system, owing to the great distance that it may extend. The auxiliary electrodes used must be placed as far away from the system as is practicable, and this involves the use of long leads, which may possess considerable self and mutual impedance. Again, with these large distances, the stray potential difference in the earth due, say, to leakage from the supply may be considerable, and the measuring equipment used must be capable of dealing with this. After an analysis of the basic factors involved, the paper describes a method of determining the resistance of a large electrode system and apparatus suitable for making the measurement.
