ABSTRACT
The use of electricity brings with it an electric shock hazard for humans and animals, particularly in the case of defective electrical apparatus. In electricity supply systems it is therefore a common practice to connect the system to ground at suitable points. The value of resistance to ground of an electrode system is the resistance between the electrode system and another "infinitely large" electrode in ground at infinite spacing. A common method for obtaining a low ground resistance at high-voltage substations is to use interconnected ground grids. The resistance to ground determines the maximum potential rise of the grounding system during a ground fault. Scale model tests with an electrolytic tank are very useful for determining the ground resistance and surface potential distributions during ground faults in complex grounding arrangements where accurate analytical calculations are hardly possible. The chapter discusses new methods which have been proposed to decrease ground resistance: Cracks with Low-Resistivity Materials, Grounding Augmentation Fill and Fall-of-Potential Method.
