The cost and efficiency of earthing on low- and medium-voltage overhead line systems

After describing the scope of protective earthing and the various methods available, the paper sets out a method by which the amount of protection afforded by each method may be evaluated from a knowledge of the incidence of those types of fault which contribute to the risk of shock. The cost of applying each method is established, and risks are calculated on the basis of available information of the incidence of faults. The systems are then compared on the basis of the amount of protection afforded for a given expenditure. Recommendations are made for the alleviation of the conditions under which protective multiple earthing may be utilized in Great Britain.