Abstract :
The paper constitutes an investigation of the operation of protective systems in this country over a period of 5 years, ending in 1933, based on a questionnaire circulated to a number of electricity supply undertakers; and in this survey electrical apparatus has been divided into seven classes: generators, transformers, converters, rectifiers, other plant, busbars, and feeders. By analysis of the operating results of the protective gear installed in conjunction with these various classes of apparatus, it has been found that the degree of protection against damage due to faults is of a high order. On the other hand, continuity of supply is adversely affected by the operation of the protective gear when this has been unnecessary. The degree of unnecessary disconnection varies with different types of apparatus and with different systems of protection. The causes of incorrect operation are divided into two classes: fundamental, and maintenance or installation. On the whole, incorrect operations due to fundamental causes are few compared with those due to maintenance or installation. It is shown that in general, and in the case of feeders in particular, the information contained in the returns was inadequate to enable full conclusions to be drawn at this stage, in particular because of the difficulty in examining returns, owing to variations in nomenclature and in the methods of recording experiences. It is, however, thought that the publication of the data obtained will be of value in stimulating interest and improving co-operation in the further investigation now being undertaken. The paper contains the Protective-Gear Operation Form which has been circulated with the object of eliminating the objectionable features encountered in the examination of the returns made over the 5-year period.
