Protective Gear on Power Supply Systems

Abstract

AN interesting paper entitled “The Management of Protective Gear on Power Supply Systems”, read recently in London before the Institution of Electrical Engineers by W. Casson and F. H. Birch, of the Central Electricity Board, discusses the theoretical and practical considerations affecting protective-gear engineering. After reviewing the responsibilities and qualifications of protective-gear engineers the authors investigate a number of typical system fault conditions, giving methods of calculating fault currents and voltages, the relations between which are illustrated by vector diagrams. System abnormalities other than faults are discussed and attention is directed to their relation to protective-grear operation. The performance and correct application of protective gear are stated and a general outline of the work of commissioning the gear is given according to the type in use. Testing methods and testing equipment are described and consideration is given to protective-gear troubles and routine maintenance procedure. Finally, the paper discusses those features of protective-gear design, construction and layout which assist maintenance. The paper is based upon experience obtained during the last ten years with protective gear installed on the Grid system in Great Britain which, while having been designed primarily for peace-time fault conditions, has been found to give an overall fault performance of 92 per cent correct in 1940 when, due to war-time hazards, operating conditions were exceptionally severe.