Abstract :
After describing the development of the ratings of switchgear for voltages above 100kV during the last few years and indicating the current trends, the paper considers the more important special conditions for which modern switchgear has to be designed. A brief account is given of the present state of the theory of circuit breaking and of the research now being conducted, together with a review of the switchgear testing methods and stations now in operation. The principles of the more recent developments in the design of circuit breakers, isolators, switches, instrument transformers, surge diverters, fuses, insulators and the layout of substations are illustrated by examples from British and foreign practice. An indication of possible developments in totally enclosed switchgear for high voltages and in the switching of high-voltage direct current is given.
