Lightning performance of British high-voltage distribution systems

On the basis of some 80,000 supply-interruption reports, supplied by Area Boards over a period of ten years, the lightning performance of British high-voltage systems is investigated, with particular reference to 33kV and 11kV systems. The frequency of supply interruptions and its annual variation are examined as a function of line construction and thunderstorm activity, and the efficacy of arc-suppression coils is determined. Rates of failure of high-voltage equipments are evaluated. Special attention is paid to transformer failures, and to the protective effects of surge diverters and spark gaps. Close contact was maintained throughout this investigation with all Area Boards, and some of the more general recommendations which have been put into practice are mentioned.