Lightning surges on transmission lines in Ireland

A brief account is given of an investigation of lightning disturbances on the Electricity Supply Board's system in Ireland. Figures for the average lightning faults per 100 miles of line per annum for the 110-, 38- and 10-kV systems are derived from a 10-year record of such faults. Using the records of the 10-kV system as a basis, the author constructs a map showing the variation of lightning trouble intensity for different localities in Ireland. An account is also given of some magnetic link observations of lightning surges on the earth leads from 110-kV overhead earthwires and from 38-kV lightning arresters. The results obtained appear to show that a large proportion of the discharge currents of such arresters have values below 1 000 amp. Since the usual practice has been to mount magnetic links so that only currents in excess of about 3 000 amp are recorded, it would seem that many arrester operations may have escaped detection, and the results of such observations could therefore lead to erroneous conceptions as to the frequency of operation of medium-voltage arresters. Since modern lightning technique is largely a question of the economics of individual applications, the author stresses the importance of obtaining adequate local lightning data wherever possible.