An analysis of supergrid transmission fault data in a specific area of England and Wales

The CEGB have developed a Monte Carlo simulation program to assess the risk of multiple outages of high voltage electrical transmission circuits, which forms a part of the general risk assessment for nuclear power stations. This paper reports the results of an analysis of 13 years' data for the South West area of England and Wales. Normal and adverse weather states are encompassed and common mode and cascade failures are investigated, but the major topic is the analysis of the distribution of component fault repair times using the REGINA:82 program. It is concluded that the lognormal distribution provides a better fit to the observed repair times than either the exponential or Weibull distributions. The implications of this conclusion are discussed and the results of this study are compared with previous analyses.