Influence of surge diverters on overvoltage probability distributions

The paper considers the effectiveness of modern surge diverters as a means of controlling the overvoltages that occur during switching in power-transmission networks. The requirements and method of realisation of a comprehensive model, capable of simulating the performance of actual high-voltage surge diverters, are discussed. The model is used in an existing transient-network-analyser facility under the control of a small digital computer, and the system has been programmed to perform Monte Carlo testing to determine overvoltage probability distributions. In this way, the sensitivity of overvoltage distributions to variations in surge-diverter characteristics is investigated. The effects of changes in the statistical parameters associated with diverter sparkover and the characteristics of active-gap performance are examined, and conclusions offered in relation to the protective level assured by surge diverters