Probabilistic Aspects of Transmission System Switching Surge Reliability

Probabilistic principles are applied to predicting the transmission system flashover rate caused by switching operations by combining results of laboratory tests on component insulation structures with system overvoltage probability distributions. A piecewise normal method is developed, applicable when statistical dependence of insulation structure flashover and system over- voltage generation cannot be described by standard normal distributions over the entire specified range of voltages. Results are obtained for large numbers of insulation structures in parallel and, by appropriately synthesizing the described sub-systems, entire transmission systems can be analyzed. The effect of voltage limiting devices, such as arresters, has been studied and their effect on system performance can be included in the analysis.