Evaluation of the Effect of Power Circuit Breaker Reclosing Practices on Turbine-Generators Shafts

Several circuit breaker reclosing practices following transmission system electrical faults are evaluated, and recommendations presented, that minimize the fatigue duty on turbine-generator shafts, while still maintaining the commonly considered advantages of high speed reclosing (H.S.R.). Probability distributions were created for appropriate parameters, so that the statistical nature of high speed reclosing could be treated by Monte Carlo simulation. These include distributions for the timing of opening and reclosing of circuit breakers, the type and location of the fault, the timing of the fault relative to the position on the voltage wave, and the scatter in shaft torsional fatigue properties. For each reclosing practice analyzed, and for each of several turbine-generator designs, the probability distribution of shaft cumulative fatigue expenditure was estimated, based on a forty year fault exposure period, and on an assumed electric system model. These data give a meaningful basis for comparing different types of reclosing practices that are presently in use. This paper advances the state-of-the-art by being the first to apply statistical methods to the analysis of this subject.