System overvoltages caused by faults and switching

Power system overvoltages may result from lightning, switching, faults, loss of load, and other causes. An understanding of the phenomena associated with all causes of overvoltages is necessary to control the magnitude and to co-ordinate the protection and insulation levels of the system. Lightning may be considered the chief source of high overvoltages. Much attention and study has been and continues to be given to all lightning phenomena and means of protection. Next and of increasing relative importance are the overvoltages produced by faults and switching surges. Considerable study has been given this subject during the past 25 years and it is opportune to review the literature on power system overvoltages produced by faults and switching surges which includes results obtained from field tests; the phenomena that control cumulative oscillations and restrikes; and the results obtained by the miniature system of analysis which show the influence of grounding, arrester location, and circuit breaker interrupter restriking. Such a review prompts a number of conclusions which indicate the progress and understanding of the subject to date and which also may serve as a guide to future investigations.