Transient overvoltages on power systems

Power systems are subjected to many forms of transient phenomena brought about essentially by sudden changes in the steady state values of voltages or currents. Such changes may be the result of a lightning stroke, some malfunction of the system or be brought about by the switching of a circuit either to clear a fault or as a normal operational procedure. To be practical the scope of the review has had to be restricted. Nevertheless it has been found possible to cover a wide range of transient voltages from those which pose problems in transmission systems operating at the highest levels of system voltage down to those which can appear in the domestic situation. Apart from mentioning nonlinear elements in systems, the review is, in the main, restricted to phenomena which are essentially linear in nature and no attempt has been made to include the more complicated phenomena associated with ferroresonance or the production and propagation of harmonic voltages and currents. The review does not claim to be exhaustive but it is hoped that the major causes of transient overvoltages have been considered. In addition to dealing with the causes of transient overvoltages, the review indicates the range of analytical methods that are now available for their analysis and assessment.