Comprehensive consideration of transient frequency deviations in power-system transient-stability studies

Abstract

Recent studies which have considered separately the influence of transient frequency deviations on the various components of power systems subjected to transient disturbances are integrated, with the resulting development of a comprehensive computer program which takes full account of frequency dependence of all systems components and allows a more complete assessment of system performance than has hitherto been possible, The program can readily incorporate existing refinements of representation. Two realistic power-system problems illustrate the nature and variety of the system behaviour when frequency dependence is included, indicating particularly that overall negative damping may be present in some systems. Even when damping is positive, as is more usual, it may still be unsafe to neglect its influence as, although stability assessment appears conservative, voltage and current distributions in the network are erroneously predicted, and problems may be caused by the protective-relay settings based on these predictions. Although the computing time required to treat a system with full frequency dependence included is substantially greater than that for conventional calculations, the extra calculating cost seems warranted by the increased accuracy of calculation.