Transient theory of synchronous generators connected to power systems

Practical methods of predetermining the transient performance of synchronous generators have in the past been based more on general considerations than on a strictly logical theory. On the other hand, general equations for the synchronous machine were derived by R. H. Park and are well known, but the equations have not been widely used in practice because a direct solution is laborious. The paper shows how, by making a number of approximations, simple solutions of the equations can be obtained for short-circuit and other fault conditions, both for the generator by itself and when it is operating with an external power system, assuming the circuits to remain balanced. The formulae obtained for the transient reactances and time-constants agree, in the main, with those deduced from general considerations. The present treatment, however, demonstrates clearly what are the underlying approximations, and shows what simplifications can be made when some of the components of the transient currents can be neglected.