A sensitivity method for assessing the impact of generator/transformer impedance on power system fault behaviour

An analytical method is presented for determining the potential impact that the connection of a single new generator may have upon the performance of a transmission system under balanced three-phase fault conditions. Expressions are derived that demonstrate the dependence of the system-wide fault behaviour of the modified network upon both the sub-transient or short circuit impedance of the new generator/transformer and the configuration of the original network. From these expressions sensitivity factors are developed that characterise the potential impact that the connection of the new generator can have upon network fault behaviour. The procedure is derived in general terms and verified with results from simulation of a 17-bus test system. The results emphasize that the impact of the generator/transformer is often more contingent upon the network characteristics at the point of connection rather than the subtransient/short circuit impedances of the new elements.