Short Circuit Study Incorporating Phase Shifting Components

A complete and comprehensive mathematical model of phase shifting components is developed using a delta-wye transformer bank as an example of a typical phase shifting component. Linear graph theory techniques are used to form the model which is called a V-equivalent. The V-equivalent is incorporated into the network matrix called ZBUS which is then used in the short circuit equations for a line-to-ground fault. In this paper, a numerical example utilizing a sample power system is used to illustrate the method by which the V-equivalent of a delta-wye transformer bank is incorporated into a digital computer program for short circuit studies. The results of the digital computer program demonstrate that, by the use of the V- equivalent, phase shifting components such as delta-wye transformers can be made an integral part of the power system model. A single line-to-ground fault can occur on either side of the delta-wye transformer bank, and the correct values of the currents and voltages at the fault and throughout the system can be obtained directly from the solution of the system model. No subsequent calculations are necessary to correct for the effect of the phase shift.