Distribution System Short Circuit Analysis

Abstract

The computation of short circuit currents for unbalanced faults in a normally balanced three-phase system has traditionally been accomplished by the application of the method of symmetrical components. However, this method is not as well suited to a distribution feeder that is inherently unbalanced. For example, it is important to be able to compute line-to-ground faults that occur on phases b and c and line-to-line faults that occur on phases other than just b and c. This paper will develop a method for computing all combinations of fault currents using the phase frame of reference. A sample system will be used to demonstrate the method.