Power System Fault Analysis

This chapter discusses the problem of power system fault analysis. It presents two distinct approaches. First, it approaches a fault analysis of three-phase systems in the conventional way through the use of symmetrical components. Second, it presents a general approach to the problem of fault analysis. Sequence models can be derived for any three-phase power system element, assuming that it is a symmetric three-phase system. The zero sequence reactance of a synchronous machine is much less than the other reactances. For this reason, a synchronous machine is almost always grounded through an inductor to limit the zero sequence currents through the machine. Three-phase transformers are characterized by series and shunt impedances. The zero sequence network of a three-phase transformer depends on the transformer connection. The chapter discusses short-circuit analysis techniques based on the sequence model representation of power system elements. It then examines symmetrical as well as asymmetrical short circuits, with emphasis on asymmetrical faults.