Phase selection based on superimposed components

A method is described for faulted phase selection for nonunit-distance protection using the superimposed voltages and currents initiated by faults. Even though superimposed voltages and currents are comprised of many incident and reflected waves it is shown for the first time that the criteria used for phase selection remain valid throughout the fault period. The proposed method is hence very powerful. To demonstrate the potential of the scheme, its response to a number of fault conditions is presented