Equivalent Circuits for an SLG Fault Distance Evaluation by Curve Fitting in Compensated Distribution Systems

We present an extended zero-sequence equivalent circuit for compensated medium-voltage systems, with load current contribution accounted for in the zero-sequence voltage drop accounts. It opens its application to complete and eventually filtered waveforms, rather than only one frequency component. Consequently, the new zero-sequence circuit adapts more to fault-location tasks both in overhead and in cable systems, particularly in the presence of important capacitive currents, where extraction of the main charging current may be not an obvious operation. We have applied it in curve-fitting procedures for the evaluation of a single-line-to-ground fault distance. Fault resistance, fault position, and inception angle are fitting parameters. Then, the fault position is given with several percent average error, within a 10% untuning range, at small and large inception angles, and for a fault resistance up to 3 kOmega to be compared to the 50-Omega limit achieved before.