Impedance estimation including ground fault resistance error correction for distance protection

A distance protection scheme, which uses phasors of symmetrical components not only for supporting features but also for the core function of the distance calculation, is described in this paper. The sequence current and voltage phasors are numerically efficiently extracted from the phase quantities by two Clarke and three discrete Fourier transformations. A fault resistance during ground faults can depreciate the reliability of standard-distance protection algorithms. The described algorithm includes a method to compensate errors in the inductive reactance measurement caused by the ground fault resistance. This enhances the reliability of the distance protection scheme for faults around the remote-transmission line end. Simulation results demonstrate the performance of the proposed protection algorithm.