Comparative analysis of fault resistance compensation methods for mutually coupled parallel transmission lines

Most of the existing overhead transmission lines are operated in parallel configuration. These transmission lines are protected by the distance protection scheme with the help of distance relays. The impedances measured by the distance relay are affected by the mutual coupling between the lines and the fault resistances. In this paper, the impact of mutual impedance between parallel transmission lines is studied and different algorithms to compensate fault resistances are examined and compared. A distance relay protection scheme is analysed to overcome the drawbacks of zero sequence mutual impedance and fault resistance during a single phase to earth fault. The simulations have been done in PSCAD. Phasor estimation is performed in MATLAB using the full cycle recursive DFT (Discrete Fourier Transform) algorithm. Phasors thus obtained are used for the calculation of fault impedance.