Digital protection of transmission lines using a new phasor measurement approach

The paper presents an improved Gauss-Newton approach for fast and accurate estimation of voltage and current phasors, which are a prerequisite for distance relaying applications. The improved Gauss-Newton method has an advantage that the fundamental voltage and current phasors are estimated accurately even in the presence of decaying dc, harmonic components and measurement noise. The proposed algorithm has been applied for the protection of a transmission line fed from one end both with and without transformer saturation; the ensuing R-X trajectories clearly reveal very fast operation. Hence, very accurate fault location estimation can be made by utilizing this new approach.