Estimation methods using dynamic phasors for numerical distance protection

Abstract

In the paper several new methods for faulted transmission line parameters estimation in phasor and time domain are proposed, that eventually improve the overall performance of numerical distance relays. The concept of dynamic phasors is introduced to accommodate the time-variant nature of the current and voltage signals during transients and faults. Based on dynamic phasor transmission line models direct and indirect estimation methods are derived. For proposed indirect estimation method, stability of prediction error dynamics is assured by using Lyapunov direct method. Presented estimation techniques are compared to a conventional stationary phasor solution as well as to a recursive least-square (RLSQ) estimator derived in the discrete time domain. In the evaluation, more realistic assumptions are considered as regards distortion of input voltage and current signals along with the variable fault resistance due to the arcing faults. Simulation results and actual field measurement are included for performance evaluation of proposed estimators.