A new least squares error based method for accurate phasor estimation of fault currents in series-compensated transmission lines

•The transient component of fault current is investigated in series-compensated transmission lines in detail.•A new method based on least square error (LSE) is presented to accurately estimate the principal component phasor of fault current.•The performance of the proposed method is investigated under different operating conditions.•The proposed method can precisely track the fundamental power frequency in off-nominal conditions.•The proposed method is immune to noise up to an SNR value of 30 dB.•The promising results show that the proposed method can be effectively used for fault-locating applications. Phasor estimation of the fundamental component of the fault current is of great importance for the fault location unit in distance relays. In series-compensated transmission lines, the transient component of the fault current may appear in the complicated wave shape of an exponential-sinusoidal function. Thus, phasor estimation is a major challenge owing to the fact that more unknown parameters should be found, especially during off-nominal frequency conditions. Therefore, in this paper, a new method is put forward, on the strength of the least squares error (LSE), in order to accurately estimate the fundamental component phasor of the fault current in a series-compensated transmission line for off-nominal frequency conditions. The performance of the established method is also investigated through extensive simulation studies, taking care of different fundamental components, harmonic contents, and transient components. Moreover, the performance of the proposed method is evaluated for off-nominal frequencies. The results obtained in this study demonstrate that the mean absolute error of the estimated amplitude and phase for the fundamental component is less than 1% and 1°, respectively. Furthermore, the accuracy of the proposed method is not affected by the noise up to a signal-to-noise ratio of 30 dB. Thus, the established method is capable to effectively be employed for the phasor estimation in fault location applications.