Distance protection based on an adaptive window length filtering algorithm

Filtering algorithms estimate the impedance of discrete distance protection by estimating the fundamental voltage and current phasors at the relay location. These phasors are estimated by correlating currently and previously sampled voltage and current signals with sine and cosine functions. Standard filtering algorithms have data windows corresponding to one cycle of the power frequency and corresponding tripping times. Shorter fault detection times can only be obtained by decreasing the data window length. This, however, compromises the security or the maximum reach of the first zone of protection of the distance protection scheme.; To obtain the speed associated with short data windows and to retain the security associated with full cycle windows, an adaptive window length phasor estimation combined with a variable trip area is proposed in this dissertation. The phasors are initially estimated by two point phasor estimators. The filter length is increased after fault inception until it reaches a full cycle, always assuring that only the post-fault data are used. The trip area is initially set to a relatively short reach, enabling the relay to detect close faults with high speed. The trip area is slowly increased with increasing filter length until it reaches its maximum reach for full cycle estimators. Consequently, the relay retains the security of full cycle filtering algorithms and detects close faults more quickly than full cycle filtering algorithms.; The fault resistance of ground faults can affect the inductive reactance estimation and thus can depreciate the reliability of standard distance algorithms. The proposed algorithm includes a method to compensate errors in the reactance measurement. This enhances the reliability of distance protection. This method utilizes the pre-fault positive sequence current.; Distance protection can respond insecurely when protecting series compensated lines with the capacitor installed at the bus side and the relay voltage measured at the line side of the capacitor. Then, an additional sequence directional element can provide the necessary security. This dissertation also contains a study of the performance of positive and negative sequence directional elements on MOV protected series compensated transmission lines.