A new phasor estimation method for digital protective relays

Faults and maneuvers in the system may trigger undesirable voltage and current waveforms of non-fundamental frequency that may affect the performance of protection and control systems. In this context, the proposed method aims to improve the characteristic of filtering out undesirable frequency components of signals. Comparisons are made in relation to time response and frequency response for the proposed method and four classical phasor estimation methods. A distance relay was implemented by using the MODELS language of the ATP (Alternative Transients Program) in order to evaluate the relay performance. As expected, for the proposed method, the relay exhibited good performance in terms of accuracy. In terms of relay speed, the method showed a performance comparable to that of the other methods. Theoretically, the phasor estimation proposed method here has a better frequency response than those of the four used methods. Besides, it has a response time fully compatible with these methods. Another advantage of the proposed method is that it can be easily programmed, allowing users to change design parameters according to their needs.