Performance enhancement of digital relays for transmission line distance protection

This thesis investigates the performance enhancement of digital relays for transmission line distance protection from filtering (extracting the fundamental frequency components) point of view and relaying algorithm point of view. -- Several Fourier based filtering algorithms are investigated, simulated, and compared in this thesis. Furthermore, a new wavelet transform based real-time filtering algorithm is proposed. The studies suggest that this method converges faster than Fourier based algorithms. -- Two types of relaying algorithms are also examined in this thesis. One algorithm, which compensates the fault resistance, only needs to monitor the voltage and current signal at the relay end. The other algorithm makes use of the information from both ends of the transmission line and adaptively adjusts the relay operating characteristics. Both theoretical analysis and simulation results show that these algorithms can significantly enhance the performance of digital relays for transmission line distance protection