Single-Ended Transient Protection of HVDC Transmission Lines Based on Multi-Resolution Morphological Gradient and Morphological Entropy

The application of HVDC transmission technology in power systems is increasing rapidly while the currently used protections for HVDC systems operate on the principles which have poor reliability and inadequate sensitivity. To overcome these problems, a new single-ended transient protection scheme is proposed. Due to the boundary characteristics of the HVDC transmission line, the high-frequency entropy of voltage signal is significantly reduced that when passes through the boundary. According to the difference of high-frequency morphological entropy, criterion to distinguish between internal and external faults and between fault and sound poles can be constructed. Morphological filtering is used for singular point detection to construct startup criterion. Based on the PSCAD/EMTDC electromagnetic transient simulation platform, a simulation model of a ±500kV DC bipolar transmission system is established to test the effectiveness of the proposed scheme. Various internal and external faults with different positions and different transition resistances are simulated considering noise interference. Simulation results show that this scheme can reliably identify internal and external faults with robustness to high resistance and strong anti-noise ability.