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Multi-Function Protection Scheme for HVDC Transmission Systems

In this paper, a protection scheme for HVDC systems is proposed covering both line and busbar faults. To increase the scheme reliability, the detection criterion depends on multiple detection functions based on the pole currents and busbar voltage together. Then, a voting algorithm is utilized to issue a tripping decision based on the majority of the results of the applied protection functions. The scheme is installed locally at each busbar and it can detect and disconnect the faulted line without communication links with other terminal. Moreover, the scheme can detect high impedance faults (HIFs) for the pole to earth conditions. In addition, the scheme can discriminate the fault type as either a pole to pole or pole to earth fault. This increases the service continuity by facilitating transmitting half of the rated power through the healthy pole. For investigation purposes, the proposed scheme is evaluated with a two-terminal HVDC system. Different simulation cases are evaluated with a variety of fault conditions using Matlab/Simulink. The results confirm the reliability, security, and efficacy of the proposed protection scheme for providing a protection for the HVDC transmission systems.