| Summary: | Adaptive reclosing of AC line discriminates temporary faults and permanent faults by the coupling relationship between fault phase and the sound phase. While in the DC network, the electrical quantity of the DC system keeps constant after the DC line fault is cleared, and there is no coupling relationship between the sound and fault pole. This paper presents a fault identification method by injecting characteristic signals into a DC fault line. The electrode coupling characteristics of HVDC transmission lines, the injection method, and the selection of characteristic signal are given in detail. Then, the characteristic signals are injected into the sound pole through the additional control strategy of the converter station. As of electrode coupling characteristics of transmission lines, the fault line induces the coupling characteristic signal. This characteristic signal on the fault line is used to distinguish the fault property by the differences of the propagation feature between the two states, the fault existence and disappearance states. The simulation results verify the effectiveness of the method here.
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