This paper proposes a new principle of HVDC protection on two-terminal electrical quantities. Based on the analysis of short-circuit faults on different locations, it is found that as for current and voltage variation, there is a large difference between internal and external faults. According to this, the product of rectifier and inverter DC current variation can be used to distinguish the internal and external faults except for opposite pole line faults. In order to distinguish which DC line occurs short-circuit faults, bringing in rectifier and inverter DC voltage variation can achieve the target. This method identifies fault types quickly and has great tolerance of transition resistance. By building a HVDC model on PSCAD/EMTDC, the applicability of faults on different locations can be tested. The simulation result proves that the method has high reliability and can be applied to the whole line.
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