Fast and reliable DC fault detection is one of the key techniques to break through for multi-terminal flexible DC grid. According to the characteristics of the DC reactors on the line

a novel boundary protection scheme is proposed to quickly detect the fault line using the voltage magnitude and direction of the DC reactors. And the fault type and fault pole can be judged with the difference in the voltage of DC reactor between the positive and negative poles of the fault line. The scheme can provide fast DC fault detection and identification just by the voltage of the single-ended DC reactor

thereby meeting the protection requirement of the DC grid while simplifying implementation. For the local fault detection of the proposed scheme

no telecommunication is needed. A three-terminal flexible DC grid model is built in PSCAD/EMTDC for simulation results to demonstrate the effectiveness of the scheme proposed under different DC faults and operating conditions.