Fault Characteristic Analysis and A Novel Pilot Protection Scheme for Pole-to-Ground Fault in Flexible DC Distribution Network

Due to the pseudo-bipolar structure of flexible DC distribution network, short-circuit current caused by a pole-to-ground fault is weak. The characteristics, particularly steady-state are not prominent. Therefore, diagnosis and protection have become more challenging. This paper theoretically studies characteristics in derives analytical expression current, analyzes directional characteristics. Then, novel pilot scheme based on direction comparison proposed. compares positive negative half-wave integral values components judge direction. directions both sides feeder obtained through channel, thereby distinguishing internal external faults. simulation results show that proposed can reliably identify faulty has an excellent ability perform with high transition resistance. Moreover, does require sampling synchronization, which easy be applied engineering.