Abstract:
In the DC distribution network, the fault characteristics are complex. The DC fault current rises rapidly, and the peak value is significant. Fast and sensitive fault identification and line protection are the key technologies to ensure the safe operation of the DC distribution network. Thus, a single-terminal protection strategy for the DC distribution network by utlizing current limiting reactor voltage is proposed for the DC distribution network with additional current-limiting reactors, which can sensitively identify faults. Firstly, the characteristic difference of current limiting reactor voltage during internal and external faults is clarified by analyzing the fault characteristics of the DC distribution network with current limiting reactors. Secondly, the influence mechanism of the current limiting reactor on the fault characteristics and DC protection is analyzed in detail, and a virtual compensation strategy is proposed to enhance the sensitivity of fault identification. On this basis, the protection starting criterion is designed according to the change rate of line voltages, the fault identification criterion and fault pole selection criterion based on virtual compensation are proposed, and the complete protection scheme is given. Finally, based on the PSCAD/EMTDC platform, a large number of simulation tests have been carried out. The results show that the proposed protection can achieve fast and accurate fault determination with strong tolerance to transition resistance, noise, and load fluctuations.