Protection schemes for distribution lines in DC power grid

DC distribution network will be widely used in the future with more integration of distributed generation. However, development of DC distribution is hindered by lack of appropriate circuit protection technologies. Certain protection schemes are studied in this paper, and used to detect and isolate the fault on the distribution lines and bus-tie line. The instantaneous overcurrent protection and the near-terminal current variation protection are configured as primary protections to guarantee the quickness, and the time-delay overcurrent protection, together with the remote-terminal current variation protection work as backup protections to ensure the protecting zone. An instantaneous value-based differential current protection is designed for bus-tie line due to its short length. Both variation and ramp rate of the current are employed as criteria for fault. A typical radial distribution network is selected as case study, and simulation results verify the reliability and rapidness of the proposed protection scheme.