1.School of Electronic Information,Xi’an Polytechnic University;2.School of Electrial Engineering and Automation, Hefei University of Technology;3.State Grid East Inner Mongolia Electric Power Research Institute
When a DC micro-grid line fails, the rapid surge of fault current is extremely detrimental to the reliability of the system power supply, so it is very important to detect and remove the fault quickly for its reliable operation. The traditional current differential protection has good quick performance and selectivity, but its sensitivity is greatly affected by short circuit impedance, and may refuse to move in case of high resistance short circuit fault. Aiming at the radial DC micro-grid, according to the current variation characteristics at both ends of the fault point, low braking coefficient is introduced to realize the detection of high resistance faults, and the protection scheme is simulated and verified by building a DC micro-grid model in PSCAD/EMTDC. The results show that the improved protection scheme can accurately identify and remove the faults when different short-circuit impedance faults occur in the protected circuit.