System Protection for vessel DC Zonal Electrical System supplied by Medium Voltage DC

The traditional radial AC distribution network in the vessel is provided with selective protection through the rational configuration of the circuit breakers based on the time-current coordination principle. However, the principle cannot be applied to the DC Zonal Electrical Distribution System (DC-ZEDS) which is a typical ring network. Furthermore, DC circuit breakers cannot take advantage of the current zero crossing, so the current-interrupted capacity of the electromechanical breakers is limited. And the wide use of DC breakers will lead to a great increase in cost, weight and size of the ship power system. Aiming at the DC-ZEDS supplied by Medium Voltage DC (MVDC), this paper has analyzed the problem of selective protection for 700V DC bus and proposed a method of protection configuration. The results obtained from the simulation model established in PSCAD/EMTDC verify the effectiveness of the method. Based on the researches, the paper makes a summary of the system protection for DC-ZEDS supplied by MVDC.