Localized Fault Protection in the DC Microgrids with Ring Configuration

DC Microgrids with ring configuration promises a new opportunity for distribution systems, but it is still faced with critical protection problems. In this paper, a localized protection method based on the transient behavior of fault current is presented, which can locate the fault and calculate the fault resistance by only local measurements. Besides, due to the calculating the fault resistance in the proposed scheme, the High Impedance Fault (HIF) is locatable by this method. Another important feature of this method is the reduction of the number of relays. The proposed method is localized and only needs two Protection Detection (PD). This feature of the proposed method removes the communication link, noise, and reduce the cost of the system. Due to the bidirectional current flow in ring systems, the proposed protection scheme considers that and locates fault from two different sides. The mathematical equations for calculation of fault location and resistance by using local measured values are derived. The fault location is tested on a multi-source ring-type DC Microgrid in Digsilent, and results show the effectiveness of the proposed method in different fault locations and resistances.