Adaptive protection scheme for medium voltage systems with distributed generation and islanding detection

Penetration of DGs into an existing power network have many impacts on the system, with the power system protection being one of the major issues. In this context, this paper proposes a novel adaptive protection scheme able to overcome all protection problems such as loss of coordination, bi-directionality, and islanding detection regardless of the type, number, location, and size of the connected DGs. The proposed method uses adaptive and communication relays located at both sides of each line to achieve complete isolation of the faulted line. The communication media used between relays is fiber optics. The main processor receives signals from all relays to determine the connection status of the system and sends flags refer to the Current-Time Characteristics (CCT) to each relay. Offline load-flow analysis and short circuit calculation are required to determine both value and direction of the current in each relay for each connection case, the results of load flow are used to determine the settings of each relay. ETAP program is used to simulate the tested system, and to perform the required analysis.