Adaptive Protection Scheme for Medium Voltage Systems with Distributed Generation and Islanding Detection

Abstract

Utilization of Distributed Generators (DGs) reduce the demand in both distribution and medium-voltage networks, without any need for transmission system expansion. 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 protection problems associated with connection of DGs. The proposed protection scheme addresses the 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. The used communication media is fiber optics. 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 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. ETAP program is used to simulate the tested system, and to perform the required analysis.