Fault Detection and Segmentation in Medium Voltage AC Microgrid by Using Differential Protection Principle

Abstract

A microgrid is composed of a variety of energy components: distributed generators (DG), especially renewable energy and energy storage systems. Integration of DGs can significantly improve the power system's reliability, reducing the power outage duration. A distribution medium voltage (MV) system without DGs is essentially a single-point feeding source network, with overcurrent relays frequently employed to detect a fault. Overcurrent relays operate as primary and backup protection with current-graded time in a typical radial distribution network protection method. On the other hand, the protection aspect becomes one of major issues when DGs are integrated into the power system. In a microgrid, the fault current characteristic differs in isolated and grid-connected modes due to differences in power network topology, making the microgrid protection approach more difficult. The protection strategy in the microgrid should be designed to provide optimal protection to the component and the DGs based on the location of the fault occurrence, bidirectional power flow, change in voltage profile, location of DGs, type of DGs such as synchronous or inverter based DGs and uncertainty in the DGs. Therefore, this paper addresses the challenges of microgrid protection by proposing a methodology to detect and segment the fault area based on the differential protection principle. The performance of the proposed method is assessed by DIgSILENT PowerFactory simulation. The simulation results show that the differential protection-based method is able to detect and isolate the fault incident as smallest as possible.