Protection of Renewable-dominated Microgrids: Challenges and Potential Solutions

Abstract

In this report we address the challenge of designing efficient protection system for inverterdominated microgrids. These microgrids are characterised with limited fault current capacity as a result of current-limiting protection functions of inverters. Typically, inverters limit their fault contribution in sub-cycle time frame to as low as 1.1 per unit. As a result, overcurrent protection could fail completely to detect faults in inverter-dominated microgrids. As part of this project a detailed literature survey of existing and proposed microgrid protection schemes were conducted. The survey concluded that there is a gap in the available microgrid protection methods. The only credible protection solution available in literature for lowfault inverter-dominated microgrids is the differential protection scheme which represents a robust transmission-grade protection solution but at a very high cost. Two non-overcurrent protection schemes were investigated as part of this project; impedance-based protection and

Protection of Distributed Generation: Challenges and Solutions

“…Different pilot protection logics can be used to find out the location of the fault. For instance, a pilot protection logic based on permissive and blocking signals could be realized as follows [77]: 1) Any relay that detects a fault will: • Sends a block signal to its reverse zone breakers.…”