An adaptive numerical overcurrent protection scheme for microgrids

The constant proliferation of distributed generators (DGs) in power networks alters the fault current paths and shortcircuit levels. This leaves the conventional protection schemes vulnerable to impacts such as sympathetic tripping, protection blinding, miscoordination etc. Adaptive protection schemes that can vary their protection settings according to the changes in the grid environment offer comprehensive and efficient protection compared to conventional protection schemes against these protection impacts. This paper proposes a numerical protection scheme, which utilizes smart sensors, communication infrastructure and a heuristic algorithm to determine optimal adaptive protection settings. The proposed adaptive relay can determine optimal protection settings online based on the operating system mode and can continuously tune its settings to variable operating modes. This allows the relay to determine suitable protection settings according to the operating scenario for a fast and reliable operation. The effectiveness of the proposed adaptive method is demonstrated and validated on a test microgrid using a hardware-in-loop (HIL) real-time testing platform.