Executive Summary : | The traditional overcurrent protection mechanism in distribution systems has been ineffective due to the inclusion ofDGs, which can cause a wide range of fault current levels, insufficient fault current levels for islanding conditions, uneven fault patterns, reduced relay reach, and different fault types in different operating modes. This proposal aims to address these issues by designing feeder relays with settings that consider these situations while planning a protection strategy. The proposed work will determine relay settings considering not only maintaining coordination between relays but also detecting faults irrespective of uneven fault patterns, level of fault current, types of faults, grid-connected and islanding operating modes, and changing connections of DGs. A single protection module will be used for all types of fault situations, and the relays settings will be designed to minimize dependency on frequent communication and detection of the operating mode/topology. A composite fault severity-based actuating factor (CFSAF) will be developed for relays, detecting faults regardless of fault types and levels. A non-fault discriminating factor (NFDF) will be incorporated into the relaying to achieve better selectivity and avoid sending trip signals under non-faulty conditions. The relay settings will be determined to preserve coordination between relays considering variable situations. The performance of the proposed methodology will be investigated on real-time simulators based testbeds, considering detailed modeling of system components and different case studies including different types of faults, operating modes, connections, sizes of DGs, and non-fault conditions. The methodology will help design a self-sufficient protection strategy for an AC microgrid, ensuring successful detection of fault currents and clearance on time while preserving coordination between relays in variable active distribution networks. |