An Adaptive Grounding Scheme for Synchronous Based DG to Prevent the Generator Damage during Ground Faults under Different Operating Modes

Large fault currents in synchronous-based distributed generator (SBDG) can cause a serious damage to the core and windings of the generator. This paper proposes an adaptive grounding scheme to limit the ground fault currents to a safe level. To do so, a high impedance-grounding configuration is designed to operate during grid-connected mode to minimize the generator damage during ground faults. An electronic switching mechanism is provided to identify the islanded mode of operation. This switching operation strategy will modify the grounding system to low-impedance configuration during islanded-mode of operation of the SBDG to ensure the steadfast operation of the overcurrent protection (OCP) relays. In addition, the schematic diagram of the proposed grounding configuration has been presented and discussed to ensure the safe decay of the generator field current during the ground faults in the generator zone while the generator has been isolated from the grid. Simulation results validate the effectiveness of the proposed adaptive grounding scheme to ensure the fast operation of inverse OCP and to limit the fault energy dissipation level inside the SBDG to a safe level by maintaining appropriate grounding scheme during different operating modes.