Evaluation of fault contribution in the presence of PV grid-connected systems

An increasing number of distributed generations (DGs) being connected to the utility grid has raised the need for new and more rigorous standards for power quality, safety operation and islanding protection of the grid interconnection. This paper focuses on the fault contribution of a distributed generation, specifically PV grid-connected system in the event of an unintentional islanding. An experimental setup is created using an off-the-shelf grid-connected inverter to emulate the event of a fault occurred on a distribution feeder. An extreme case scenario, according to the IEEE standard, that will result in the highest fault contribution of the PV grid-connected system is considered for conservative results. The experimental results have shown that, without violating the specified criteria in the standard, the grid-connected inverter takes times to detect an islanding condition and stop energizing. The experimental results are used to investigate the fault contribution in a distribution system. This study has shown that higher penetration level of the PV grid-connected systems results in higher fault current which unavoidably has effects on the protective devices. This observation introduces the possibility of selecting and/or upgrading protective devices in a distribution system.