Protection issues and solutions for protecting feeder with distributed generation

These days the distributed generation (DG) is developing fast because of the benefits it could bring into the system, such as the relief of transmission and distribution burden and usage of the clean energy. However, at the same time, DGs are also bringing some challenges to well-known traditional protections in distribution systems, especially with high penetration level of DGs. One of them is during a fault where DG could contribute to the fault current in addition to the contribution from the existing power grid. This paper will first give an overview of the distributed generators behavior and their current contribution during the fault. Special focus will be given to inverter interfaced DG (IIDG) which has fault behavior significantly different from that of a conventional DG while having not been adequately studied. It will examine the key features of IIDGs´ fault behavior with respect to interference with distribution protection. As an example, current and voltage waveforms from a commercially available photovoltaic converter will be shown through a hardware-in-the-loop (HIL) simulation setup using real-time digital simulator (RTDS). Then impact and complications of such fault behavior of DG on the traditional feeder overcurrent protection performance will be analyzed as well. Finally, possible application solutions are presented and analyzed for the feeder protection with a considerable penetration of DGs. This includes usage of directional comparison and distance protection and partial differential protection.