LEA-based Hardware in the Loop Validation for DER Integration Impact on Distribution Protection

The transition from big conventional bulk generation to small dispersed renewable electricity production coupled at medium and lower voltage levels resulted in bi-directional power flow and an active distribution network, which was previously considered to be a passive network. This paradigm shift brings many challenges for protection performances and coordination. As a result, this paper first investigates the impacts of Distributed Energy Resource (DER) integration on distribution protection and then applies the hardware SEL 451 relay for validation. Two of the most common protection failures with DER integration, namely, reverse power flow and sympathetic tripping cases, are examined for a microgrid in this study. Firstly, the system is modeled in PowerFactory for short circuit calculation and protection coordination study. With the help of PowerFactory simulation, coordinated relay settings are subsequently extracted for validation in hardware in the loop testing with SEL 451 relay in real-time digital simulation (RTDS). Both simulation case studies and hardware tests have shown that the DER contribution in healthy conditions as well as during the fault can result in maloperation of the relay. Different from the traditional power amplifier-based testing, the hardware in the loop testing in this work uses Low Energy Analog (LEA) signals output from the GTAO card of RTDS feed directly to SEL 451 relay. Two different feedback methods with Digital Input (DI) and IEC GOOSE signal are tested to compare the time of operation in each case.