Study on Coordination of Protective Relays Between Primary Feeder and Interconnecting Transformer Grounded by SFCL of Wind Farm

In this study, we analyse the coordination of protective relays between a primary feeder and an interconnecting transformer grounded by using a superconducting fault current limiter (SFCL) of a wind farm. Most wind farms and utility systems are interconnected by a transformer. The winding configuration of most interconnecting transformers is wye grounded-delta. Therefore, the utility-side grounding of the interconnecting transformer can support a new single line-to-ground fault current path. Because the coordination plan of a protective relay in a power distribution system does not consider the new fault path, an unintended relay operation can occur. To overcome this problem, an SFCL is applied to the ground connection of the interconnecting transformer. We analyse the effect of the resistive SFCLs on the coordination of the ground faults using time-domain transient simulation software (PSCAD/EMTDC).