This is the second part of a two-part paper series. In the Part 1 paper, the authors summarize the utility workshop outcomes and low-voltage network modeling approaches. In this Part 2 paper, we developed and validated an accurate network protector relay model and interfaced a commonly used network protector relay hardware with our real-time simulation system. Hardware-in-the-loop protection studies are performed to assess the impact of distributed energy resources and benchmark a mitigation strategy. Simulation results suggest that the network protector reverse trip and auto-reclose functions are negatively impacted by the high distributed energy resource penetration. To accommodate DER backfeed while remaining secure and reliable for faults on primary feeders, we recommend options for a rate-of-change-based blocking scheme and a protection setting change. Finally, future mitigation ideas and standard revisions are discussed.

The growing distributed energy resources (DER) penetration in the low-voltage network (600V and below) challenges the existing protection philosophy and practice. To assess the impact of high DER penetration, the authors built a representative low-voltage network model in real-time electromagnetic transient software and performed hardware-in-the-loop (HIL) protection studies. In the first stage of the effort, the authors invited four major U.S. utilities with low-voltage networks to a technical workshop to survey the modeling and study needs. Guided by the workshop discussions, the authors developed various real-time simulation models, including a low-voltage network model, a model of a commonly used network protector relay, and DER models. Finally, the authors conducted hardware-in-the-loop protection studies to investigate and mitigate the high DER penetration impacts. Part 1 of the paper summarizes the technical workshop outcomes and low-voltage network modeling approaches. Part 2 of the paper reports the HIL simulation setup, high DER penetration impact assessment, and benchmark results of a promising mitigation solution.

Fault responses of inverter-based resources (IBR) are primarily dictated by the control algorithms and are fundamentally different from conventional synchronous generators. Hardware-in-the-loop simulation, commonly viewed as a robust tool for protection setting prototyping and testing, is used in this paper to investigate the impact of a wind farm, with type-4 full converter wind turbines, on the protection of a 345 kV transmission line in Texas, United States. This paper discusses two critical topics in detail: (1) wind farm IBR model development and validation against vendor PSCAD model, and (2) IBR impacts on distance and current differential protection.