Integrating distance relay blinding constraints into security-constrained economic dispatch via protection shift factors

The rapid integration of Inverter-Based Resources (IBRs) is introducing new couplings between market-based dispatch and distance-relay security. In meshed transmission networks, economy-driven dispatch of low-cost IBRs can increase reverse fault-current infeeds and erode Zone 1 security margins. This paper proposes a new preventive dispatch framework that integrates specific distance-relay blinding margins into linear Security-Constrained Economic Dispatch (SCED) constraints through a developed Protection Shift Factor (PSF). The proposed method separates a post-fault network-side transfer factor from an IBR-level fault-current sensitivity using a source-resolved current tracing methodology. This separation reveals whether higher IBR dispatch increases the relay-relevant fault current. Results from Electromagnetic Transient (EMT) simulations of the IEEE 14-bus network using a generic Western Electricity Coordinating Council (WECC)-type IBR control policy show the IBR’s fault-current contribution decreases as its pre-fault power dispatch increases. Conversely, under a retained-active-current policy, the IBR’s fault-current contribution increases with higher pre-fault dispatch, thereby establishing an operationally meaningful protection constraint for SCED. The study also demonstrates realistic distance-relay underreach scenarios considering a nearby dispatch-boundary case used for SCED. In the SCED example, conventional dispatch exceeds the EMT-identified projected-current limit, while the protection-constrained dispatch curtails the network-sensitive low-cost IBR and produces a protection-induced nodal-price deduction. Furthermore, the scalability of the framework is validated on the WECC 240-bus system, demonstrating that the linear surrogate maintains exceptional accuracy across bulk grids and successfully arbitrates numerous interacting distance-relay constraints. The developed framework provides a practical route for carrying EMT-identified relay-security margins into linear market clearing and helps mitigate pricing protection-security congestion.