Digital Twin in Relay Protection for Converter-Based Networks: From Foundational Vision to Closed Loop Co-Simulation and Lifecycle Integration

(BESS), and HVDC interconnections. This shift introduces fault and transient behaviors that differ from conventional synchronous machine–dominated networks: fault currents are often magnitude-limited, short-lived, and shaped by control functions such as fault-ride-through, with phase relationships that can deviate from traditional assumptions. These characteristics challenge established protection principles and can compromise dependable and secure operation of conventional functions.

Reliable performance in inverter-dominated networks increasingly requires extensive testing across a wide range of fault scenarios, yet validation on physical devices is costly, timeconsuming, and operationally risky. Digital twin technology addresses these issues by enabling relay logic, settings, and IEC 61850-based communication schemes to be executed and tested in a fully virtual environment, supporting efficient iterations and renewable-specific fault scenario coverage.

This paper reviews the evolution of digital twins for relay protection, from early relay twins for virtual logic execution to open-loop interaction with digital test set twins, culminating in a closed-loop co-simulation architecture. The proposed approach enables dynamic relay–test set interaction, automated performance evaluation, and validation of complex schemes with high channel counts. Applications across the protection lifecycle, implementation challenges, and needs for future standardization are discussed, with reference to ongoing industry efforts towards interoperable protection digital twins..