Interoperability Assessment Framework for IEC 61850 Multivendor Digital Substations: Challenges and Recommendations

The transition to IEC 61850-based digital substations requires robust interoperability among devices from multiple vendors. This paper presents a practical interoperability assessment framework developed and applied within an expanded multivendor laboratory environment. We address challenges including vertical and horizontal data exchange reliability, Precision Time Protocol (PTP) synchronization complexities, process interface integration using I/O boxes, and variations in vendor implementations of the IEC 61850 standard. Based on initial findings, this work details experiences gained through a twophase engineering approach (bottom-up followed by top-down), comprehensive communication chain validation, and analysis of specific vendor behaviors, such as Report Control Block limitations and PTP handling in network switches. Although conformance testing is essential, achieving interoperability alsorequires meticulous configuration, targeted testing of vendorspecific nuances, and suitable network infrastructure. Ongoing standardization efforts, particularly the collaborative initiatives of IEC Technical Committees 95, 38, and 57 through the new Joint Advisory Group JAG 25, minimize these engineering and testing demands by enabling greater inherent interoperability in IEC 61850 based substations. ... mehrWe provide recommendations for establishing similar testbeds and executing effective interoperability assessments, aiming to streamline future deployments and enhance the reliability of digital substations.