by Keith Gray, POWER Engineers – a member of WSP, USA
OCL-based validation represents a fundamental improvement in how IEC 61850 systems are engineered.
Poor SCL file quality remains one of the most common causes of IEC 61850 engineering and interoperability issues. As the industry increasingly relies on top-down engineering, multivendor system integration, and automated engineering and testing tools, the quality of the underlying SCL files becomes critical. Recognizing the impact that SCL quality has on interoperability, the 2026 UCA International Users Group (UCAIug) IEC 61850 Interoperability Testing event designated SCL quality as a major focus area. This article describes the automated validation process being used for the 2026 IOP, explains how it is improving SCL quality, and discusses the lessons being learned for both IEC 61850 standards development and engineering tool implementation.
If you have performed IEC 61850 multivendor engineering, you have probably seen issues with SCL file quality. These issues often appear when transferring an SCL file between engineering tools, but they can also affect testing and other parts of an IEC 61850 system’s lifecycle. The receiving tool reports one or more errors and refuses to import the file. You are either stuck waiting for the vendors to figure out the incompatibility and then fix it, or you have enough knowledge to dig into the XML, find and fix the issue yourself. Similar SCL quality issues were frequently encountered during the previous two IOPs, where they often resulted in additional engineering effort to identify and correct interoperability problems.
Recent WG10 efforts to improve the quality and consistency of IEC 61850 engineering artifacts made it possible to significantly enhance SCL validation for the 2026 IOP. The publication of IEC 61850-6-3 between the 2024 and 2026 IOPs is one example of these improvements. In addition to XML schema and NSD validation, the availability of standardized OCL rules and enhancements to RiseClipse, the open-source SCL validation tool, enabled a more comprehensive validation process. As a result, the IOP team introduced an automated quality gate implemented through a continuous integration pipeline.
The validation process consists of three complementary layers that together verify the structural, modeling, and semantic quality of an SCL file. XML Schema (XSD) validation verifies that the file is structurally correct. Namespace Definition (NSD) validation verifies the correct use of IEC 61850 data models. Object Constraint Language (OCL) validation verifies semantic rules and relationships that cannot be expressed through schema validation alone.
The automated validation workflow begins when one or more SCL files are submitted or updated. XML schema validation is performed first because the subsequent validation steps assume the SCL file is structurally correct. Once XML schema validation is completed, the files are then validated against the Namespace Definition (NSD) files and the OCL rule set. If there are errors in any of these pipeline steps, reports are automatically generated for both the submitter and the IOP problem report process. The identified issues are corrected and the files are resubmitted. Once all validation checks pass, the files are accepted for use in the IOP engineering process.
Early use of the validation process has already demonstrated its value. Applying the validation steps to real-world SCL files has identified issues not only in the submitted files, but also in the validation rules themselves. One OCL rule was found to contain an error and has been corrected for use during the IOP. This correction will be submitted to the IEC 61850-6-3 Task Force for inclusion in the official rule release. Another OCL rule was found to cause problems for “pure client” ICD files and was temporarily removed from the validation process while the IEC 61850-6-3 Task Force develops a correction. Vendors are also being notified of issues in their SCL files, which they are correcting prior to those files being included in the IOP engineering process.
Early results show that automated validation is improving the quality of submitted SCL files while also helping identify needed improvements in validation rules and tooling. The experience gained during the 2026 IOP is expected to provide valuable feedback for future IEC 61850 engineering practices, validation technologies, and standards development efforts. As IEC 61850 engineering continues to become more automated and specification-driven, processes such as this will play an increasingly important role in achieving reliable multivendor interoperability.
Biography:
Keith Gray (P.E.) received his M.S. in Electrical Engineering from Southern Illinois University Edwardsville in 2005. He is a protection, automation, and control engineer with over two decades of experience working for POWER Engineers, a member of WSP. He has focused on digital substations and IEC 61850 since 2014 and is the co-convener of IEC TC57 WG10. He is currently participating in multiple CIGRÉ working groups covering various IEC 61850 topics and he is active in the UCA International Users Group IEC 61850 interoperability events. He is a licensed Professional Engineer in the state of Idaho.
