Overview
IEC 61850-9-2:2011 (with Amendment 1, 2020) defines the Specific Communication Service Mapping (SCSM) for the transmission of sampled values over ISO/IEC 8802-3 (Ethernet). It maps the abstract sampled-value model from IEC 61850-7-2 onto a mixed protocol stack that uses direct access to the Ethernet link for high-rate sample streams, combined with selected IEC 61850-8-1 services (MMS) for control and configuration. The edition update adds synchronization references, link redundancy options and clarifications for backward/forward compatibility.
Key topics and requirements
- Sampled values mapping: Defines how the IEC 61850-7-2 sampled-value model (SV) is encoded and carried on Ethernet frames for process-bus implementations.
- Mixed stack approach: Uses direct ISO/IEC 8802-3 link access for SV streams while referencing IEC 61850-8-1 for access to SV control blocks and configuration where required.
- Control blocks evolution: Updates to MSVCB (multicast sampled value control block) and deprecation/changes regarding USVCB (unicast sampled value control block) in the amendment.
- Link redundancy: Adds an optional link redundancy layer (e.g., PRP/HSR style topologies) to improve availability of sampled-value streams.
- Encoding and presentation: Evolutions to the encoding of the sampled value buffer and ASN.1/BER presentation rules are described (Annex A includes frame format and BER guidance).
- Synchronization: Clause added in the amendment referencing IEC 61588 (PTP) and IEC/IEEE 61850-9-3 for SV synchronization requirements.
- Conformance and SCL: Requirements for conformance statements and Substation Configuration Language (SCL) elements for SV are included to enable interoperability.
- Compatibility guidance: Annex C discusses backward/forward compatibility issues between revisions.
Practical applications - who uses this standard
- Utility engineers and substation designers implementing a digital process bus to replace hard-wired CT/VT outputs.
- Manufacturers of merging units, digital sensors, protection relays, bay controllers and meters needing interoperability for sampled-value streams.
- System integrators and test labs performing interoperability testing and conformance verification for IEC 61850-based substations.
- Network architects planning redundant Ethernet topologies and time-synchronization strategies for protection and measurement applications.
Related standards
IEC 61850-9-2 is essential for anyone designing, implementing or certifying high-speed sampled-value communications on Ethernet for modern digital substations and process-bus architectures.