Overview
EN 61850-9-2:2011 (IEC 61850‑9‑2:2011) specifies the Specific Communication Service Mapping (SCSM) for transmission of sampled values (SV) in power utility automation. It maps the abstract sampled‑value model from IEC 61850‑7‑2 onto an Ethernet/IP stack using direct access to an ISO/IEC 8802‑3 link (Ethernet) in combination with IEC 61850‑8‑1. The standard is focused on reliable, time‑sensitive transport of analog measurement samples (e.g., currents, voltages) within substations and other power‑system environments.
Key topics and technical requirements
- SV mapping onto ISO/IEC 8802‑3: Defines how sampled‑value Application Service Data Units (ASDUs) are carried directly over Ethernet frames for low latency transmission.
- Multicast and Unicast control blocks: Defines MSVCB (Multicast Sampled Value Control Block) and USVCB (Unicast Sampled Value Control Block) structures and services for publishing/subscribing SV streams.
- Protocol stack and profiles: Describes A‑Profile and T‑Profile usage, interactions with IEC 61850‑8‑1 (MMS) for configuration and with direct link‑layer SV transport for samples.
- Encoding and buffer update: Evolution of encoding rules for the sampled value buffer (ASN.1 / BER basics are referenced) to ensure deterministic decoding of samples.
- Link redundancy (optional): Introduces an optional link redundancy layer and references high‑availability redundancy methods (e.g., PRP/HSR) to improve availability.
- Link layer details: Redefinition of reserved link‑layer fields, VLAN ID/priority recommendations and assigned Ethertype usage for SV frames.
- Conformance & SCL: Specifies conformance testing guidelines (PICS) and integration with Substation Configuration Language (SCL) for automated configuration exchange.
Practical applications and users
Who uses EN 61850‑9‑2:
- Utility engineers specifying digital substation communications and process‑bus architecture.
- Relay, IED and merging‑unit (MU) manufacturers implementing sampled‑value transmitters/receivers.
- System integrators and OEMs deploying protection, control and monitoring systems requiring low‑latency measurement sharing.
- Test labs and certification bodies validating conformance to IEC/EN 61850 profiles.
Common applications:
- Digital substations and process bus implementations where precise, time‑synchronous sampled data are exchanged between MUs and protection/measurement IEDs.
- Telecontrol and telemetry interfaces within substation automation requiring deterministic sample delivery.
- High‑availability protection systems using redundant Ethernet topologies.
Related standards
EN 61850‑9‑2:2011 is essential for anyone designing, implementing or testing Ethernet‑based sampled‑value transport in modern substation automation systems.
