IEC 61970 / 61968 — CIM
The Common Information Model — a UML-based semantic model of a power system that lets EMS, ADMS, and market systems exchange network topology, equipment, and operational state in a vendor-neutral way. The model that lets a new ADMS know what is in the substation it is being asked to operate.
Also: CIM, 61970, 61968, Common Information Model, CIM/XML, CIM RDF
The Common Information Model (CIM) is a UML-based semantic model of a power system. It defines what an “AC line segment” or a “transformer winding” or a “topological node” is, in a vendor-neutral way, so that two systems written by different vendors can exchange power-system data without first agreeing a custom schema.
CIM is split across IEC working groups:
- IEC 61970 — transmission and EMS context (TC 57 WG 13).
- IEC 61968 — distribution and ADMS context (TC 57 WG 14).
- IEC 62325 — energy market context (TC 57 WG 16).
The three work together: 61970 defines the base model, 61968 extends it for distribution, 62325 layers market structures on top. They are collectively referred to as “CIM” by everyone who isn’t on the working groups.
Why the model matters
A modern utility runs separate vendor systems for SCADA, EMS, ADMS, planning, GIS, asset management, outage management, and market operations. Each historically had its own data model. Keeping those models in sync was an integration nightmare measured in dozens of bespoke ETL pipelines.
CIM exists so that the network topology — substations, lines, transformers, switches, generators, loads — can be modelled once, in CIM, and exported to any consumer in a standard format (typically RDF/XML per IEC 61970-552). When something physical changes in the network, the CIM model changes once and propagates.
What it actually contains
The 61970-301 base classes cover, in rough groupings:
- Topology — connectivity nodes, terminals, the graph structure of the network.
- Equipment — switches, breakers, transformers, lines, capacitors, loads.
- Measurements — analog and discrete measurements with references to the equipment they measure.
- Generation — generating units and their dispatch parameters.
- Wires — line segments, ratings, impedances.
- State variables — the operational state to feed to a state estimator.
61968 adds distribution-flavoured classes — fuses, customers, meters, asset records. 62325 adds market-flavoured classes — bids, offers, settlement metering, balancing positions.
CGMES — the European profile
ENTSO-E (the European association of transmission operators) published the Common Grid Model Exchange Standard (CGMES) as a profile of CIM specifically for inter-TSO model exchange. It defines exactly which CIM classes and attributes are required for which operational use cases — equipment model, topology, steady-state hypothesis, dynamic data — and is the format in which European TSOs exchange grid models for day-ahead congestion forecasting and inter-area coordination.
In GB, the National Energy System Operator (NESO) uses CGMES to exchange grid models with neighbouring European TSOs and with the GB transmission and distribution operators. CGMES is therefore the substrate for inter-operator network models, even though within each operator’s own EMS the model is held in vendor-specific stores.
Where CIM and IEC 61850 meet
CIM and 61850 are sometimes confused because both come from IEC TC 57 and both model power systems. They sit at different scales for different audiences:
| CIM (61970/61968) | IEC 61850 | |
|---|---|---|
| Scope | Wide-area network model | Substation device model |
| Detail level | Equipment-and-topology | Logical-node-and-data-object |
| Use case | EMS / ADMS / market integration | IED configuration and substation engineering |
| Exchange format | CIM RDF/XML | SCL |
| Time scale | Network state at minutes-to-hours granularity | Per-frame at microsecond granularity |
Bridges exist — IEC 61850-90-30 specifies harmonisation between CIM and 61850 — but in practice the two remain distinct working ecosystems with different tools and different engineering communities.
Why the substation architect cares
For a substation modernisation programme, CIM is the model the target ADMS or EMS will need to consume to know what the upgraded substation contains. A 61850-engineered substation has an SCL file describing its IEDs and their data points; that SCL file has to be ingested into the operator’s CIM-based network model so that the new substation appears in the operator’s overall view of the grid.
The integration question that shows up in every modernisation programme is: who owns the SCL → CIM transformation, who validates it, and how does it stay in sync as the substation evolves over time? The answer is rarely simple and is one of the larger soft costs of any 61850 deployment.