Common Information Model (CIM)

CIM defines a canonical data model that represents every physical asset and logical function in a power system as a standardized object with defined attributes and relationships.

• Classes represent real-world entities like Breaker, ACLineSegment, and SynchronousMachine
• Attributes define properties such as ratedCurrent or normalOpen state
• Associations map how objects connect, e.g., a Breaker is contained within a Bay

This eliminates semantic ambiguity where one system's 'disconnector' is another's 'isolator.'

CIM is formally codified in two complementary IEC standards that address different utility domains.

• IEC 61970 (Energy Management): Focuses on the transmission network model, topology processing, and real-time SCADA data exchange for control centers
• IEC 61968 (Distribution Management): Extends the model for distribution assets, customer metering, work management, and asset tracking

Both standards share a common Unified Modeling Language (UML) base, ensuring consistency across the enterprise.

CIM defines standardized XML and JSON message formats for specific business processes, enabling plug-and-play integration between vendor systems.

• CIM/XML for Network Model Exchange: Used to export a complete power system model from one application and import it into another without manual mapping
• IEC 61968-9 for Meter Reading: Defines payloads for exchanging interval meter data between a meter data management system and a billing engine
• IEC 61968-4 for Asset Management: Standardizes work order and asset lifecycle messages

Each message profile is a strict subset of the full CIM, constrained for a specific use case.

CIM leverages class inheritance to model the power system with increasing specificity, reducing data duplication and enforcing logical consistency.

• PowerSystemResource is the abstract root class for all grid assets
• Equipment inherits from it, adding terminal and connectivity attributes
• Switch inherits from Equipment, adding normalOpen and ratedCurrent
• Breaker inherits from Switch, adding breakingCapacity and arc-quenching properties

This hierarchy allows applications to query all Switch objects generically or target Breaker objects specifically.

CIM represents the electrical network as a node-breaker graph, capturing the detailed internal busbar configuration of substations.

• ConnectivityNodes are zero-impedance points where Terminals of ConductingEquipment meet
• TopologicalNodes are formed by merging ConnectivityNodes through closed switches, representing the energized bus
• This dual representation allows both detailed switching analysis and simplified power flow calculations from the same model

Accurate topology is essential for state estimation, contingency analysis, and Volt-VAR optimization.

Full CIM adoption is impractical for any single interface. Instead, utilities define application profiles—constrained subsets of the model tailored to a specific business context.

• A profile restricts which classes, attributes, and associations are required or optional for a given message exchange
• Profiles are documented in machine-readable form, allowing automated validation of XML payloads against the profile schema
• This ensures that a DMS exporting a network model includes only the data a planning tool actually needs, reducing complexity and bandwidth

Profile governance is managed by the CIM Users Group (CIMug) to ensure cross-vendor consistency.