IEC 61850 – Data model

IEC 61850 is a new standard for communication in substation automation systems. It enables the integration of various functions such as protection, control, measurement and monitoring in a substation, and supports distributed applications, interoperability and complex operations.
This standard consists of 10 main parts and is very comprehensive. To make it easier for readers to find relevant information, this article will introduce the data model in the IEC 61850 protocol.
The data model is a high-level model that defines the structure and organization of data for a device.

Data model

The IEC61850 protocol defines a hierarchical structure of data and functions for substation automation. The main components of this structure are:

Physical Device (PD): A PD is a smart electronic device, such as an IED, RTU, relay, meter, etc., that is connected to the communication network system in the substation. A PD can contain one or more Logical Devices (LDs) that represent different functions or devices within the PD.

Logical Device (LD): An LD is a logical grouping of data and functions that corresponds to a physical device or part of it. For example, an LD can represent a circuit breaker, a disconnect switch, an earth switch, a transformer, etc. An LD can contain multiple Logical Nodes (LNs) that describe the data and functions of the LD.

Logical Node (LN): An LN is a basic building block of data and functions in the IEC61850 protocol. An LN contains one or more Data Objects (DOs) that define the information related to the LN. There are 86 predefined types of LNs in the protocol, divided into 13 groups according to their functionality: protection, switchgear, measurement, fault recording, etc.

Data Object (DO): A DO is a data class that specifies the detailed information about a device or function defined in an LN. For example, a DO can represent the status, command, setting, measurement, or event of a device or function. A DO can contain one or more Data Attributes (DAs) that define the properties of the DO.

Data Attribute (DA): A DA is a data element that describes a specific property of a DO. For example, a DA can represent the value, timestamp, quality, or description of a DO. A DA can have different data types, such as boolean, integer, float, string, etc.

For example:
Device Relay1 is a Logical Device (LD) containing 2 Logical Nodes (LN): MMXU1 and XCBR2.
On Relay1 device:

XCBR2 is a Logical Nodes (LN) that defines circuit breaker control functions, containing Data Objects (DO) including:
IEDs: Relay1/XCSR2.ST.Pos: CB position status.
IED: Relay1/XCSR2.CO.Pos: circuit breaker control command.

MMXU1 is a Logical Nodes (LN) that defines the measurement function of the Relay containing Data Objects (DO) including:
IEDs: Relay1/MMXU1.MX.A.PhA: is the phase A current value
IEDs: Relay1/MMXU1.MX.PhV: is the phase voltage value

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