Power Utility Automation and Modeling - IEC 61850 Standard

The IEC 61850 standard defines a comprehensive framework for communication networks and systems used in power utility automation. It provides standardized methods for information modelling, communication services structuring and interoperability between devices used in electrical power systems.

Originally developed for substation automation systems, IEC 61850 has progressively expanded to support a wide range of applications across the power grid, including distributed energy resources, condition monitoring, renewable generation and smart grid infrastructures.

The objective of the standard is to enable devices from different vendors to exchange information in a consistent and interoperable manner by using standardized information models, communication services and engineering processes.

A key characteristic of IEC 61850 is its focus on object-oriented information modelling. Rather than defining only communication protocols, the standard defines a structured representation of power system functions using standardized information models.

These models are built using several fundamental concepts including Logical Nodes, Data Objects and Data Attributes. Logical Nodes represent functional entities such as protection functions, control functions or measurement functions within a power system.

Logical Nodes can be combined to represent complex operational behaviours within electrical infrastructures. This modelling approach enables consistent representation of power system functions across different implementations and vendors, thereby enhancing interoperability and system integration.

IEC 61850 defines several communication services that enable the exchange of data between devices and systems involved in power system automation.

The most widely used services are GOOSE messaging (Generic Object-Oriented Substation Event) which is used for fast event-based communication, Sampled Values, which are used for transmitting digitized measurement signals such as current and voltage samples, and MMS Reports which are used for client-server based communication of monitored data, alarms and status information.

These communication services are designed to meet the different performance, reliability and functional requirements of protection, control, monitoring and automation applications in electrical substations.

Beyond communication protocols, IEC 61850 introduces a complete framework for system engineering. This framework covers the modeling of system functions, the definition of device configurations and the description of information exchanges within a structured engineering process.

A central element of this engineering framework is the Substation Configuration Language (SCL). SCL is an XML-based language used to describe the specification, capabilities and configuration of an IEC 61850-based system, including intelligent electronic devices (IEDs), communication networks and functional relationships.

SCL files allow engineering tools to exchange system specification and configuration data in a standardized format, thereby enabling consistent engineering workflows and ensuring interporability across different vendors and engineering environments.

In the context of IEC 61850, top down engineering is a structured system engineering approach that starts with the definition of global system requirements and application functions and progressively refines them down to the configuration of individual devices.

Top-down engineering begins with a system level functional specification, independent of any specific vendor or IED, and focuses on what functions are required and how they interact, rather than how they are implemented. These functions are modelled using standardized IEC 61850 information models and are later allocated to physical devices during the detailed design phase.

Basic Application Profiles (BAPs) play a key role in supporting this top down approach by providing functional templates that define the required Logical Nodes, information exchanges, and communication services for a given application. By clearly specifying functional boundaries and expected interactions at an early stage, BAPs enable consistent system design, improve interoperability, and reduce ambiguities when mapping system level requirements to device level configurations.

As a result, BAPs help bridge the gap between functional specification and implementation, making top down engineering more efficient, repeatable, and multi vendor compatible.

IEC TR 61850-7-6 provides guidelines for defining Basic Application Profiles (BAPs) by describing the functional behaviour of protection, automation and control applications, their IEC 61850 information modeling, and the associated information exchanges.

Earlier editions of the report focused primarily on textual documentation of application functions. The latest edition introduces support for describing Basic Application Profiles in machine-processable SCL format, through the introduction of a new file type: the ASD (Application Specification Description) file. An ASD formally describes an application at the functional level, including the involved Logical Nodes, required data exchanges, and communication services, independently of any specific system or device.

In a top‑down engineering workflow, ASD files represent the starting point of system engineering. They provide standardized, reusable functional building blocks that can be selected and combined to define the overall system behaviour. These application specifications are then instantiated at the system level in an SSD (System Specification Description) file, as defined in IEC 61850‑6. The SSD describes the system architecture – including Bays, Voltage Levels, Functions, Logical Nodes, and optionally specified devices (IEDs) - while remaining independent of specific IED implementations.

This evolution enables engineering tools to process application specifications directly, thereby facilitating the automation of system design, consistency checks and interoperability validation.

The methodology defined in IEC TR 61850-7-6 builds upon several other documents within the IEC 61850 series, in particular IEC TR 61850-90-30 and IEC 61850-6.

Together these documents provide a coherent framework for describing application functions and their associated communication mechanisms.

Further information about the IEC 61850 standard and the definition of Basic Application Profiles can be found in the official IEC standards and technical reports.

A detailed description of MODSARUS and its relationship with Basic Application Profiles is available in the product description provided with the MODSARUS software.