Unified IED modelling using IEC 61850 Flexible Product Naming

Michael Haecker and Christoph Bennauer, Schneider Electric, Germany

Interoperability versus Interchangeability
Interoperability is the ability of two or more intelligent electronic devices from the same or from different manufacturers, to exchange information in such a way that a correct functional co-operation between information producer and information recipient is achieved.

To achieve this goal the standard provides the following key elements:

Standardized class-oriented data modelling method to describe each possible data in its functional context which each tool and component in the system can understand and process (as long as both sides are using the same common data class)

Standardized file format for the data model description and the device capabilities between tools of different manufacturers

Standardized communication procedures called “services” to facilitate system wide interaction between components of different manufacturers to act as a complete system

Standardized mapping on a network to use unique communication and hardware layers

Test methods definition to verify an interoperable behavior of all system components during testing

Interchangeability is the possibility to replace a device supplied by one manufacturer with a device supplied by the same or another manufacturer, providing the same functionality with no impact on the rest of the system.

In terms of a communication protocol, compromises can be found to achieve an acceptable level of interchangeability without the devices providing the exact similar number and structure of data objects of their data models.

Conformance Testing
Conformance Testing was added to verify that the implementations of IEC 61850 into devices and tools of different manufacturers are conformant to this standard. Running a set of predefined test procedures, proof is given of the correct data modelling, implementation of services, provision of description files and documentation.

This testing only proves that there is no inconsistency between the data model, the description files and the documentation. The validation of which functional objects are modelled and how they are modelled is out of scope of conformance testing.

PN, FN versus fPN

As the standard offers a very flexible way of data modelling and allows a lot of room for interpretation, the data model of each IED from different manufacturers can diverge.

The freedom of defining the data model and the level of implementation allowed to manufacturers may result in an issue around interchangeability. In IEC 61850 the base data model of an IED as predefined by the manufacturer is referred-to as “Product Naming” (PN).

Product naming (PN) is the fixed or default data model of an IED reflecting the information content of the hierarchy/structure of functions inside an IED.

IEC 61850 also defines Functional Naming (FN), which is the reflection of the functional application view in the reference of information and is typically a primary equipment-oriented view.

To reach any level of interchangeability, it is required to align the data models in the IEDs to have the same naming and semantic of all data exchanged. IEDs that allow to modify and to customize parts of the whole data models, provide “Flexible Product Naming” functionality.

Flexible Product Naming (fPN) allows the data model of an IED to be modified up to a certain level to reflect the hierarchy/structure defined by the overall scheme. The user, in control of the naming details is able to arrive at installation specific, manufacturer independent IED data model conventions. The data model definitions can be applied to all IEDs supporting this facility, to modify their Product Naming into data models which are conformant and relevant to both the site and customer specific conventions. Based on this customized data model, all relevant data can be exchanged between the IED and its communication peers in an interoperable way.

Power. Flexible. Easergy.
BeijingSifang June 2016