Namespaces in IEC 61850

Author: Christoph Brunner, it4power, Switzerland

IEC 61850 is using the concept of Namespace in various parts. In the meantime, we are all familiar with the term Namespace, as we read it all over in IEC 61850. But do you really understand what it is? Wikipedia has an interesting explanation: “In computing, a namespace is a set of symbols that are used to organize objects of various kinds, so that these objects may be referred to by name.” Well, that sounds all right, if we understand what a set of symbols means. I think, in the context of this definition, a set of symbols may as well include a string of symbols – assuming that within a namespace the objects can be referred by a name which is a string of characters.
Now how does this fit with IEC 61850 usage of namespace? In IEC 61850 we use the term namespace mainly where we have what we call a code component. Code components are elements of the standard that are directly used as parts of software for tools and devices. I talked about code components and the process to distribute them in my column of PAC world September 2017 issue. In IEC 61850, we currently have two kind of code components: data models and XML schema files.
In both cases the term namespace is used. An example for a schema file is the schema for SCL as defined in IEC 61850-6; an example of a data model is the definition of the common data classes (CDC) as defined in IEC 61850-7-3.

In IEC 61850 we identify the namespaces themselves with a string reflecting the standard part where the namespace is defined. For the above example, that would be “IEC 61850-7-3” and “IEC 61850-6”. Besides that, namespaces for schema files have as well an XML namespace identification, which is for the SCL defined as xmlns:scl=”http://www.iec.ch/61850/2003/SCL.”

We also need to be able to differentiate between different versions of a namespace file. For that, we have three levels:

  • Version identified by a year. The version corresponds to a published Edition of the standard
  • Revision identified by a character, starting with A. The revision corresponds to the amendment of a standard Edition
  • Release identified by a number starting with 1. The release identifies intermediate distributions of namespace files during the standard development and after publication of the standard it is used to identify new releases with updates due to implemented interoperability TISSUES

As an example, the SCL schema file which corresponds to Edition 2.1 of IEC 61850-6 is identified as “IEC 61850-6:2007B4.” It has to be noted, that for a first release or a first revision, the number (1) or the character (A) can be omitted. Also, this three-level identification has only been introduced with the Edition 2.1 of the standard. So, identification of earlier namespaces may not follow exactly that scheme. As an example, the schema “IEC 61850-6:2007B” is an updated release of the Ed 2 of the part 6. At that time, we did not yet use release numbers. With today's concept, that should have been identified as “IEC 61850-6:2007A2.”
Data model namespaces are published as an XML file based on a schema defined in IEC 61850-7-7 (which is itself a namespace). The way how the data model is defined in IEC 61850 – basic types are defined in part 7-2, common data classes are defined in part 7-3 and logical nodes are defined in part 7-4 - creates dependencies between namespaces.

Different data model namespaces are introduced in part 7-1. Basic namespaces are the ones used by all others and are related to parts 7-2, 7-3 and 7-4. Domain namespaces are specific to the models of a domain like IEC 61850-7-410 for hydro power plants. Product standard namespaces typically make extensions of the nameplate, like IEC 62271-3 for switchgear. Transitional namespaces are used for technical reports and extend basic or domain namespaces. Finally, there are also private namespaces.

There are three kinds of dependencies defined:

  • Includes: this applies to domain namespaces only and means that the namespace is a superset of the one it includes; e.g. “IEC 61850-7-410” includes “IEC 61850-7-4”
  • Depends on: this applies to basic namespaces only and means that the namespace depends on the other; e.g. “IEC 61850-7-4” depends on “IEC 61850-7-3”
  • Extends: this applies to product and transitional namespaces and means that the referred namespace is extended; e.g. “IEC 61850-90-3” extends “IEC 61850-7-4”

IEC 61850-1-2, which will be published soon as a technical specification, is a guideline describing, how extensions to the IEC 61850 data model can be made and what needs to be considered. 

Biography:

Christoph Brunner is the President of his own independent consulting company it4power LLC based in Switzerland. He has over 25 years of experience with knowledge across several areas within the Utility Industry and of technologies from the Automation Industry. He has worked as a project manager at ABB Switzerland Ltd in the area of Power Technology Products in Zurich / Switzerland where he was responsible for the process close communication architecture of the automation system. He is Convener of WG 10 of the IEC TC57 and is a member of WG 17, 18 and 19 of IEC TC57. He is senior member of IEEE-PES and IEEE-SA. He is an IEEE Fellow and he is active in several working groups of the IEEE-PSRC and a member of the PSRC main committee and the subcommittee H. He is international advisor to the board of the UCA international users group. 

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