Profiling IEC 61850

Author:Christoph Brunner, it4power, Switzerland

This raised a couple of questions: Can we avoid some of the options? What does something that is declared as optional mean? What is the consequence for the vendor that is implementing a product based on IEC 61850? What is the consequence for the end user? If we look into the details of IEC 61850, there is no generic answer to this question.

The answer would be - it depends. It depends, at which element of IEC 61850 we are looking. An optional data object in an IEC 61850 logical node results in other consequences than variations in the usage of elements of the substation configuration language (SCL). In any case, anything that is a kind of an option needs some attention by the end user and should preferably end up somehow in a project specification. This may be a time consuming process requiring a good understanding of the standard.

Where the idea of creating profiles was raised, and what is a profile of a standard? One definition I found on the web (library of congress) says: “A profile specifies the use of a particular standard, or group of standards, to support a particular application, function, community or environment. By "specifying the use" we mean to select options, subsets, and values of parameters, where these choices are left open in the standard.”

The website states further: The two primary reasons for profiles are: "to provide a specification for vendors to build to, so that the resulting products will interoperate, and to provide a specification that a customer may reference for procurement."
The idea of a profile is not new for IEC 61850. The implementation guideline IEC 61850-9-2 LE published by the UCA International UG almost 10 years ago is nothing less than a profile: It selects options and subsets and defines values of parameters for the application protection and power quality measurements.

What kind of IEC 61850 profiles do we need in the future. As already mentioned, this needs to be looked specifically - for communication services and mappings, for the engineering process and for the application modeling:

  • For the communication services, I think this should be straight forward. We may end up with 2 or 3 classes of devices - as this has already been defined by the product standard for switchgear with a digital interface according to IEC 61850 (IEC 62271-3). The classes may be applicable globally as long as we have just one mapping
  • For the engineering process, we may end up with a few options depending on the engineering approach. If a utility wants to do system integration by itself and wants to follow a top-down approach with an initial vendor independent design, the requirements on the SCL may be different than for the projects realized as turn-key approach where the user only needs to be able to modify later the design

The most interesting aspect of profiling is in application modeling. 
From the standardization community, it has been proposed to develop Basic Application Profiles. These profiles would define for a certain application (e.g. Breaker Failure Protection) the usage of the various logical nodes and data objects, the interactions between the elements of a potentially distributed function as well as the communication services used.

ENTSO-E is currently working on preparing a common profile for IEC 61850 addressing all of the aspects, but with a focus on the application modeling. They define functions, sub functions and the signals associated with these functions - both input and output. They start from their existing applications - independent from IEC 61850, and will map everything on IEC 61850 - to identify gaps in the standard and to help defining the profiles.

What is already clear is, that not all functions are similar. Many are straight forward - a protection function has well defined inputs and expected outputs. For other functions - typically everything related to scheme logic – it is less easy to define all the inputs; they may vary in number e.g. depending on the number of bays a substation has. Still, it may be possible to standardize them with some variants to be selected. But for freely configurable functions like interlocking, the whole selection of inputs depends on the concrete interlocking rule and can only be defined with a real project.

If we manage to define some good profiles for IEC 61850, this will help the acceptance of IEC 61850.  At the end, both vendors and users will benefit: the vendors will have a clear specification for their products that enables interoperability, and the users can simply refer to a particular profile that fulfills their needs.
The efforts currently taken by the ENTSO-E help to move a step forward. 

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. 

Power. Flexible. Easergy.
Let?s start with organization in protection testing