818   Instance numbers in 7-1 and 7-2

Created: 06 Feb 2012

Status: Not Applicable

Part: Part 7-1 (2011; Edition 2)



Clause: 14.6


Category: Issue for edition 3 of this part


IEC 61850-7-2 Edition 2 clause "22.2 Referencing an instance of a class" defines:

"DataObjectClassName = 12 characters (as, for example, used in IEC 61850-7-4); start with upper case alpha character; one numeric last character indicates multiple instantiation capability"

It just defines: "one numeric last char" ... any!?

IEC 61850-7-1 Edition 2 clause 14.6 "Specialisation of data by use of number extensions"


"Standardised data names in logical nodes provide a unique identification. If the same data (i.e. data with the same semantics) are needed several times as defined, additional data with number extensions shall be used.
The rules for number extensions shall follow the naming conventions defined in IEC 61850-7-2 and be as follows:

– the number extension usage shall only be defined by the owner of the data namespace. This shall be done by adding the number extension 1 to a data object name (e.g. data1),

– data with no number extension shall not be extended by third parties,

– data with the number extension 1 can be extended. Number extensions may be ordered or not (1,2,3,4, or, 1,2,19,25),

– if only one instance of an extendable data is present in an LN, it shall have the number extension “1”."

The two documents IEC 61850-7-2 Ed2 (one (any!) numeric char) and IEC 61850-7-1 Ed (numeric char 1) are not 100 percent consistent.

What does the last bullet in the excerpt of 7-1 mean? "if only one instance of an extendable data is present in an LN, it shall have the number extension “1”."

Does it mean instantiable? Or a EX DO?


Define the "last char" in 7-2 as "1" or change in 7-1 to "one numeric last character"

Discussion Created Status
23 Mar 12 Not Applicable
27 Feb 12 Discussion (red)
There is a difference of meaning in 7-2 and 7-1. 7-2 describes mainly the general syntax of instances, while 7-1 describes how the classes are defined and what this means. This part will anyhow change with the UML model description of the classes and introduction of a new presence condition (multiply instantiable), therefore neither a change to 7-2 nor to 7-1 is needed at the moment, both have to be adapted to the UML model conventions with Ed. 3. 14 Feb 12 Discussion (red)


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