The current serialization of enumerated value inside fixed length GOOSE is limited to a 8 bit Big Endian; signed equivalent to INT8.
The conclusion of the ADHoc TF for Units in tC57WG10 Meeting in Fribourg, it was concluded that the :
. Exposing the fixed, typical, and optional units in the UML model, in the NSD and in Word document for a machine processable exposure. But first after Edition 2025.
. In 1-2 revision – Description text shall expose the units restriction; the DOName shall be unit agnostic
. Approval process for SIUnitKind similar to the abbreviation approval process. SIUnitKind extension approval done inside the TF UML and Autogeneration
The approval process is now in place in the TF UML and autogeneration.
IEC 61850-8-1 fixed length GOOSE encoding for enumeration will need to define an escape value for enumeration values bigger than the 8-bit allowed range. Tissue expected to solve the issue.
Proposal
Define an escape value for enumeration values bigger that the 8-bit allowed range.
Discussion
Created
Status
Editor Group:
The likelihood of transmitting a unit via GOOSE is very low.
Proposal: The value 127 shall be reserved to indicate "not transmitable".
Table A.2
The "Comment" cell of the type "Enumeration" shall be appended with following statement
“Any value greater than 126 shall be encoded and transmitted as 127 (not transmitable).”
Truncation only applies to fixed-length encoding GOOSE. Table 15 remains unchanged; Enumeration values greater than 126 are transmitted as such for any communication (read, write, report, GOOSE) outside fixed-length encoding GOOSE.
12 May 26
Drafting Implementation
The proposed restriction to max. 126 units is a very reasonable approach.