Ambiguous association cim:RatioTapChanger.TransformerEnd

[michaeldford]

There are two very similar associations in the CIM18 model between TransformerEnd and RatioTapChanger now. Traversing the path from TransformerEnd to RatioTapChanger is easily distinguishable between cim:TransformerEnd.RatioTapChanger and cim:TransformerEnd.AdditionalRatioTapChanger, but the inverses are both cim:RatioTapChanger.TransformerEnd.

This is not the only association like this in the CIM. Another example (not included in this model) is between UsagePoint and Outage, one is Energized and the other is DeEnergized, but they both have cim:UsagePoint.Outage. There are others, but I haven't made a list of them.

I'm curious to know why the multiplicity wasn't just changed to 1:0..* instead of adding this problematic association.

[AAndersn]

@michaeldford - we actually discussed this one at the in-person IEC joint TF meeting two weeks ago: https://redmine.ucaiug.org/issues/6452#note-11 and came to the same conclusion that the new association is indeed problematic. I don't think we are using it for the interop as we don't have a LTC transformers in the test model.

@tviegut - can you please re-open the redmine issue per Domagoj's note?

[AAndersn]

@michaeldford - We have removed the bad cim:TransformerEnd.AdditionalRatioTapChanger association from the UML and profiles.

The test model already used the correct assocation

<cim:TransformerTankEnd rdf:about="urn:uuid:007474bb-2033-4c84-8126-bb6d81eb5cb7">
  <gmdm:TransformerTankEnd.orderedPhases rdf:resource="http://epri.com/gmdm/2025#OrderedPhaseCodeKind.AN"/>
  <cim:TransformerTankEnd.TransformerTank rdf:resource="urn:uuid:614b908a-c376-4021-affe-2fe81d8e58c5"/>
  <cim:TransformerEnd.RatioTapChanger rdf:resource="urn:uuid:92cbb8cf-7d13-4c12-86c2-71035b1671f7"/>
...

[michaeldford]

Your system is exporting both sides of a 0..1:0..1 association, but ours only interprets one of them. We use the inverse association to place the tap changer onto the TransformerEnd: