Fix breaking connectivity elements detection

[annetill]

Signed-off-by: Anne Tilloy [email protected]

Please check if the PR fulfills these requirements (please use '[x]' to check the checkboxes, or submit the PR and then click the checkboxes)

• The commit message follows our guidelines
• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)

Does this PR already have an issue describing the problem ? If so, link to this issue using '#XXX' and skip the rest

No.

What kind of change does this PR introduce? (Bug fix, feature, docs update, ...)

Bug fix. In main branch, we have met in a real test case, a non inverted matrix in case of a contingency that breaks connectivity. That contingency contains three elements and one of these three element is "isolated" after contingency. It means that both extremity buses belong to removed buses. I think that we are creating a loop as described in the documentation (https://www.powsybl.org/pages/documentation/simulation/sensitivity/openlf.html).

What is the current behavior? (You can also link to an open issue here)

We now have removed buses from main component. So we have to determine what is the definition of an element breaking connectivity.

What is the new behavior (if this is a feature change)?

What I understand is that a branch breaking connectivity was defined in actual release (which has no bug) by:

connectivity.getComponentNumber(lfBranch.getBus1()) != connectivity.getComponentNumber(lfBranch.getBus2())

I think we cannot have the strict equivalent with removed buses from main component but I think that the definition is that removed buses contains only one side of the branch. If both buses are in removed buses, the element is included.

Does this PR introduce a breaking change or deprecate an API? If yes, check the following:

• The Breaking Change or Deprecated label has been added
• The migration guide has been updated in the github wiki (What changes might users need to make in their application due to this PR?)

Other information:

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