Description
Further investigations following #179 raised awareness about some conceptual drawbacks of current PowerSystemDataModel design and implementation. Highly detailed models with bus bar systems and switch gear raise some modelling needs, that are not covered, yet. A condensing figure of those issues can be seen in the following and will be further detailed.
Issue 1
In actual operation and design of grids in higher voltage levels, transformers do have switch gear up- and downstream of them. They allow not only for opening circuits, but also die switch between different bus bars, as well at the high and the low voltage side.
If we would like to allow users to perform switching operations after establishing the models, this is challenging the definition, of what a sub grid is. Depending on the switch gear state of the left and right hand side, the lower part of the figure can form one or two galvanically separated sub grids (when switch at 4 is closed). So: What actually defines the boundaries of a sub grid? It should be the goal to prevent partial models (lines, transformers, ...) to move from one to another sub grid model when performing switching operations. How can the topological relation between upstream and downstream sub grids be modeled flawlessly?
Additionally, conceptual constructs like substations, feeders, switch gear fields etc. are not covered explicitly, yet.
Issue 2
During operating switch gear at lines, those operations can change topology as well. Feeders may move form one galvanically separated grid to another, may couple previously decoupled grids etc. This also has implications tho sub grid definition.
Issue 3
Has to be seen similarly. Switch gear that is there for explicit coupling of bus bars, can also change topology.
However, additionally to covering topological concept by models, it would also imply the need to further enhance and adapt logical validation of models. As there is no pressuring need to have those features, yet, we only raise awareness of those drawbacks now and postpone addressing them to a later stage.