Help accurately modelling lines from GRS into pypsa.

[Sol Stappard]

Hi everyone,

This is my first post here — I’m new to PyPSA and currently trying to model a real grid network. Overall it’s going well, but I’m running into some confusion when translating line data from GRS/Open Infrastructure Map into PyPSA. I’d really appreciate some advice.

One issue I’m struggling with is how to represent transmission lines that fan out into multiple parallel paths and then merge back together again. For example, I have a substation where the outgoing lines split into three, then rejoin, and sometimes fan in and out again along the route (screenshot attached).

My questions are:

• Should I just model this as a single line between buses, or would that reduce the accuracy of the model?

• If multiple circuits are represented in the GIS data, is it better to use num_parallel in PyPSA or to add separate lines?

• When lines merge along the route (but without an explicit substation), should I manually insert intermediate buses, or just treat it as one continuous line?

I’d like to recreate the grid as faithfully as possible, so any guidance on best practices for handling these kinds of line geometries in PyPSA would be really helpful.

Thanks a lot in advance!