TAMU Transformer pu conversion

[trevorb1]

Version Checks (indicate both or one)

• This bug exists on the master branch of PyPSA-USA.

• This bug exists on the develop branch of PyPSA-USA.

The Issue

The TAMU network groups lines and transformers together in the branches.csv file. When PyPSA-USA ingests this file, it adds lines and transformers separately. The pu/base unit conversions are the same, though?

pypsa-usa/workflow/scripts/build_base_network.py

Lines 73 to 101 in 338af99

	def add_branches_from_file(n: pypsa.Network, fn_branches: str) -> pypsa.Network:
	branches = pd.read_csv(
	fn_branches,
	dtype={"from_bus_id": str, "to_bus_id": str},
	index_col=0,
	).query("from_bus_id in @n.buses.index and to_bus_id in @n.buses.index")
	branches.loc[branches.rateA == 0, "rateA"] = 0.01
	for tech in ["Line", "Transformer"]:
	tech_branches = branches.query("branch_device_type == @tech")
	logger.info(f"Adding {len(tech_branches)} branches as {tech}s to the network.")
	# S_base = 100 MVA
	n.madd(
	tech,
	tech_branches.index,
	bus0=tech_branches.from_bus_id,
	bus1=tech_branches.to_bus_id,
	r=tech_branches.r * (n.buses.loc[tech_branches.from_bus_id]["v_nom"].values ** 2) / 100,
	x=tech_branches.x * (n.buses.loc[tech_branches.from_bus_id]["v_nom"].values ** 2) / 100,
	b=tech_branches.b / (n.buses.loc[tech_branches.from_bus_id]["v_nom"].values ** 2),
	s_nom=tech_branches.rateA,
	v_nom=tech_branches.from_bus_id.map(n.buses.v_nom),
	interconnect=tech_branches.interconnect,
	type="temp", # temporarily then over ridden by assign_line_types
	carrier="AC",
	underwater_fraction=0.0,
	)
	return n

The line calculations seem fine, however, PyPSA uses percentages of the nominal power ranking to describe x and r for transformers?

https://github.com/PyPSA/PyPSA/blob/c45f75089d22bc9972a9500929dd7b854acdd9fb/pypsa/network/power_flow.py#L773-L785

Therefore, when PyPSA calculates the pu value, wont they be off?

I don't have a processed PyPSA-USA/TAMU network on hand to check! So apologies if I am just missing a conversion somewhere.

Steps To Reproduce

No response

Error Message

Anything else?

No response

[trevorb1]

Sorry, got confused (again) between the PyPSA internal calculations and the TAMU units. Ignore this!

[trevorb1]

Sorry to go back and forth on this. But I think this actually is an issue. We should be multiplying by TAMU rateA then diving by the base MVA? ie.

r=tech_branches.r * tech_branches.rateA / 100
x=tech_branches.x * tech_branches.rateA / 100
b=tech_branches.b / tech_branches.rateA * 100