Improve equivalent transformation calculations in base.nc (#978)

* Keep an original voltage value before rebase

* Adjust the transmission capacity to account for the voltage rebase

* Adjust p_nom calculations for DC lines

* Add a release note

doc/release_notes.rst

@@ -18,8 +18,10 @@ E.g. if a new rule becomes available describe how to use it `snakemake -j1 run_t
 
 **Minor Changes and bug-fixing**
 
-* Minor bug-fixing for GADM_ID format naming. `PR #980 <https://github.com/pypsa-meets-earth/pypsa-earth/pull/980>`__
 
+* Keep data on the original voltage value when rebasing voltages to the standard values and adjust the transmission capacity accordingly. `PR #898 <https://github.com/pypsa-meets-earth/pypsa-earth/pull/978>`__
+
+* Minor bug-fixing for GADM_ID format naming. `PR #980 <https://github.com/pypsa-meets-earth/pypsa-earth/pull/980>`__
 
 PyPSA-Earth 0.3.0
 =================

scripts/base_network.py

@@ -451,6 +451,8 @@ def _rebase_voltage_to_config(base_network_config, voltages_config, component):
     config : dictionary (by snakemake)
     component : dataframe
     """
+    component["v_nom_original"] = component["v_nom"]
+
     v_min = (
         base_network_config["min_voltage_rebase_voltage"] / 1000
     )  # min. filtered value in dataset
@@ -494,9 +496,16 @@ def base_network(
     lines_dc = lines[lines.tag_frequency.astype(float) == 0].copy()
 
     lines_ac = _set_electrical_parameters_lines(lines_config, voltages_config, lines_ac)
+    lines_ac.num_parallel = lines_ac.num_parallel * (
+        lines_ac.v_nom_original / lines_ac.v_nom
+    )
+
     lines_dc = _set_electrical_parameters_dc_lines(
         lines_config, voltages_config, lines_dc
     )
+    lines_dc.num_parallel = lines_dc.num_parallel * (
+        lines_dc.v_nom_original / lines_dc.v_nom
+    )
 
     transformers = _set_electrical_parameters_transformers(
         transformers_config, transformers
@@ -518,7 +527,7 @@ def base_network(
         lines_dc = _set_electrical_parameters_links(links_config, lines_dc)
         # parse line information into p_nom required for converters
         lines_dc["p_nom"] = lines_dc.apply(
-            lambda x: x["v_nom"] * n.line_types.i_nom[x["type"]],
+            lambda x: x["v_nom_original"] * n.line_types.i_nom[x["type"]],
             axis=1,
             result_type="reduce",
         )