Update interzonal transmission costs/distances and use directly calculated values by patrickbrown4 · Pull Request #95 · ReEDS-Model/ReEDS

patrickbrown4 · 2026-05-15T23:13:22Z

Summary

In the same vein as 2003, this PR:

Adapts the interzonal transmission costs, distances, and planned/optional additions for spatial flexibility as laid out in Reformat spatial inputs pipeline for more flexibility #16
Uses the latest reV methods and assumptions to calculate the interzonal least-cost paths and costs

Technical details

Implementation notes

Least-cost paths

There are a few updates to the interzonal least-cost path procedure:

The interzonal transmission costs have been out of sync with interconnection costs since 1836. This PR brings them in sync, so both are now using costs from the MISO 2025 Transmission Cost Estimation Guide (parent, description, data)
- A new pair of data files from MISO, inputs/transmission/conductor_{ac or dc}.csv, provide lookup tables for converting from the assumed kV to MW capacity
We used to assume 500 kV costs for all interzonal greenfield lines, regardless of location or scale (so tiny counties with low-voltage lines got to use 500 kV costs, which are cheaper on a USD/MW basis than lower-voltage lines). Here, we instead use the maximum AC voltage currently connecting each pair of zones, with a 138 kV floor. So interfaces that are crossed by higher-voltage lines get lower USD/MW expansion than interfaces crossed by lower-voltage lines.

Spatial flexibility

The old future-capacity scenarios (which were specific to z134) have been removed. The scenarios used in NTP have been maintained (planned_lines-NTP_{MT or P2P}.csv), but now specify individual from/to endpoints
Similarly, planned additions are now specified as individual endpoints
- TransWest Express and SunZia have been added; see the descriptions in inputs/transmission/README.md
- The offshore zone backbones are in inputs/transmission/newlinks_offshore_backbone.csv
- The offshore zone radial connections are in inputs/zones/{GSw_ZoneSet}/newlinks_offshore_radial.csv
  - These need to be specified for each GSw_ZoneSet because the user might want to control which zone they make landfall in, particularly at county resolution
  - Offshore zones and county resolution are now compatible (they were not before)
We keep the old single-bin transmission upgrade supply curve (TSC) file for greenfield 500 kV with GSw_ZoneSet=z134 as an example of the required file format when using TSC, but will eventually remove it when we add a full supply curve
- The greenfield costs are put into this format automatically in transmission.py

Additional changes

Features that we no longer need with the new format have been removed:
- inputs/shapefiles/transmission_endpoints (now in inputs/zones/{GSw_ZoneSet}/zonehash.csv)
- Transmission aggregation functionality in copy_files.py and aggregate_regions.py
- Zone aggregation functionality in reeds.io.get_zonemap()
transmission.py has been reorganized to make it importable
min_co2_spurline_miles (= 20): moved from hard-coded in transmission.py to scalars.csv

Switches added/removed/changed

GSw_TranScen: Allowable options changed to none (default, meaning only interfaces with existing capacity can be expanded), NTP_MT, or NTP_P2P

Issues resolved

Known incompatibilities

WECC_county is failing because we're missing the cost/distance for the newly added SunZia line at that resolution. I'll ask the reV team for it the next time we run more paths (it's more efficient to do in a batch), but since the WECC_county case was already failing the last time I checked (in PR 2003), I'm not sure it's worth delaying this PR for it. But let me know if you disagree and I can ask them to run it now.

Validation, testing, and comparison report(s)

Here's some background info and plots of the new costs: 20260515 - transmission costs distances.pptx

I'll add compare reports to that deck as they come in.

Checklist for author

Details to double-check

General information to guide review

Zero impact on results of default case
No large data file(s) added/modified
No substantive impact on runtime for full-US reference case
No substantive impact on folder size for full-US reference case
No change to process flow (runreeds.py, reeds/core/solve/solve.py)
No change to code organization
No change to package requirements (environment.yml or Project.toml)

Did you use LLM tools (chatbot or copilot) in the preparation of this PR? If so, describe how

No

…ogging style

…ines-{}.csv

…; only define co2_routes for r,rr pairs with nonzero distance

…thout an interfaces list

…ap() (no longer need to modify zone map in aggregate_regions.py)

… the cost and length of too-straight lines in transmission.py accordingly

…cost_ac for R2X

patrickbrown4 · 2026-05-19T18:59:34Z

Removed because the versions that match the interzonal paths are in the zonehash.csv files; these no longer match

patrickbrown4 · 2026-05-19T19:01:00Z

Included so we can avoid adding more 'MW' or '$/MWmile' columns to the already-large transmission_cost_distance.csv; instead we just look it up from here using the voltage column

patrickbrown4 · 2026-05-19T19:02:28Z

The "name" column doesn't actually matter but including it here in case it's useful for backwards compatibility

patrickbrown4 · 2026-05-19T19:03:32Z

not directly related but was deferred earlier and it's on the list for #37

patrickbrown4 · 2026-05-19T19:03:55Z

patrickbrown4 · 2026-05-19T19:08:51Z

+    return offshore_zones
+
+
+def get_zonemap(case=None, exclude_water_areas=False, crs='ESRI:102008', **kwargs):


Updated to use the new zone node lat/lons and avoid need for county/mixed-specific processing

patrickbrown4 · 2026-05-19T19:10:53Z

-GSw_TransSquiggliness,Transmission distance multiplier to approximate the squigglier paths followed by actual lines (only applied to NEW lines),float,1,
-GSw_TransUpgradeMethod,Method for calculating AC transmission upgrade costs,500kv,500kv,
+GSw_TransScen,Additional candidate interfaces for transmission expansion between zones,^(none|NTP_(MT|P2P))$,none,
+GSw_TransSquigglinessMin,Minimum squiggliness (straight-line length multiplier) to apply for interzonal transmission; the default value is from the MISO Transmission Cost Estimation Guide (https://www.misoenergy.org/planning/transmission-planning/mtep),float,1.3,


The new routes are even straighter than the old, so I think now is a good time for this change (and it keeps us more aligned with MISO assumptions)

patrickbrown4 · 2026-05-19T19:13:21Z

+    scalars = reeds.io.get_scalars(case)
+
+    interface_params = reeds.inputs.get_distances(case)
+    ## Apply the minimum-squiggliness factor


This part is new; most of the rest is just reorganized

patrickbrown4 · 2026-05-19T19:15:09Z

-    # Mixed resolution procedure
-    if agglevel_variables['lvl'] == 'mult':
-        ### Model zones
-        dfba = gpd.read_file(os.path.join(reeds_path, 'inputs', 'shapefiles', 'US_PCA'))


With this change, we're no longer using this 134-zone shapefile directly. We can wait and remove it in a future PR though, since there might be upstream or downstream processes relying on it.

patrickbrown4 · 2026-05-19T19:18:03Z

        [['r', 'rr', 'MW_forward', 'MW_reverse']]
        .assign(trtype='AC')
    )
-    ### DEPRECATED: p19 is islanded with NARIS transmission data, so connect it manually


Dropped because we only calculate AC distances/costs for interfaces crossed by existing AC lines and this one is not crossed by any lines. So I think p19 is now islanded, but I didn't have any issues with extra ReEDS/PRAS iterations there (and we're now only ~2 PRs away from switching to 90 zones).

patrickbrown4 · 2026-05-20T16:25:39Z

+    dfcounty['r'] = county2zone
+    dfzones = dfcounty.dissolve('r')


Because this zone map is built from the county map, which is more detailed than the old US_PCA map, all the downstream calculations and plots that use the maps (accessed via reeds.io.get_dfmap() or maps.gpkg) are slowed down. There is a .simplify_coverage() function in geopandas 1.1 that we can use to simplify the geometry and speed them all up again, but it requires an update to the conda environment.

Elaine is also working on a gdxpds update; my plan is to go ahead with the current implementation for now, and then once the new gdxpds version is ready, do a holistic environment update to geopandas 1.1 / pandas 3 / python 3.14 / etc., so everyone only has to update their environment once.

One other package that might be worth adding in an update is the highs package to give access to the HiGHS solver for things like representative period selection.

…ault setting to acsr

…sion docs

wesleyjcole · 2026-05-27T14:42:08Z

-Network reinforcement costs are approximated by tracing a path along existing transmission lines from each wind/solar POI to each zone "center" within the same state;
-the zone center is usually taken as the largest population center in the model zone but is sometimes (for zones without large urban centers) assigned to a high-voltage substation within the zone.[^ref35]
-A cost for each reinforcement route is calculated using the cost surface described above, with capital expenditure (CAPEX) costs multiplied by 50% to approximate the lower cost for reconductoring compared to greenfield transmission construction.
+Network reinforcement costs are approximated by tracing a path along existing transmission lines from each wind/solar POI to a nearby urban center.


Can you quantify "nearby" and "urban center"? I can't remember the specifics, but this seems like a good place to document those.

wesleyjcole · 2026-05-27T14:50:04Z

@@ -0,0 +1,9 @@
+voltage_kv,kcmil,conductor_type,conductor_quantity,amp


What is kcmil?

It's a silly U.S. unit but it's the standard measurement of wire gauge: https://en.wikipedia.org/wiki/Circular_mil

wesleyjcole · 2026-05-27T14:54:36Z

-Cross Sound Cable,330,-72.90222222,41.28666667,-72.8675,40.95916667
-Neptune Cable,660,-73.55111111,40.76055556,-74.35308333,40.47371667
-Trans Bay Cable,400,-121.89666667,38.03083333,-122.38583333,37.75472222
+name,MW,year_online,trtype,certain,from_lon,from_lat,to_lon,to_lat


Is year_online the number of years until it is online? If so, it might be worth updating the name, as I was expecting something like "2028" for the value rather than "0".

Added a description to inputs/transmission/README.md and changed these to their actual historical online year

wesleyjcole · 2026-05-27T14:55:36Z

@@ -0,0 +1,3 @@
+name,MW,year_online,trtype,certain,from_lon,from_lat,to_lon,to_lat
+TransWestExpress,3000,2032,VSC,1,-107.176147,41.747242,-112.590781,39.541825


This one has year_online as what I would expect, so I think I'm not understanding this column correcting, or what a zero value for this column means.

wesleyjcole · 2026-05-27T17:43:36Z

+    ### TEMPORARY 20260402: Drop county interfaces with no distance/cost
+    if (level == 'r') and (sw.GSw_RegionResolution in ['county', 'mixed']):
+        transmission_line_fom = get_transmission_fom(case, interface_params)
+        indices = ['r', 'rr', 'trtype']
+        drop = (
+            dfout
+            .merge(transmission_line_fom.reset_index(), on=indices, how='left')
+        )
+        drop = list(drop.loc[drop.USDperMWyear.isnull(), indices].itertuples(index=False))
+        dfout = dfout.set_index(indices).drop(drop).reset_index()


Is this what is making WECC county runs fail (mentioned in your PR text)? Or does this make it not fail?

Yunzhi is nearly done with the WECC county bug fix, so it would be nice to not have it immediately broken again if that can be avoided, even if that meant a temporary patched solution until new reV data is available.

No, it's a bit different; this is to keep GSw_ZoneSet = z3109 (county-level, which includes counties with no transmission links to neighbors) working until we finish reformatting the spatial pipeline, which will allow use of GSw_ZoneSet = z2972 (which aggregates those counties into their neighbors and avoids making islanded zones).

The missing SunZia line at county resolution is caught in check_inputs.py. But I'll add it before merging.

…Detail = 1

…ME.md

patrickbrown4 added 30 commits April 15, 2026 10:52

copy branch from .gov repo

a536d1b

Merge branch 'main' into pb/transcost

c679d84

move scale_column() to reeds.output_calc to avoid propagating bokeh l…

b06f904

…ogging style

remove ba/county planned tranmission files and replace with planned_l…

0a3679f

…ines-{}.csv

transmission: propagate name changes

33920d0

transmission.py: move firm import limits to get_firm_import_limits()

760f3c8

transmission.py: use new data structures

620d6e2

add first newlinks_offshore_{}.csv files

46c0e37

add newlinks_offshore_radial.csv for other zone definitions

9a103c2

functify transmission.py

2ab5e98

remove transmission_endpoints shapefile

17df830

transmission.py: downselect to modeled regions; add leading *

0d3de04

move min_co2_spurline_miles to scalars; use DC distance for pipelines…

81c51b9

…; only define co2_routes for r,rr pairs with nonzero distance

add interfaces arg to inputs.get_interface_data() to allow reading wi…

c04e64a

…thout an interfaces list

define transmission_line_fom for both directions

5bb7d0e

include offshore links in transmission.py

e568e25

fix VA_W zonehash

d9410e4

validate_zoneset(): check for distances for all interfaces

04233e4

remove unused transmission aggregation options

3fd3d92

reeds.inputs.parse_regions(): convert to usual case and **kwarg inputs

44ce609

move get_zones() from reeds.inputs to reeds.io and simplify get_zonem…

e48d4b2

…ap() (no longer need to modify zone map in aggregate_regions.py)

add SunZia

3235e40

transmission.py: check for missing costs upfront; cleanup

f590f43

transmission_cost_distance.csv: add missing B2B connections

6d4f037

transmission.py: reorganize functions

a962c0f

add individual-line transmission costs & distances

c091f25

transmission.py: add missing docstrings

8adb7dc

Merge branch 'main' into pb/transcost

8b83e0b

retail rates: transmission_distance.csv -> transmission_miles.csv

b2b7cf7

transmission.py: don't add artificial p19-p20 link

ede6efa

patrickbrown4 added 3 commits May 18, 2026 16:51

change GSw_TransSquiggliness -> GSw_TransSquigglinessMin and scale up…

f9cb74f

… the cost and length of too-straight lines in transmission.py accordingly

transmission.py: write transmission_distance for retail rates and r2x

faf5afa

add GSw_TransConductor and conductor_ac_acsr.csv; write transmission_…

3befeb1

…cost_ac for R2X

patrickbrown4 commented May 19, 2026

View reviewed changes

patrickbrown4 commented May 20, 2026

View reviewed changes

patrickbrown4 mentioned this pull request May 20, 2026

Update conda environment #103

Draft

12 tasks

patrickbrown4 added 2 commits May 20, 2026 17:25

GSw_TransConductor: change 'default' to 'acss'; change the actual def…

6b42416

…ault setting to acsr

add plot_hvdc() and plot_voltage() to input_plots.py; update transmis…

333f789

…sion docs

patrickbrown4 marked this pull request as ready for review May 21, 2026 22:24

github-actions Bot added data_changes model_changes docs postprocessing switches labels May 21, 2026

patrickbrown4 added 6 commits May 21, 2026 16:25

Merge branch 'main' into pb/transcost

5e4651b

fix reeds2pras.process_lines() for zero-capacity VSC

6dd0420

include 'certain' transmission expansions in routes_inv()

e688fa1

add missing val_converter(r,t)s

2c51ae7

Merge branch 'main' into pb/transcost

21971fb

Merge branch 'main' into pb/transcost

6603bad

patrickbrown4 mentioned this pull request May 22, 2026

Disaggregate and re-aggregate inputs with regional scope of legacy (134) zones #102

Open

13 tasks

fix OR_water

cb02783

patrickbrown4 requested review from kodiobika and wesleyjcole May 22, 2026 21:28

patrickbrown4 added 2 commits May 26, 2026 09:53

fix reedsplots.plot_diff() for transmission

28503e7

speed up runstatus.py by avoiding reeds import

91e5f5d

wesleyjcole reviewed May 27, 2026

View reviewed changes

patrickbrown4 added 3 commits May 27, 2026 13:45

Merge branch 'main' into pb/transcost

91acfcf

runreeds.check_compatibility(): allow county resolution with GSw_CO2_…

e4c32cd

…Detail = 1

rename hvdc files for clarity; describe contents in transmission/READ…

8d3f490

…ME.md

		return offshore_zones


		def get_zonemap(case=None, exclude_water_areas=False, crs='ESRI:102008', **kwargs):

		@@ -0,0 +1,9 @@
		voltage_kv,kcmil,conductor_type,conductor_quantity,amp

		@@ -0,0 +1,3 @@
		name,MW,year_online,trtype,certain,from_lon,from_lat,to_lon,to_lat
		TransWestExpress,3000,2032,VSC,1,-107.176147,41.747242,-112.590781,39.541825

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Summary

Technical details

Implementation notes

Least-cost paths

Spatial flexibility

Additional changes

Switches added/removed/changed

Issues resolved

Known incompatibilities

Validation, testing, and comparison report(s)

Checklist for author

Details to double-check

General information to guide review

Did you use LLM tools (chatbot or copilot) in the preparation of this PR? If so, describe how

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patrickbrown4 commented May 15, 2026 •

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