2025 NERC region and PRM update

[clairehalloran]

Summary

Updates NERC regions and PRM values based on 2025 LTRA values. This should primarily impact runs with GSw_PRM_CapCredit=1 and GSw_PRM_scenario=nerc. Small impact on other runs due to switching firm transfer limits to the transreg level from the nercr level.

Technical details

NERC split the former WECC-Northwest region into 3 regions: WECC-Northwest (winter-peaking), WECC-Basin (summer-peaking, lower reference margin), and WECC-Rocky Mountain (summer-peaking, higher reference margin):

Most of Nevada is now in NERC-Southwest, rather than NERC-Northwest. The nercr column in the hierarchy files has been updated to include these changes.

Most notably, the margin in PRM increased and now escalates for each future year. Margins also increased slightly in NPCC_NE and WECC_CA and decreased slightly in MISO. WECC_SW now has slightly higher margin, but the region shifted to include most of Nevada.

Region	Year	2026	2027	2028	2029	2030	2031	2032	2033	2034	2035
MISO	2024 LTRA	9.4	9.6	9.5	9.4	9.4	9.5	9.6	9.7	9.7	N/A
	2025 LTRA	8.1	8.3	8.5	8.5	8.5	8.6	8.7	8.8	8.9	8.9
NPCC_NE	2024 LTRA	11.8	11.3	11.3	11.3	11.3	11.3	11.3	11.3	11.3	N/A
	2025 LTRA	13.4	13.0	13.0	13.0	13.0	13.0	13.0	13.0	13.0	13.0
PJM	2024 LTRA	17.7	17.7	17.6	17.6	17.6	17.6	17.6	17.6	17.6	N/A
	2025 LTRA	18.6	20.1	21.9	23.9	26.3	28.9	30.8	33.0	35.1	35.1
WECC_CA	2024 LTRA	17.4	17.4	16.4	17.4	16.6	16.1	16.3	14.9	15.3	N/A
	2025 LTRA	20.3	19.2	19.3	19.7	19.3	19.1	18.9	17.8	18.3	18.0
WECC_NW (old)	2024 LTRA	15.8	15.9	15.4	14.7	14.5	14.3	14.3	14.4	13.8	N/A
WECC_BA (new)	2025 LTRA	13.5	14.0	13.6	12.4	12.3	12.1	12.1	12.5	11.8	11.8
WECC_RM (new)	2025 LTRA	17.8	17.0	16.2	16.1	15.7	15.2	13.5	11.9	14.1	13.9
WECC_NW (new)	2025 LTRA	17.8	17.4	16.1	15.8	15.5	15.3	15.9	15.0	14.9	14.8
WECC_SW (old)	2024 LTRA	10.8	12.0	11.7	10.2	10.1	9.9	9.7	10.8	9.4	N/A
WECC_SW (new)	2025 LTRA	13.3	13.7	13.6	12.6	12.2	12.0	11.7	12.3	11.3	11.1

This PR applies firm transfer limits at the transreg level rather than the nercr level since FERC regions seem to change less often. This also matches the FERC Order 1000 regions used in the current source of historical interregional transfer capability by region, Table 2 of ESIG's Interregional Transmission for Resilience report. Peak net imports are taken from the "Coincident Interregional Transfer Capacity" column, and MW_TotalDemand values are taken from the "Peak Demand" column. The maps below compare the FERC regions (planning regions) with the LTRA 2024 NERC regions:

In effect, this change allows firm transfers between different NERC regions in SERTP and lets WestConnect North (CO, eastern WY, and western SD) to transfer firm capacity with WestConnect South (AZ and most of NM), rather than NorthernGrid.

Additional changes

• Replaces the z69 zones with the z70 zones, splitting ID into ID_BA and ID_NW to maintain NERC region boundaries.
• Removes the ramp2025_20by50 column of prm_annual.csv.

Relevant sources or documentation

Validation, testing, and comparison report(s)

Checklist for author

Details to double-check

• Charge code provided to reviewers
• Included comparison reports for appropriate test cases
• Documentation updated if necessary
• If input data added/modified:
  • Dollar year recorded and converted to 2004$ for GAMS
  • Timeseries are in Central Time
  • Units are specified
  • Preprocessing steps have been documented and committed to ReEDS_Input_Processing
  • New large data files handled with .h5 instead of .csv
  • If spatially resolved inputs are modified, the following visualizations for each file are included in the PR description (time-averaged if the inputs are time-resolved):
    • Map of absolute values before
    • Map of absolute values after
    • Map of differences: (after - before) or (after / before)
• Code formatting standardized
• Reusable functions used where possible instead of copy/pasted code

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 (runbatch.py, d_solve_iterate.py)
• No change to code organization
• No change to package requirements (environment.yml or Project.toml)

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