add icd to ybus build

[m-bossart]

Requires:

• add icd files PowerSystemsTestData#118
• add icd cases PowerSystemCaseBuilder.jl#193

[m-bossart]

The tolerance seems too high I need to make sure the tests are correct before review

[github-actions]

Performance Results

Precompile Time

Main	This Branch	Delta
2.1 s	2.1 s	+2.5%

Execution Time

Cells show median (min–max) over 5 samples; delta compares medians.

Test	Main	This Branch	Delta
matpower_ACTIVSg2000_sys-Build Ybus	9.5 (9.3–11.4) ms	9.2 (9.0–17.3) ms	-2.8%
matpower_ACTIVSg2000_sys-Build PTDF	75.6 (74.4–78.0) ms	74.1 (73.3–74.7) ms	-2.0%
matpower_ACTIVSg2000_sys-Build LODF	140.4 (136.6–141.5) ms	136.0 (135.7–137.5) ms	-3.1%
matpower_ACTIVSg2000_sys-Build VirtualMODF	90.4 (88.9–90.8) ms	918.5 (912.1–921.2) ms	+916.5%
matpower_ACTIVSg2000_sys-VirtualMODF Query 10 rows	0.6 (0.5–1.4) ms	0.6 (0.5–1.5) ms	+1.5%
matpower_ACTIVSg2000_sys-Radial network reduction	0.7 (0.7–0.8) ms	0.7 (0.7–0.9) ms	+4.3%
matpower_ACTIVSg2000_sys-Degree two network reduction	FAILED	FAILED	N/A
Base_Eastern_Interconnect_515GW-Build Ybus	524.3 (518.8–527.7) ms	492.9 (486.1–506.5) ms	-6.0%
Base_Eastern_Interconnect_515GW-Build VirtualPTDF	767.8 (764.1–769.4) ms	729.8 (723.9–733.3) ms	-5.0%
Base_Eastern_Interconnect_515GW-VirtualPTDF Query 10 rows	24.8 (24.2–25.3) ms	24.7 (23.9–24.8) ms	-0.5%
Base_Eastern_Interconnect_515GW-Build VirtualMODF	775.3 (772.4–778.6) ms	802.5 (797.5–807.7) ms	+3.5%
Base_Eastern_Interconnect_515GW-VirtualMODF Query 10 rows	29.3 (29.0–29.6) ms	30.9 (30.2–32.0) ms	+5.4%
Base_Eastern_Interconnect_515GW-Radial network reduction	36.2 (35.8–38.0) ms	37.3 (36.2–38.8) ms	+3.1%
Base_Eastern_Interconnect_515GW-Degree two network reduction	FAILED	FAILED	N/A

[m-bossart]

@jd-lara the tests are passing locally for me with main of PowerSystemCaseBuilder. This is ready for review

[Copilot]

Pull request overview

This PR adds support for applying PSS/E Impedance Correction Data (ICD/ICT) when constructing the AC Ybus, and updates the PSS/E regression tests + fixtures to validate the corrected transformer admittances (including off-nominal cases).

Changes:

• Compute ICD correction factors from PSY.ImpedanceCorrectionData curves and apply them by scaling transformer series impedance during Ybus assembly.
• Precompute a per-transformer correction map and thread the correction factor through branch iteration into _ybus!/ybus_branch_entries.
• Update existing PSS/E Ybus comparisons to use Float32-relative tolerances and add two new PSS/E fixture matrices for ICD-enabled/disabled modified 14-bus cases.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 6 comments.

Show a summary per file

File	Description
src/Ybus.jl	Adds ICD curve interpolation + correction-factor plumbing into transformer Ybus contributions, plus new tests-facing assembly paths (currently with a broken adj plumbing that needs fixes).
src/YbusACBranches.jl	Introduces ICDCorrectionMap and extends branch iteration to supply a per-branch correction factor.
test/test_ybus_psse.jl	Tightens numeric comparisons to Float32-relative tolerances and adds new testsets covering off-nominal and nominal ICD cases.
test/test_data/modified_14bus_system_off_nominal_icd_ymatrix.txt	New PSS/E Y-matrix fixture for the off-nominal ICD case.
test/test_data/modified_14bus_system_no_icd.txt	New PSS/E Y-matrix fixture for the nominal/no-ICD case.

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[m-bossart]

@jd-lara this is ready for review. The tests pass locally with PowerSystemCaseBuilder#main which has the new test system but is not yet released.