The Transmission Line Analyzer runs the full NESC / NERC / IEEE compliance and engineering suite on overhead lines — sag-tension, clearance, thermal rating, EMF, structure loading, vegetation, IEEE 516 live-line work, and blowout — against the same in-process FeatureServer your PLS-CADD structures and conductors land on. Findings are editable features, scenarios are versioned, and compliance evidence exports in one click. No more hopping between PLS-CADD, a separate clearance tool, and a GIS.
Every analysis shares the same shape: pick a span selection, pick a weather case, click Run. The job lands in the job table with status pending → running → succeeded | failed; results become findings in the findings FeatureLayer at the violation location.
| Analysis | Standard / method | Output |
|---|---|---|
| Sag | Catenary (Roon + Black) | Sag curve overlay + max-sag finding if > NESC limit |
| Clearance | NESC Table 232-1 | Vertical, horizontal, and cross-arm clearance violations |
| Thermal | IEEE 738-2012 | Ampacity rating + thermal limit findings |
| EMF | Biot-Savart + Maxwell potential coefficients | Phasor-summed B (µT) + E (V/m) contour overlay + threshold findings |
| Structure | NESC Grade B / C loading | Wind + ice + broken-wire overload findings |
| Vegetation | NERC FAC-003 + NESC Table 3 | Grow-in + fall-in vegetation encroachment findings |
| IEEE 516 | IEEE 516 mad-range table | Live-line work minimum approach distance findings |
| Blowout | Swing angle + CIGRE galloping ellipse | Mid-span contact + blowout findings |
Each analysis is a pure C# engine under Src/LocalMapServer/Transmission/Engines/ — no external services, no per-run cloud calls. The full NESC / NERC / IEEE lookup tables are baked in (NescClearanceTable, NercFac003Table, Ieee516MadTable).
VoltGrid doesn't reinvent the math. Every transmission engine implements a recognized industry standard — the same formulas your engineers already trust, with the cited clauses baked into the code. Findings carry the standard reference, so audit evidence points at NESC Rule 232-1 or IEEE 516-2021 §5.3, not "VoltGrid's clearance number."
| Standard | Clause / section | What VoltGrid computes | Implementation |
|---|---|---|---|
| NESC 2023 Table 232-1 |
Rule 232-1 ground clearances | 24 hardcoded clearance values — 6 voltage classes (≤0.75 / 0.75–22 / 22–69 / 69–230 / 230–500 / 500+ kV) × 4 crossing types (Road, Pedestrian/driveway, Railroad, Navigable water). Operator overrides flow through scenario payloads. | NescClearanceTable.cs ClearanceEngine.cs ComplianceReportGenerator.cs |
| NESC Grade B / C Loading |
Grade B & C structure loading (heavy district) | Wind + radial ice + conductor weight → vertical / transverse / resultant load per phase; RBS utilization %; NESC heavy-loading defaults (430 Pa wind, 12.7 mm ice for Grade B). | StructureEngine.cs |
| IEEE 738-2012 Thermal rating |
Steady-state thermal rating | Full heat-balance equation q_c + q_r = q_s + I²R: two forced-convection Nusselt correlations + Grashof natural convection + Stefan-Boltzmann radiative cooling + solar heating; Newton-Raphson conductor-temperature solver; 15-min & 30-min emergency ratings. |
ThermalEngine.cs |
| IEEE 516-2021 Live-line work |
§5.3 — Minimum Approach Distance | Phase-to-ground MAD lookup across 16 voltage-class rows × 3 work categories (bare-hand / hot-stick / insulated-gloves); exponential altitude correction factor (Table 5) applied above 1000 m. | Ieee516Engine.cs Ieee516MadTable.cs |
| NERC FAC-003 Vegetation |
Transmission vegetation management | Per-tree Border Zone / Danger Zone / Fall-in categorization against your utility's distance table; priority rollup (critical / high / medium / low) across the corridor; 3D distance + tree-height effective-reach computation. | NercVegetationEngine.cs NercFac003Table.cs |
| CIGRE Galloping |
Empirical conductor galloping ellipse | Swing angle arctan(F_wind / W) with insulator displacement; ice-amplified galloping ellipse (semi-major 0.3·sag·iceFactor, semi-minor 0.1·sag·iceFactor) for mid-span contact analysis. |
BlowoutEngine.cs |
| EPRI / IEEE 644 EMF |
Magnetic & electric field measurement methodology | Phasor-summed magnetic field via Biot-Savart (µ₀ · I · √bundleCount / 2π·r); electric field via Maxwell potential-coefficient matrix (Gaussian elimination) with single-image complex-image method; lateral profile sweep. | EmfEngine.cs |
| Roon & Black Sag-tension |
Catenary / parabolic sag approximation | Mid-span sag w · L² / (8·T) with linear thermal correction; catenary curve sampling; max-sag finding against NESC limit. (Parabolic approximation — valid for sag/span < 10%.) |
SagEngine.cs |
| NESC 2023 Plan & Profile |
Plan-profile sheet generation | Composes Sag + Clearance + NescClearanceTable output into a structured Plan/Profile JSON (1:5000 H, 1:500 V, 5× vertical exaggeration) for PDF rendering — engineering scale compliant. | PlanProfileGenerator.cs CrossSectionGeometry.cs |
ClearanceTableCache. NERC FAC-003 distances are operator-seeded — they're utility-specific (vegetation growth rates, local growth cycles, MVCD policy), so VoltGrid reads them from your GPKG rather than assuming a national default. Seed once; every subsequent NERC FAC-003 run uses your numbers.
All standard clauses and table values cited above are documented in the engine source files' header comments and reproducible from Src/LocalMapServer/Transmission/Engines/. Verify against your published standard editions before any compliance submission.
Load structures + conductors from a FeatureLayer, or import PLS-CADD CSV / GeoJSON / Shapefile / FGB / GeoParquet / GPKG directly. Everything lands in the same transmission.gpkg.
Click / box / polygon / named-set selection. Saved selections live in the selection_set table — re-use a span group across every analysis.
Pick weather case (NESC Grade B / C seeded, add your own) + conductor (7 industry conductors seeded: ACSR Drake / Cardinal / Bluebird / Dove / Mallard, AAC Poppy, ACSS Drake). Click Run.
Findings list with filters, status board, and the native Editor widget (create / edit / delete / attach). Promote to work orders or mission tasks directly from a finding.
Scenarios version every analysis run through draft → review → approved → superseded. The KPI dashboard, timeline, compliance view, and report exporter turn a season of corridor work into a single defensible artifact for NERC, state PUC, and internal audit.
Active findings by severity, by analysis type, by span — across the active scenario. Trend the count over time.
Draft → review → approved → superseded. Compare scenarios side-by-side; never lose a prior compliance snapshot.
One-click NERC FAC-003 / NESC / IEEE 516 evidence packs — findings, span list, weather case, conductor, calc method, sign-off.
Elevation resolver walks three tiers: (1) operator-supplied local DEM (LiDAR GeoTIFF), (2) served ImageServer (USGS 3DEP / enterprise DEM), (3) ArcGIS world elevation service. Pick the accuracy you need per run.
Import structures + conductors in one click, then run sag, clearance, vegetation, and live-line clearances against them — no manual GIS re-entry.