Research — Circuit / Grounding · Live
Ampacity, fault current, grounding and sheath-bonding calculations — two anchored to published examples.
Typed calculation functions for distribution-side electrical engineering: conductor and underground-cable ampacity, symmetrical-components fault current, IEEE 80/81 grounding, and cable sheath induced voltage and circulating-current loss. Each result carries provenance (cited method, version, timestamp) and the functions compute values without judging acceptability.
IEEE 80 · IEEE 81 · IEEE 1453 · NEMA MG 1
Interactive demos
- Feeder protection: fault slide →Drag a bolted fault along a 12.47 kV feeder: the current falls, the relay trips later along its time-current curve, and the cable's withstand line shows where the data says the cable exceeds its withstand. Six stories show the fixes. Draft, unvalidated; withstand values unverified.Auto ▶
- Grounding grid: touch and step →A 60 m square substation grid in plan and section: press Fault and watch the touch-voltage field flood the corner meshes while mesh and step voltage bars move against the 50 or 70 kg tolerable limits. Draft, unvalidated.Auto ▶
- Conductor ampacity →Slide ambient, wind speed and angle, and the conductor limit for a Drake ACSR line and watch the IEEE 738 heat balance set the ampacity. Computes a value, no verdict. Draft, unvalidated.Auto ▶
- Fault current along a feeder →Slide a bolted fault out a 12.47 kV feeder and compare three-phase, line-to-line and single line-to-ground current. Internal self-consistency only.Auto ▶
Harnesses in action
Scripted chat-and-viewer examples where this domain's harness is one of the tools. Illustrative, not live sessions.
- Grid to rack: one design, six harnesses →Illustrative, scriptedA grid-fed datacenter reviewed stage by stage: transmission tap line, substation bus scheme and fence, duct bank, hall power path, service-gear fault current against its interrupting rating, and liquid cooling. Each stage hands a result to the next.
- Why the shared graph matters →Illustrative, scriptedA DER interconnection request screened with and without a shared entity graph: generation, feeder and substation harnesses joined through one graph. The circuit harness supplies fault current, and an upstream breaker count comes from the substation harness. One join is shown as planned, not wired.
What it can do
calculate_conductor_ampacitySteady-state bare overhead conductor ampacity from ambient, wind, solar and max conductor temperature (IEEE 738).
calculate_underground_cable_ampacityIEC 60287-1-1 / Neher-McGrath ampacity for a single direct-buried cable.
calculate_available_fault_currentThree-phase, line-to-line and single-line-to-ground fault current from a source plus path impedance.
calculate_grounding_grid_resistanceGrid resistance using Sverak’s formula, IEEE Std 80-2013.
calculate_ground_potential_riseDecrement factor, grid current and ground potential rise.
calculate_sheath_bonding_loss_factorIEC 60287-1-1 circulating-current sheath loss factor for solidly bonded cables.
A worked case
Input
Drake 795 kcmil 26/7 ACSR at 100 °C max conductor temperature, 40 °C ambient, 2 ft/s crosswind, solar flux 96 W/ft².
Result
The harness computes 980.5 A, which is 1.3% under the ~993 A that IEEE Std 738-2012 Annex B publishes for this case and inside the test’s ±10% band. Because the 100 °C limit is above the tabulated range, the conductor resistance is extrapolated, not interpolated, so even this one published anchor is partly extrapolated.
Where this stands
Draft; outputs should not feed compliance decisions until reviewed. Only conductor ampacity and the transformer hottest-spot function are anchored to an independent published reference; the grounding decrement and surface-layer factors each match one published point. Everything else is tested for internal self-consistency only.
Open questions
- Cable fault-withstand K factors are flagged unverified, with a likely non-conservative error left unchanged pending a primary source.
- No IEEE 80 Annex worked example could be recovered, so the grounding chain has no full independent benchmark.
- Sheath loss models circulating current only (no eddy, armour or cross-bonding) and is not yet composed into the ampacity function.