Calculator #004 IEC 60287 series IEC 60228 / 60502 IEC 60949 SC UAE · GCC · UK · EU

Cable Ampacity — continuous current rating

Continuous current rating I_z of power cables per IEC 60287-1-1, -1-2, -1-3, -2-1, -2-2 and -3-1. Skin and proximity effects, dielectric losses, sheath and armour loss factors, thermal resistances T₁…T₄, conductor-temperature back-calculation at user load, thermal short-circuit withstand per IEC 60949. Direct-buried and in-air installations, regional defaults for UAE / GCC / UK / EU.

Developed by the ieccalc.com engineering team

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PRO Multi-cable trench cross-section CAD — free · full report is PRO. The graphical layout editor below (soil layer stack with drag-to-reorder, mutual heating, λ₁ screen-loss, two-zone backfill T₄, conductor-temperature heatmap) is open to everyone. A licence adds the full .docx report: IEC 60502-2 Annex B cross-validation grid, distances matrix, per-cable derivation and the embedded canvas snapshot.

Cable Ampacity — Trench CAD multi-cable cross-section · IEC 60287 · Neher-McGrath

45%

Trench

Left

Right

Depth

Freq

Add

IEC 60502-2 Annex B

Buried direct, screens bonded both ends

Table

Size mm²

Voltage

Arrangement

Depth

ρ soil

T °C

Circuits (B.19)

Demo example. Editing of cables, layers and IEC presets is locked for the showcase. Calculate works on the example below; Download PRO below produces a watermarked EXAMPLE report. Upgrade to a paid licence to unlock editing and clean reports.

LMB: pan/drag · Shift: box · Scroll: zoom · Del: delete · Click layer · Drag boundary to swap

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FREE Single cable, parametric input. IEC 60287 closed-form ampacity, conductor-temperature back-calc at user load, IEC 60949 short-circuit withstand, compact .docx report. Always visible — every visitor of ieccalc.com sees this section.

1 — Cable construction

Conductor material Cross-section S [mm²] (IEC 60228)

Number of cores Conductor design

Insulation Rated voltage U₀/U [kV]

Metallic sheath / screen Armour

Outer covering / jacket Construction style

2 — Installation

Installation method Burial depth L [m] (axis to surface)

Formation (single-core only) Centre-to-centre spacing s [mm] (if spaced) 0 = touching (use cable diameter)

Number of circuits in trench / formation Circuit-to-circuit spacing [mm]

Soil thermal resistivity ρ_T,soil [K·m/W] Reference ambient temperature [°C] Soil temp at burial depth (buried) or air temp (in air)

Sheath / screen bonding Daily load factor μ (cyclic, IEC 60853) 1.0 = continuous; lower for cyclic loads (placeholder, full IEC 60853 in v2)

3 — Operating conditions

System frequency [Hz] Max conductor temperature θ_c,max [°C] Auto-set from insulation; override if applicable

Required load current I_load [A] (for verdict) 0 = skip verdict (just compute I_z) System voltage U [kV] (for active power calc)

Short-circuit current I"_k [kA] (RMS, sym.) 0 = skip SC withstand check Fault clearance time t_SC [s]

4 — Advanced overrides (optional)

By default all dimensions are estimated from IEC 60228 + IEC 60502 typical values. Override here if you have a specific cable datasheet.

Conductor diameter d_c [mm] 0 = auto (IEC 60228 max) Insulation thickness t₁ [mm] 0 = auto (IEC 60502 typical)

Sheath thickness t_s [mm] 0 = auto (typical for material) Outer jacket thickness t₃ [mm] 0 = auto

External cable diameter D_e [mm] 0 = computed from layers Sheath ρ₂₀ [Ω·mm²/m] (override) 0 = use library value

Skin coefficient k_s override 0 = use design default Proximity coefficient k_p override 0 = use design default

A — Steady-state ampacity I_z

Continuous current rating I_z —A

Active power transferable (3-φ)

—

Conductor max temperature θ_c,max

—

Reference ambient θ_amb

—

Allowed temperature rise Δθ

—

Number of load-carrying cores n

—

B — Loss components (per metre, per phase)

DC resistance R₂₀ @ 20 °C

—

DC resistance R' @ θ_c,max

—

Skin-effect factor y_s

—

Proximity-effect factor y_p

—

AC resistance R

—

Dielectric capacitance C

—

Dielectric loss W_d

—

Sheath loss factor λ₁

—

Armour loss factor λ₂

—

Conductor loss W_c at I_z

—

Sheath loss W_s at I_z

—

Armour loss W_a at I_z

—

Total losses W_t at I_z

—

C — Thermal resistances

T₁ insulation [K·m/W]

—

T₂ bedding (sheath ↔ armour) [K·m/W]

—

T₃ outer covering [K·m/W]

—

T₄ external [K·m/W]

—

Estimated cable diameter D_e [mm]

—

Conductor diameter d_c [mm]

—

Insulation thickness t₁ [mm]

—

Sheath ext. dia D'_s [mm]

—

Geometric u = 2L/D_e

—

D — Conductor temperature at user load

θ_c at I_load —°C

Conductor loss W_c(I_load)

—

Sheath loss W_s(I_load)

—

Total losses W_t(I_load)

—

Margin to limit θ_c,max

—

Verdict

—

E — Thermal short-circuit withstand (IEC 60949)

k constant (initial→final, material/insulation)

—

Permissible adiabatic I·√t [kA·√s]

—

Permissible I_SC for given t_SC

—

Permissible time at given I"_k

—

Verdict

—

F — Project completeness & overall verdict

Item	Status

—

Formulas & methodology — IEC 60287 / IEC 60949

I = √( (Δθ − W_d·[½T₁ + n·(T₂+T₃+T₄)]) / (R·T₁ + n·R·(1+λ₁)·T₂ + n·R·(1+λ₁+λ₂)·(T₃+T₄)) )

Continuous current rating per IEC 60287-1-1 Eq. 1 (100 % load factor).

θ_c = θ_amb + W_d·(½T₁ + n(T₂+T₃+T₄)) + I²R·(T₁ + n(1+λ₁)T₂ + n(1+λ₁+λ₂)(T₃+T₄))

Conductor temperature back-calculation at user load — same Eq. 1 solved for θ_c at given I.

I_SC,perm = k · S / √t_SC

Adiabatic thermal short-circuit withstand per IEC 60949 §3.1; k constant is material/insulation specific.

Validation tests (IEC 60287 worked examples + reciprocal checks)

Click "Run validation" below to execute the test suite.

Standards used: IEC 60287-1-1:2023 — Current rating equations, general; · IEC 60287-1-2:2023 — Sheath eddy-current losses for special bonding; · IEC 60287-1-3:2023 — Current sharing in parallel single-core cables; · IEC 60287-2-1:2023 — Thermal resistance, calculation; · IEC 60287-2-2 — External thermal resistance, methods; · IEC 60287-3-1 — Reference operating conditions and selection of cable type; · IEC 60228:2004 — Conductors of insulated cables; · IEC 60502-1, -2 — Power cables with extruded insulation 1 kV ≤ U_m ≤ 36 kV — typical insulation thicknesses; · IEC 60949:1988+A1:2008 — Calculation of thermally permissible short-circuit currents; · IEC 60364-5-52 — Selection and erection — current-carrying capacities (cross-check). · Bonding factors per CIGRE TB 283 / 415 / 797.

What this tool computes: the single cable or circuit parametrically, and the multi-cable trench from its actual geometry — IEC closed-form ampacity, conductor-temperature back-calculation, IEC 60949 short-circuit withstand. Tabulated grouping correction factors are not used in the multi-cable trench model. The mutual thermal influence between cables is calculated directly from the IEC 60287 thermal model on the real cable arrangement and trench geometry: the neighbours’ contribution to T₄ per IEC 60287-2-1 §2.2.3.1, and the two-zone backfill per §2.2.7.2. Not implemented in this version, at either tier: cyclic ratings per IEC 60853, in-duct configurations, and cross-bonded sheath eddy-current losses per IEC 60287-1-2.