EHV Cable Current Calculator – A Complete Calculation Tool

Calculate derated current ratings for XLPE EHV cables — 11 kV to 220 kV, 185 to 1200 mm² — per IEC 60287 & IS 3961 with full derating factors.

Calculate the derated continuous current rating of single-core XLPE EHV cables for 11 kV to 220 kV systems and 185 to 1200 mm² conductor sizes — based on IEC 60287-1-1 and IS 3961 (Parts 3 & 5). Select all parameters below and click Calculate.

Conductor Material

Copper (Cu) Aluminium (Al)

Number of Cores

Single-core Three-core

Three-core not typically used above 66 kV.

Installation Conditions

Installation Method

Direct buried — trefoil Direct buried — flat In duct — trefoil In duct — flat In air — trefoil In air — flat (touching) In air — flat (spaced) Tunnel / trough

Burial Depth to Cable Centre

1.0 m

0.5 m2.5 m

Soil Thermal Resistivity

0.7 K·m/W
Very moist 1.0 K·m/W
IEC ref 1.2 K·m/W
IS ref 1.5 K·m/W
Dry loam 2.0 K·m/W
Dry sand 2.5 K·m/W
Very dry 3.0 K·m/W
Dry slag

Ambient Ground Temperature

30 °C

10°C45°C

Cable Grouping

Screen / Sheath & Other Corrections

Screen Bonding

Single-point bonding Cross-bonding Solidly bonded both ends

Loss Angle (tan δ) — Insulation

0.001 — XLPE standard 0.002 — XLPE aged 0.004 — EPR

Load Factor (LF)

1.00

0.501.00

Additional Corrections

IS 3961 Indian conditionsReference: ρ = 1.2 K·m/W, T_g = 30°C, T_air = 40°C (instead of IEC defaults)

Partial drying-out of soilIEC 60287-2-1 §1.4 — additional correction for dry soil zone around cable

Duct filled with grout / sandEliminates air gap in duct — increases thermal resistance

Concrete encasementAdditional thermal barrier (IS 3961 Pt.5 correction)

Base Current Ratings — IEC 60287 / IS 3961

Single-core XLPE copper, direct buried trefoil, depth ≈ 0.8–1.0 m. IEC ref: ρ = 1.0 K·m/W, T_g = 20°C. IS 3961 ref: ρ = 1.2 K·m/W, T_g = 30°C. Highlighted row = currently selected size.

Size (mm²)	11 kV	33 kV	66 kV	132 kV	220 kV

Derating — Ambient Temperature

Ground Temp (°C)	10	15	20	25	30	35	40	45
DF (IS ref 30°C)	1.100	1.073	1.044	1.022	1.000	0.975	0.949	0.919
DF (IEC ref 20°C)	1.118	1.094	1.068	1.049	1.025	1.000	0.972	0.943
Air Temp (°C)	—	25	30	35	40	45	50	55
DF (IS ref 40°C)	—	1.100	1.069	1.035	1.000	0.962	0.921	0.875

Derating — Soil Thermal Resistivity

ρ (K·m/W)	0.7	1.0	1.2	1.5	2.0	2.5	3.0
DF (IEC ref 1.0)	1.195	1.000	0.913	0.816	0.707	0.632	0.577
DF (IS ref 1.2)	1.309	1.095	1.000	0.894	0.775	0.693	0.632

Derating — Cable Grouping (IEC 60287-2-1 Annex B)

No. of cables	Touching	0.25 m	0.30 m	0.50 m	0.75 m	1.0 m	1.5 m
1	1.000	1.000	1.000	1.000	1.000	1.000	1.000
2	0.820	0.850	0.870	0.900	0.930	0.960	0.980
3	0.750	0.780	0.810	0.850	0.890	0.930	0.960
4	0.700	0.730	0.760	0.800	0.850	0.890	0.930
6	0.630	0.660	0.700	0.750	0.800	0.840	0.890
9	0.570	0.600	0.630	0.690	0.740	0.780	0.840

Derating — Installation Method

Installation	Factor	Notes
Direct buried — trefoil	1.00	Reference condition
Direct buried — flat touching	0.97	Centre cable runs hotter
In duct — trefoil (air filled)	0.87	Duct adds thermal resistance
In duct — flat (air filled)	0.85
In duct — grouted	0.82	Grouting fills air gap
In air — trefoil (touching)	1.05	Convective cooling benefit
In air — flat (touching)	0.97
In air — flat (spaced ≥ D)	1.10	Full convection on all cables
In tunnel / trough	0.90	Depends on ventilation

Disclaimer: This tool provides preliminary estimates based on IEC 60287-1-1:2023 and IS 3961 (Parts 3 and 5). Actual project ratings must be determined by the cable manufacturer using detailed calculations with actual cable construction data. Not a substitute for professional engineering analysis.

Selecting a high-voltage cable is not simply a matter of choosing a larger conductor size. The cable must carry the required load current continuously without exceeding its permissible conductor temperature under the actual installation conditions. This cable rating calculator helps you determine that current carrying capacity quickly and accurately.

The calculator supports voltage levels from 11 kV to 220 kV and conductor sizes from 185 mm² to 1200 mm². You can select either copper or aluminum conductor and choose the applicable installation method. Site-specific parameters such as soil thermal resistivity, burial depth, ambient ground temperature, cable grouping arrangement, screen bonding method, duct installation, concrete encasement, and solar radiation can also be entered.

Based on these inputs, the calculator applies the relevant correction and derating factors in accordance with IEC 60287-1-1 and IS 3961 (Parts 3 and 5). It then calculates the derated continuous current carrying capacity of the cable in amperes along with the corresponding three-phase MVA capacity.

Each derating factor is displayed separately with its calculated value, colour-coded indication, and reference to the applicable standard clause. This allows you to identify the factors responsible for reducing the cable rating and understand their individual impact on the final current carrying capacity.

The Reference Tables section contains the base current ratings for various voltage levels and conductor sizes. It also includes standard derating factor tables for ambient temperature, soil thermal resistivity, cable grouping, installation method, and other commonly used correction factors. These tables are useful for verification and manual calculations.

The calculated results can be printed directly or copied as a plain-text report for documentation and engineering records.

Important: The results provided by this calculator are intended for preliminary design studies, cable selection, and feasibility assessment. Final cable ratings for detailed engineering, procurement, and construction should always be verified by the cable manufacturer using a complete IEC 60287 calculation based on the actual cable construction and installation parameters.