Cable Capacitance Calculator

Accurate capacitance calculations for single core and multi-core cables

Cable Capacitance Calculator

Compliant with IEC Standards for Cable Design

Results:

Capacitance: 0.00 μF/km

Capacitance per meter: 0.00 nF/m

Capacitive Reactance (50Hz): 0.00 Ω·km

Capacitive Reactance (60Hz): 0.00 Ω·km

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How to Use the Calculator

Single Core Cable

  1. Select "Single Core Cable"
  2. Choose insulation material
  3. Enter conductor diameter (d)
  4. Enter diameter over insulation (D)
  5. Verify relative permittivity

Multi-Core Cable

  1. Select "Multi-Core Cable"
  2. Choose insulation material
  3. Enter individual conductor diameter
  4. Enter diameter over core insulation
  5. Results show per-core capacitance

Material Selection

  1. PVC: Most common, higher capacitance
  2. XLPE: Lower capacitance, better performance
  3. Butyl/Silicone: Specialized applications
  4. Temperature affects permittivity

Cable Capacitance Fundamentals

What is Capacitance?

Capacitance is the ability of cable to store electrical charge. It is defined as ratio of electrical charge (Q) to electrical potential (V).

Formula: Q = C × V (Coulombs/Volt)

  • Measured in microfarads per kilometer (μF/km)
  • Depends on cable geometry and insulation material
  • Affects cable charging current and power losses

Cable Construction Impact

  • Single core cables with earthed metallic layer
  • 3-core cables with individual core screening
  • Electrostatic field contained within earth screen
  • Substantially radial field distribution

Key Points:

• Relative permittivity depends on temperature and frequency

• Describes characteristics of insulation material

• Power losses can be reduced by compacting conductors

• Mutual capacitance is reduced by conductor compacting

Calculation Formulas

Single Core Cable Capacitance:
C = εr / (18 × log(D/d)) μF/km

Where:
D = Diameter over Insulation (mm)
d = Diameter of Conductor (mm)
εr = Relative permittivity of dielectric

Capacitive Reactance:
Xc = 1 / (2π × f × C) Ω·km

Example Calculation

Single Core XLPE Cable:

Conductor diameter (d): 20mm

Insulation diameter (D): 35mm

XLPE permittivity (εr): 2.3

C = 2.3 / (18 × log(35/20))

C = 2.3 / (18 × 0.243) = 0.525 μF/km

Xc(50Hz) = 1/(2π × 50 × 0.525×10⁻⁶) = 6063 Ω·km

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