What Is the Underground Cable Capacitive Charging Current Calculator?
AC cables act as giant coaxial capacitors continuously drawing leading reactive charging current from the grid even under no-load conditions.
How Does the Underground Cable Capacitive Charging Current Calculator Work?
Calculates coaxial capacitance between inner conductor and outer metallic ground shield, then multiplies by system angular frequency and phase voltage.
Underground Cable Capacitive Charging Current Calculator Formula & Variables
The core mathematical equation utilized by this calculator is expressed as:
C = rac{2 pi arepsilon_0 arepsilon_r}{ln(R / r)} quad [ ext{F/m}], quad I_c = omega C V_{ ext{phase}}, quad Q_c = 3 V_{ ext{phase}} I_c
Coaxial cable electrostatic capacitance and steady-state AC charging reactive power generation.
How to Use the Underground Cable Capacitive Charging Current Calculator
- Input system voltage in kV, cable route length in km, conductor core radius in mm, and insulation wall thickness.
Step-by-Step Example Calculation
132 kV Offshore Wind Submarine Export Cable
Input Values:
lineVoltageKv:132
cableLengthKm:25
conductorRadiusMm:14
insulationThicknessMm:16
relativePermittivityEpsR:2.85
Worked Steps: Capacitance = 0.208 µF/km, Charging current = 37.4 A, Reactive power Qc = 8.55 Mvar.
Understanding Your Result
Displays continuous charging current in Amperes, total 3-phase reactive generation in Mvar, and capacitance per kilometer.
Factors That Affect the Result
- For long AC submarine cables (>50 km), charging current consumes a large fraction of conductor thermal current ampacity, requiring shunt reactors.
When Should You Use This Calculator?
- Offshore wind export cable sizing, grid interconnect studies, and shunt reactor compensation sizing.
Assumptions & Limitations
- Applies to single-core shielded coaxial power cables at steady-state power frequency (50/60 Hz).
Frequently Asked Questions
Calculation Accuracy & Reference Note
Standard IEC 60287 cable capacitance model.