Earthing Rod Size Calculator
Calculate earthing rod dimensions and cable sizing for grounding systems
Earthing Rod Size Calculator
Compliant with IEC 62305 & IEEE 80 Standards
Results:
Single Rod Resistance: 0.00 Ω
Number of Rods Required: 0
Cable Cross-Section: 0.00 mm²
Recommended Cable Size: 0 mm²
How to Use the Calculator
Soil Resistivity
- Measure soil resistivity on-site using Wenner method
- Enter value in Ohm-meters (Ω·m)
- Typical values: Clay 10-100, Sand 100-1000, Rock 1000-10000
- Use average of multiple measurements
Rod Specifications
- Enter rod length in meters (typically 2-4m)
- Specify rod diameter in millimeters
- Standard sizes: 12mm, 16mm, 20mm, 25mm
- Longer rods provide better grounding
Fault Parameters
- Enter maximum fault current from system analysis
- Specify protective device operating time
- Choose conductor material (copper recommended)
- Set target resistance (≤5Ω typical, ≤1Ω for sensitive equipment)
Earthing System Fundamentals
Resistance Calculation
Single rod resistance depends on:
- Soil resistivity (ρ)
- Rod length and diameter
- Installation depth
Cable Sizing
- Based on adiabatic principle
- Fault current magnitude and duration
- Conductor material properties
Key Formulas:
Single Rod: R = ρ/(2πL) × ln(4L/d)
Cable Size: A = I × √t / k
Where: ρ=soil resistivity, L=length, d=diameter, I=fault current, t=time, k=material constant
Calculation Formulas
Single Rod Resistance:
R = ρ/(2πL) × ln(4L/d)
Cable Cross-Section:
A = I × √t / k
Multiple Rods:
R_total ≈ R_single / n × efficiency_factor
Example Calculation
Earthing System Design:
Soil Resistivity: 150 Ω·m
Rod: 3m length, 16mm diameter
Fault Current: 20,000A, Duration: 0.5s
Single Rod R = 150/(2π×3) × ln(4×3/0.016) = 44.7Ω
Cable Size = 20,000 × √0.5 / 205 = 69 mm²
Result: 10 rods needed, 70mm² copper cable
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