Selecting the right cable cross-sectional area is a cornerstone of safe, efficient, and cost-effective electrical systems. Many engineers rely on experience or simplified rules, which may work in the short term but can lead to overheating, excessive voltage drop, or early insulation failure.

Shenghua Cable (Shanghai Shenghua Cable Technology Group Co., Ltd.), with decades of expertise in cable manufacturing and international projects, shares four scientific approaches to selecting cable cross-sections for diverse applications.

Explore Shenghua Cable’s products here:https://www.shanpowercable.com/

Cables are designed to carry a certain current without exceeding their long-term allowable temperature. Exceeding this temperature accelerates insulation aging and may reduce service life.

• PVC insulation: maximum 70°C

• XLPE insulation: maximum 90°C

Example:

• Transformer: 2500 kVA, 10 kV supply

• Cable type: XLPE, installed in cable bridge

Step 1: Calculate rated current

I=250010.5*1.732≈137AI = frac{2500}{10.5 times 1.732} approx 137AI=10.5*1.7322500​≈137A

Step 2: Check cable catalog

• YJV-8.7/10KV-3X25 → 120A

• YJV-8.7/10KV-3X35 → 140A

Step 3: Select cable

• YJV-8.7/10KV-3X35 meets 137A safely

Tip: Always consider environmental conditions and installation method when using this approach.

This method balances material cost and energy efficiency. Choosing too small a cable increases losses, while overly large cables increase investment unnecessarily.

Procedure:

1. Determine equipment rated current

2. Calculate annual operating hours

3. Look up economic current density (A/mm²) for those hours

4. Divide equipment current by economic density to determine cross-section

Example:

• Equipment current: 150A

• Operation: 8000 hours/year

• Economic density: 1.75 A/mm²

$S=1.75150\approx 85.7mm²$

Step 2: Choose nearest standard size → 95 mm²

This ensures cost-efficient cable sizing with minimal power loss.

Long cable runs can suffer significant voltage drop, affecting sensitive equipment performance and efficiency. Voltage drop limits are typically ≤7% for low-voltage systems (400V).

Voltage drop formula:

S=I⋅ρ⋅LΔUS = frac{I cdot rho cdot L}{Delta U}S=ΔUI⋅ρ⋅L​

• III = rated current

• ρrhoρ = conductor resistivity (Ω·mm²/m)

• LLL = cable length (m)

• ΔUDelta UΔU = allowable voltage drop

Example:

• Device voltage: 380V

• Rated current: 150A

• Cable length: 600 m

• Copper resistivity: 0.0175 Ω·mm²/m

• Allowable drop: 26.6V

S=150*0.0175*60026.6≈59.2 mm²S = frac{150 times 0.0175 times 600}{26.6} approx 59.2 text{ mm²}S=26.6150*0.0175*600​≈59.2 mm²

Step 2: Select nearest standard size → 70 mm²

This ensures stable voltage at the equipment end.

For high-voltage systems, cables must withstand the thermal effect of short-circuit currents without damaging insulation.

Formula:

$S\min =CIdti$

• IdI_dId​ = short-circuit current

• tit_iti​ = breaker operating time

• CCC = cable thermal coefficient (80)

Example:

• Short-circuit current: 18 kA

• Breaker time: 0.25 s

Smin⁡=18000*0.2580≈112.5 mm²S_{min} = frac{18000 times sqrt{0.25}}{80} approx 112.5 text{ mm²}Smin​=8018000*0.25​​≈112.5 mm²

Step 2: Select nearest standard size → 120 mm²

Even for low-rated devices, the cable must safely carry short-circuit currents.

Shenghua Cable provides:

• Precision-manufactured insulation for consistent dielectric strength

• Reinforced sheaths for mechanical and environmental protection

• Compliance with international certifications

• Technical guidance for project-specific cable sizing

These features ensure your electrical system is safe, efficient, and durable.

Visit our website for technical specifications and project support:https://www.shanpowercable.com/

Selecting cable cross-sectional area is a multi-dimensional decision. By considering:

1. Long-term current capacity

2. Economic current density

3. Voltage drop

4. Short-circuit thermal stability

Engineers can achieve optimal safety, efficiency, and cost-effectiveness.

Shenghua Cable combines high-quality materials with engineering expertise to provide reliable, long-lasting cable solutions for industrial, energy, and infrastructure projects worldwide.