The Complete Guide To Medium Voltage Cables

Medium voltage cables typically refer to power cables with rated voltages ranging from 1 kV to 30 kV (or higher). These cables are used to connect high-voltage grids to low-voltage users, such as in substations, industrial power transmission, rail transit power supply, or large machinery power supply systems.

Applications of Medium Voltage Cables

Medium voltage cables play a crucial role in various industrial and municipal applications, including:

• Power Distribution Systems: Connecting high-voltage lines to low-voltage users in urban distribution networks.

• Large Factories and Major Power Users (e.g., hospitals, factories, airports).

• Rail Transit Power Supply Systems with voltage ratings typically ranging from 15–25 kV.

• Large Machinery and Mobile Equipment (such as cranes, conveyors) – highlighting flexibility and durability in mobile environments.

  
  

  
  

Medium voltage cable YJLV32

Structure of Medium Voltage Cables

The main components of medium voltage cables include:

1. Conductor: Typically made of copper or aluminum. Copper conductors are commonly used due to their high conductivity and durability.

2. Insulation Layer:

• XLPE (Cross-linked Polyethylene): High temperature resistance, chemical resistance, excellent dielectric properties.

• EPR (Ethylene Propylene Rubber): Elastic, ozone-resistant, and aging-resistant.

3. Metal Shielding Layer: To maintain electrical field balance and reduce electromagnetic interference, the cable typically uses a semiconductor layer + copper tape or aluminum foil shielding.

4. Sheath and Outer Protection:

• Inner sheath protects against moisture and chemical corrosion.

• Armoring (steel or aluminum tape) provides mechanical protection.

• Outer sheath (PVC, PE, LSZH) protects against UV radiation and environmental wear.

Performance Features and Design Requirements

• Voltage Rating: Typically 1–35 kV, with design specifications meeting the insulation strength required for corresponding voltage levels.

• Bending Radius: Flexible cables may have a bending radius only 10 times the cable’s diameter in mobile environments.

• Fire Resistance: Use of halogen-free, fire-retardant materials to minimize toxic gas emissions in case of fire.

• Partial Discharge Control: Cables must operate continuously under high voltage without partial discharges to avoid insulation breakdown.

• Service Life: High-quality medium voltage cables can last 25 to 35 years with proper maintenance.

Standards and Testing Specifications

• International and Regional Standards: These include IEC 60502‑2, AEIC CS‑6/CS‑8, ICEA S‑68, UL‑1072, NEMA, etc.

• Factory Testing Items: These include dielectric strength, partial discharge, insulation thickness, sheath strength, and bending tests.

Selection and Usage Recommendations

• Choose cables based on voltage rating, installation environment (e.g., underground, outdoor, mobile equipment), mechanical strength, and fire resistance standards.

• For high-density installation or mobile environments, XLPE shielded flexible cables are recommended.

• Ensure that cables meet local regulations (such as NEC, national electrical standards, ISO/IEC) and conduct professional testing and acceptance before installation.

Medium voltage cables consist of multiple layers, including conductors, insulation, shielding, sheathing, and armoring, designed to safely and reliably transmit electrical power in high-voltage environments. Their design must balance electrical performance with mechanical characteristics, ensuring stable long-term operation through rigorous standards and testing.

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