MV Cable
An MV Cable (Medium-Voltage Cable) is an electrical cable designed to carry voltages typically between 1 kV and 33 kV, most commonly used in commercial, industrial, and utility-scale solar PV systems. In solar projects, MV cables form the critical link between inverters, transformers, switchgear, and the grid interconnection point, enabling safe and efficient transmission of generated power over long distances.
MV cables are engineered with enhanced insulation, mechanical protection, and thermal ratings to support high load currents and outdoor conditions. They play an essential role in ensuring system reliability, grid compliance, and long-term performance of solar plants.
Key Takeaways
- MV cables carry medium-voltage AC power from solar plants to substations or the grid.
- Essential for commercial and utility-scale PV systems.
- XLPE and EPR are the most widely used insulation materials.
- Proper sizing ensures system efficiency and safety.
- Long-term reliability heavily depends on installation quality.
What It Is
An MV cable is a robust, insulated power cable used to transport electricity at medium voltages. Unlike DC home-run conductors or LV AC wiring, MV cables handle the post-inverter AC output once a transformer steps the voltage up for transmission.
Within the broader design workflow, MV cable routing and sizing often align with processes like Solar Layout Optimization and Stringing & Electrical Design.
How It Works
1. Voltage Step-Up
After AC power is produced by the inverters, a transformer boosts it to 11 kV, 22 kV, or 33 kV depending on grid requirements.
2. Power Transmission
The MV cable then carries this medium-voltage AC energy across:
- Array blocks
- Collection points
- Substations
- Utility interconnection nodes
3. Insulation & Shielding Layers
Typical construction includes:
- Copper or aluminum conductor
- XLPE or EPR insulation
- Metallic screen or tape
- Optional armor for burial
- Outer protective jacket
4. Grounding & Fault Management
The metallic screen ensures safe fault-current dissipation and reduces electromagnetic interference.
5. Environmental Protection
MV cables are designed to withstand:
- UV exposure
- Soil chemicals
- Moisture
- Thermal cycling
Types / Variants
By Conductor Material
Copper MV Cables — higher conductivity, ideal for long runs or critical circuits
Aluminum MV Cables — cost-effective, widely used in large solar farms
By Insulation
XLPE — high thermal resistance, standard in modern solar plants
EPR — flexible, moisture-resistant
By Construction
Unarmored — used in conduits or duct banks
Armored (SWA/AWA) — ideal for direct burial and high-stress environments
How It’s Measured
Key Specifications
- Voltage Rating: 1–33 kV
- Conductor Size: 35–630 mm²
- Insulation Type: XLPE or EPR
- Current Capacity: Based on installation and ambient temperature
- Short-Circuit Rating: Measured in kA for 1–3 seconds
Common Formula
Voltage Drop:
ΔV = √3 × I × (Rcosφ + Xsinφ) × L
Practical Guidance
For Solar Designers
- Size cables considering ampacity, voltage drop, soil thermal resistivity
- Validate designs through Stringing & Electrical Design
- Update BOMs using Bill of Materials (BOM)
For EPCs
- Use XLPE armored cables for solar farms
- Maintain proper bending radius
- Conduct soil resistivity and trench-depth assessments
For Installers
- Use certified joints and terminations
- Ground cables properly before handling
- Perform partial discharge testing after installation
For Developers
- Integrate MV routing early within AHJ Compliance and permitting
- Coordinate with utility interconnection requirements
Real-World Examples
Residential
Some gated communities or estates with centralized transformers may use short MV runs for shared solar infrastructure.
Commercial (1–5 MW)
A shopping complex rooftop system steps up output to 11 kV, sending it through a 185 mm² XLPE MV cable to the interconnection kiosk 400 meters away.
Utility-Scale (50–300 MW)
A solar farm uses multiple 33 kV MV loops connecting inverter transformers to a substation via 240–630 mm² armored aluminum cables.
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