Choosing the Right Cabling: DC vs AC Solar Cables

In a utility-scale or rooftop solar photovoltaic (PV) installation, cables act as the primary arteries of the system. They transport electrical energy from the solar panels, through the inverters, and ultimately to the electrical grid. A common design decision for solar installers is selecting the proper specifications for DC (Direct Current) and AC (Alternating Current) cabling. Selecting the wrong cable class or size is a leading cause of performance degradation, excessive voltage drop, and fire hazards.

Direct Current (DC) Solar Cables: Panels to Inverter

DC cables connect the individual PV modules in strings and run to the combiner boxes or string inverters. These cables operate in harsh outdoor conditions, exposed directly to sunlight, high heat, wind, and rain. Therefore, specialized solar DC cables (typically meeting standard EN 50618 / H1Z2Z2-K) are required.

• Double Insulation: Solar DC cables feature dual-wall cross-linked polyethylene (XLPE) or electron-beam cross-linked compounds to resist high electrical stress and physical abrasion.
• UV and Ozone Resistance: Outdoor wiring must endure continuous ultraviolet exposure without cracking or degrading over a 25-year service life.
• Tinned Copper Conductors: Unlike standard power cables, solar DC cables use finely stranded tinned copper. This provides maximum flexibility and protects the conductor against corrosion in damp environments.

Alternating Current (AC) Solar Cables: Inverter to Grid

Once the direct current is converted by the inverter, AC cables transport the energy to the main AC distribution board (ACDB) and onto the grid transformer. These cables are typically routed indoors, in trenches, or inside electrical conduits.

For AC cables, structural robustness and voltage drop mitigation are the primary criteria:

• Armouring: For underground runs, Steel Wire Armoured (SWA) or Aluminium Wire Armoured (AWA) AC cables are utilized to prevent mechanical damage from soil settlement or rodent activity.
• Conductor Material: While copper is superior in conductivity, heavy-duty AC runs often utilize aluminium conductors due to lower weight and significantly lower material costs for long-distance runs.

Mitigating Voltage Drop for Maximum Efficiency

Every volt lost in cables is a permanent reduction in energy yield and system ROI. Systems should be designed to maintain a voltage drop of under 1% on the DC side and under 2% on the AC side. Installers can achieve this by calculating the minimum cross-sectional area (e.g., 4 sq mm vs 6 sq mm for DC cables) based on current loads and run lengths. At Turvotek, we distribute premium Polycab solar cables specifically designed to maintain low internal resistance and minimize thermal losses under peak load conditions.