How to Choose Solar PV Cable for a Photovoltaic Project

What does a PV string cable have to withstand?

A PV string cable runs outdoors for long periods under DC voltage, sunlight and temperature cycling. Rooftops and solar farms expose it to UV, ozone, heat, cold, water and movement, and these conditions act together. A cable that meets only the electrical rating can still fail early if its sheath is not suited to the site.

Most decisions in this guide follow from one question: what is the hottest condition the cable will see, and for how long will it stay there? Answer that first, and the rest of the selection becomes a matter of matching ratings.

How do you size a PV string cable?

Size the conductor from the design current, and apply the multipliers, grouping and ambient temperature prescribed by the project rules. Long strings may need a larger conductor to control voltage drop and energy loss, because a larger conductor reduces voltage drop along the same route. The voltage drop check should be run on the full route length, not on a single panel.

Correction factors multiply: the tabulated current rating is multiplied by the ambient temperature factor, the grouping factor and any other factor that applies. For PV cable, take the current ratings and correction factors from the PV cable manufacturer's datasheet or the rating tables that accompany the cable standard, because they are based on the cable's own temperature limits rather than on general-purpose cable tables. The project's PV design rules set the ambient temperature and grouping for the real installation.

Current capacity in amperes depends on installation method and must come from the applicable tables or the manufacturer. The ampacity and derating guide explains how the correction factors are applied.

What do the PV cable ratings mean?

IEC 62930 and EN 50618 set the core ratings for cable used with photovoltaic systems. The table below summarises the values these standards give for a typical PV cable such as H1Z2Z2-K, with the check to make for each one. Each value is a basis for comparison, so the product datasheet for your exact product code still governs.

Values are summarised from IEC 62930 and EN 50618 as cited in manufacturer datasheets. Check the current edition of the standard and the product datasheet before you rely on them.

Which standard should you specify on the order?

IEC 62930 is the international reference for electric cables used with photovoltaic systems, and EN 50618 is cited for the same kind of cable. Specify the standard by name on the purchase order, together with the product designation such as H1Z2Z2-K. Projects may also require other regional standards or approvals, so confirm these before comparing prices.

Confirm conductor, insulation, sheath, temperature and voltage ratings together. A cable can meet one requirement and still fall short on another, and a supplier answer that covers only one of them is not enough to confirm the product.

How do connectors and crimping affect the circuit?

Use compatible connectors, approved tools and a documented crimping procedure. Mixing connector families or poor crimping can create high-resistance joints, and such joints can overheat even when the cable itself is correctly sized. Increasing the conductor size does not fix a poor joint.

• Confirm that the connector is listed as compatible with the cable you are buying.
• Avoid mixed connector families unless the design explicitly approves them.
• Require the crimp tool and procedure named by the connector maker, and keep a record of them.

How should PV cable be routed and supported?

Support the cable away from sharp edges and standing water. Avoid loose loops that rub on roofing or lie on the ground, because movement and abrasion add stress to the sheath and to the connector exits. Choose a sheath and armour that suit UV and weather exposure at the site, and state this exposure to the supplier when you order.

The minimum bending radius depends on the cable construction and the edition of the standard, and published values do not agree. Take the figure from the manufacturer's datasheet and apply it at every bend, including the bends at the connectors. PV circuit design and installation must follow the applicable local electrical and fire rules.

Frequently asked questions