Solar PV cable operates in conditions that would destroy general-purpose building wire within a few seasons: continuous UV exposure, surface temperatures well above ambient, and a design life expected to match the array itself.
Why general-purpose cable fails on an array
Standard PVC building wire is rated 70 °C conductor temperature and has no meaningful UV stabilisation. Mounted on a rooftop rail in direct sun, the jacket chalks, then cracks, and the insulation resistance falls. The failure is gradual, which is why it often shows up as declining string performance rather than an outright fault.
What the PV-specific construction adds
Cross-linked insulation and jacket
PV cable uses cross-linked polyolefin rated 90 °C continuous with a 120 °C maximum conductor temperature and a 25-year design life under EN 50618. Cross-linking is what prevents softening at the temperatures a roof-mounted cable actually reaches.
Tinned copper conductor
The conductor is tinned to resist corrosion at terminations and connectors, which are the points most exposed to moisture ingress over a two-decade service life.
Double insulation
PV cable is double-insulated so that a single insulation failure does not create an earth fault - relevant because array wiring is often within reach on rooftops.
Sizing for voltage drop across a string
DC string runs are frequently long, and losses accumulate over the plant's life rather than showing up as a fault. Most designs target under 1 % drop on the DC side, which usually means sizing above the ampacity minimum.
What to verify before a shipment ships
Ask for the EN 50618 test report, the TUV certificate where the project requires it, and confirmation that the conductor is tinned to the stated class. These three items are checkable against the batch and are what an inspector will look for.
