Cable Manufacturer Case Study: 1,500 V DC Solar Cable

A 60 MW solar park needed 96 km of DC cable that would survive 25 years of ultraviolet, heat and dust. The EPC's inspection regime would reject any string cable without a certified type approval. We supplied the cable manufacturer package in five deliveries. Batch tests passed at the first attempt, and only 0.2 per cent of joints needed re-termination.

Project Snapshot

The Problem: A Cable Spec That Has to Survive the Inspection

Solar parks are built in places with strong sun, high ambient temperature and abrasive dust. That is good for generation and hard on cable. The DC side is also unlike the AC side, because a string cable sits at a sustained direct voltage and carries the sun's heat all day.

This project had a further constraint that decided the order. The EPC's quality plan required a certified type approval for the string cable, and the site's insurance file required the same document. A cheaper uncertified cable would have been cheaper only until the inspection, at which point the choice would have been to cut it out or to argue about it.

Why We Chose a Certified Cable Manufacturer Over Local Assemblers

Three options were considered.

General purpose PVC insulated cable sized for the string current. Excluded. It is not rated for 1,500 V DC duty on the photovoltaic side, it has no ultraviolet rating for permanent outdoor exposure, and it would not have passed the inspection requirement.

Uncertified solar cable at a lower unit price. Excluded. The saving is real and the risk is larger. Certification is the document that closes the EPC's quality file, and without it the delivery date is at the mercy of an inspector.

One certified manufacturer for DC and AC. Selected. One specification, one certificate file, one marking convention, and a delivery schedule that we control end to end.

The Cable We Supplied

The core of the order was single-core solar cable for the DC side, built for 1,500 V DC with a cross-linked halogen-free insulation and sheath and a flexible tinned copper conductor. The tinned surface matters on a coastal or dusty site, because it resists the surface oxidation that raises resistance at a termination over time.

Sizing followed the site's real conditions rather than a table. We checked the conductor against ambient temperature, cable grouping and string current, then confirmed voltage drop over the longest run, which produced a mix of 4 mm² and 6 mm² strings.

For the AC side we supplied PVC insulated and sheathed cable for collection circuits, plus control cable for the tracker and inverter signals. The same plant also makes the higher-voltage power cable used on the grid side, which the EPC had ordered before on a substation upgrade covered in our 110 kV XLPE cable for substation upgrades case.

The approvals are the part that closes the file. Our solar cable is certified to IEC 62930, the international standard for cross-linked photovoltaic cables rated up to 1,500 V DC, and we hold CE, KEMA, EAC and GOST approvals, ISO 9001, ISO 14001 and ISO 45001 certification, and a CNAS accredited laboratory for our own testing. Cable comes off 21 factories across seven production bases, with a monthly capacity of 15,000,000 m.

Installation: How the Work Ran

Delivery was planned around the EPC's string installation sequence rather than around a container load.

The order went out in five deliveries over ten weeks, matched to the areas being strung. Each delivery carried a drum schedule with drum length, conductor size, batch reference and the corresponding test report, so the site could trace any drum back to its test data without calling us.

Two preparation steps came before the first drum. We agreed a drum length with the EPC's installers, because a drum that is too long leaves an offcut and one that is too short creates a joint on the string. And we agreed the cable marking convention with the site's commissioning team, so that a cable can be identified in a trench after backfilling.

Installation followed standard practice: pulled with a controlled tension winch, kept inside the minimum bend radius, and terminated with the right connector class.

Testing and Quality Control

Every batch is tested by us before dispatch, covering conductor resistance, a high-voltage withstand test, insulation resistance and dimensional checks, and the results travel with the drum schedule. On the trial batch the insulation resistance readings deviated from the reference by 0.4 per cent, and we held the batch until the extrusion parameters were rechecked.

Termination quality was monitored by the EPC's own audit. Only 0.2 per cent of joints needed re-termination, which is a low figure for a site of this size and a direct result of matching the connector to the conductor class.

Results: What the Numbers Show

All 96 km were delivered in five shipments, and every batch passed testing on the first attempt, so no delivery was held for retest. The string installation finished inside the programme, and the site's quality file closed without an exemption request.

The DC side has been in service since commissioning with no failed string tests on the cable itself. Terms are the ones we publish: 300 m minimum for power cable, 1,000 m for wire, 18 working days lead time.

What This Case Means for Your Project

On the DC side of a solar plant, the cable is not a commodity line item. Size the conductor for the real site temperature, insist on a certification document that matches the standard named in the specification, and plan drum lengths around the string layout.

We have been making cable since 1997 from a Shanghai head office, with more than 80 series in production and more than 600 engineers across the group. Send us your single-line diagram, routing and site conditions, and contact our team for a sized package with test documentation.