DC is not AC with a different label. Why the insulation system and the termination carry more risk than the conductor, what to specify on the cable itself, and when a pre-assembled harness beats loose cable.
On a solar plant the cable is the most-installed item and the least-considered one. A string that underperforms two years after commissioning is rarely a module problem — more often it is a termination or a connector pair that was specified on cross-section alone.
DC is not AC with a different label
The single technical fact that should shape a PV cable specification is that a DC arc does not self-extinguish the way an AC arc does. An alternating current crosses zero on every cycle, and that zero is what most AC protection relies on. A direct current has no such moment: once an arc is struck at a poor joint or a damaged conductor, it can persist.
Two consequences follow, and both are specification decisions rather than installation preferences:
- 1The insulation system carries more of the risk than the conductor. A single layer of insulation damaged by a pulled staple or a sharp racking edge exposes a conductor that is live whenever the array is illuminated. A double-insulated construction means one mechanical damage event does not by itself expose the conductor.
- 2Terminations and connector pairs deserve more attention than the run. The cable in the middle of a tray rarely fails. The failure concentrates where the conductor ends — at the crimp, the lug, and the mating pair.
What to specify on the cable itself
| Field | What it decides |
|---|---|
| System voltage | 1000 V or 1500 V systems take different cable constructions |
| Cross-section | 2.5, 4 or 6 mm² — set by current and volt drop, not by habit |
| Conductor | Tinned copper, for corrosion resistance at the termination |
| Insulation | Double-insulated (XLPO) construction, for outdoor exposure and mechanical damage |
| Run and environment | Tray, conduit, direct on racking — and the UV exposure that follows |
| Delivery form | Loose cable, or a finished assembly with connectors already fitted |
The last line is the one buyers most often leave until after the quotation. A harness that arrives as loose cable and loose connectors is assembled on site, in the weather, by whoever is available — and every hand-made joint is a place where the specification quietly stops being the specification.
Why the conductor is tinned
A copper conductor exposed to moisture and to the thermal cycling of a working array oxidises, and the oxide layer is a resistance at exactly the point where you least want one. Tinning protects the copper at the termination, which is where the conductor is stripped back and the metal is exposed to the environment.
It is a small material decision with a long consequence. Untinned copper in an outdoor DC run is not an immediate fault; it is a joint that gets warmer each year.
Assemblies: single-head, double-head, and IP67
The range covers PV extension-cable assemblies rather than only bulk cable, in three forms:
- Single-head assemblies, for extending one polarity of a string run.
- IP67 single-head versions, where the joint sits in a position exposed to water and dust — roof-mounted or ground-mounted racking rather than inside a combiner enclosure.
- Double-head assemblies, where both ends terminate in connectors — the form used when a run is made up entirely of pre-terminated sections.
The IP67 rating matters in the same way the double insulation does: it is a statement about what happens when the joint is where the weather is, rather than a marketing grade attached to a connector that will spend its life dry.
Grounding the array, not just the equipment
The grounding conductor holds the module frames, the mounting structure and the inverter enclosure at the same potential. It is specified by cross-section and by the environment it runs through — which is why the PVC-sheathed stranded copper range is quoted by section (2.5–10 mm² and 16–150 mm² versions are both in it) rather than as a single part number.
Two practical points come up repeatedly on PV projects:
- The bonding path has to be continuous between the frames. Mounting clamps with a painted or anodised interface do not necessarily make an electrical connection; the bond is a conductor, not a hope.
- Surge protection belongs on the AC side of the plant as well. Composite-insulated zinc oxide surge arresters are part of the range; tell us the system voltage and the installation conditions and the arrester is selected against them.
Compliance on a live DC array
A PV array generates whenever it is illuminated, so the DC side cannot be treated as dead just because the AC side is isolated. That changes the maintenance equipment list rather than the cable specification, but the two belong to the same project: proving the point of work dead, matting to work from, insulating gloves and footwear, and an insulating ladder or platform to reach the string boxes.
If you are assembling the whole plant rather than the DC side alone, the solar PV plant application page sets out the full equipment list for that worksite.
FAQ
What DC cable do you supply?
DC tinned-copper solar PV cable in 2.5, 4 and 6 mm² with double XLPO insulation, for 1000 V and 1500 V systems — see the PV cable range — together with PV extension-cable assemblies in single-head IP67 and double-head versions. Tell us the system voltage, the cross-section and the connector type.
Should I buy cable or pre-assembled harnesses?
If the runs are predictable and the site has limited access to good crimping tools, pre-assembled harnesses remove the largest error source on a PV installation: hand-made joints in the field. Both are available, and mixed orders are common.
How is the grounding conductor specified?
By cross-section and by the routing environment. The PVC-sheathed stranded copper grounding conductors are supplied in two sections — 2.5–10 mm² for bonding and smaller runs, and 16–150 mm² for array grounding runs. Tell us the section and where the conductor has to run.
Do you supply the lugs and terminations?
Yes — copper cable lugs including dual-hole types for bolted busbar and terminal connections, supplied to the conductor sizes on the order, together with insulated heat-shrink sleeving for the finished termination.
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The accessory line is quoted against the installation rather than from a stock list, and it sits alongside the safety equipment in the same manufacturing and export operation — so a mixed PV order travels as one shipment on one set of export documents. The accessories range is the starting point.
Need this confirmed against your own installation?
Send us the network voltage, the standard you are specifying against and the ambient conditions. Our engineers will confirm the class, thickness and test report, and reply with lead time.
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