Audit the construction, not the brochure
Most cable plants in the main Chinese clusters make a wide range of products. Yixing in Jiangsu reported wire and cable output above 100 billion yuan by the end of 2020 (Jiangsu provincial news, 2021), and the Ningjin cluster in Hebei counted 2,393 enterprises in 2024 (Hebei industry department, 2025). In clusters that size, almost every plant can show you an extrusion line. The question an audit has to answer is narrower: can this plant make and test your construction, at your standard, in your quantity, and prove it drum by drum?
So the desk starts every audit from the spec sheet. A plant that makes good 0.6/1 kV XLPE power cable to IEC 60502-1 may have no partial discharge room for medium voltage, no steel wire armouring line for BS 5467, or no route to an EN 50618 certificate for solar cable. The partner catalogue behind our medium-voltage page, for example, stops at 8.7/15 kV; higher classes are matched to a different plant. Writing the construction down first keeps the audit honest. The factory audit page explains how the desk scopes this before a visit.
One more question belongs at the start: which steps happen in this plant and which are bought in. Some plants draw their own wire; others buy drawn and stranded conductor. Some compound their own PVC; most buy compounds. Outsourcing is normal, but each bought-in step needs its own incoming inspection record, and an audit that only covers the final extrusion hall misses where many conductor and compound problems begin. Ask for the list of key suppliers and the incoming checks applied to each, and note any step that is subcontracted to another site, because that site is effectively part of your supply chain too.
Lines: what to walk through
Walk the process in the order the cable is made and ask to see your type of product running, or at least the last batch records for it.
| Area | What to check | Why it matters |
|---|---|---|
| Rod and wire drawing | Copper or aluminium rod source, purchase records, annealing | Conductor resistance starts here; recycled or mixed metal shows up later as failed resistance |
| Stranding | Strand count and wire diameter set-up sheets per size | Fewer or thinner wires is the usual route to an undersized conductor |
| Insulation extrusion | Compound type and lot records, thickness checks, spark tester on line | Thickness and compound quality drive voltage withstand and ageing |
| MV insulation lines | Conductor screen, XLPE and insulation screen applied in one controlled process, clean compound handling | Contamination and voids cause partial discharge |
| Laying up and armouring | Fillers, binder tape, steel tape or steel wire armour machines | STA is common; SWA and AWA need specialised plants |
| Sheathing and printing | Sheath compound, printer set-up, metre marking | Print is the buyer's first identification of the product |
| Drum yard | Drum types, lagging, end caps, covered storage | Damage in storage voids good test results |
For fibre cable, the equivalent walk is fibre colouring, loose tube or tight buffer lines, stranding, armour or strength members and sheathing, with the fibre source and spool records checked first. Fibre and cable plants concentrate in Wuhan's Optics Valley and Qidu in Wujiang; see the industry clusters page for which cluster suits which line.
Lab: equipment and how it is used
A lab corner with instruments is not the same as a test regime. Ask what is tested on every drum, what on samples, and what is covered by external type test reports, then check that the equipment matches.
- Conductor resistance: a resistance bridge with temperature correction to 20 C, and the operator able to show results against the IEC 60228 maximum for the size.
- Voltage test: a high-voltage set sized for the cable; for medium voltage the IEC 60502-2 routine test is 3.5 U0 for 5 minutes.
- Partial discharge: a screened room and a calibrated system for MV cable, measured to IEC 60885-3, with routine sensitivity of 10 pC or better at 1.73 U0.
- Dimensions: tools to measure insulation and sheath thickness and overall diameter on cut samples.
- Ageing and fire: ovens for thermal ageing, and either in-house flame test rigs or current external reports for IEC 60332-1-2 and other fire tests.
- Fibre: an OTDR for attenuation and length per fibre, and insertion and return loss sets for patch cords.
Ask for calibration certificates for the main instruments and check the dates. An uncalibrated resistance bridge makes every report it produces doubtful.
Records: the part most audits skip
Records are where good plants separate themselves. Pick a recent order of a similar construction and trace it backwards: drum number on the label, test record for that drum, production batch, compound lots and rod purchase. If the chain breaks, the reports you receive for your order will be just as hard to trust.
- Pull three drum numbers from the yard and ask for their test records on the spot.
- Check the resistance values against IEC 60228 for the size, not against the plant's own internal target.
- Compare the recorded insulation and sheath thickness with the datasheet values the plant quotes.
- Ask how failed drums are recorded, quarantined and scrapped or downgraded.
- Check who signs the release and whether they are independent of production.
Certificates and scope
Certificates belong to the plant and to a specific construction and model range, not to a company in general. A UL listing, a TUV certificate for EN 50618 solar cable or a BASEC approval for a BS construction is checked in the certifier's public database per order, against the plant name, the address of manufacture and the exact cable type. For the EU, a cable within EN 50575 needs a Declaration of Performance with the CPR class; the CE mark is a declaration, not a certificate. Our post on verifying cable certificates walks through the database checks.
Turning the audit into an order
An audit ends with a short list of findings and a decision: approved for this construction, approved with conditions, or not suitable. Conditions usually become order terms, such as witnessed routine tests, sample tests on the first drums or a pre-shipment inspection before the balance payment. MOQ and lead time for the approved plant are then confirmed in writing for each order; typical ranges are on the MOQ and lead time page. When you have a construction ready, send it through the quote form and the desk will scope the audit around it.