Cable quality control: routine, sample and type tests

Three levels of testing

Cable standards such as IEC 60502-1 and IEC 60502-2 split testing into three levels. Knowing which is which stops you accepting a type test report as proof of the drums you are buying, or paying for type tests you do not need.

The desk writes the routine and sample tests into the spec sheet, with acceptance values, and asks for the type test report that matches the exact construction, sheath compound and size range.

Conductor resistance: the first check

Conductor DC resistance at 20 C is cheap to measure and hard to fake across many drums. IEC 60228 sets the maximum: for copper Class 2, 2.5 mm2 is 7.41 ohm/km, 25 mm2 is 0.727, 50 mm2 is 0.387 and 95 mm2 is 0.193; for aluminium Class 2, 95 mm2 is 0.320 ohm/km. A conductor that sits above the limit usually has less metal than its nominal size. The desk compares every drum record with the limit, watches for identical figures repeated across drums, and re-measures cut samples when something looks wrong. See conductor resistance testing.

The undersized cable warning

BASEC has warned the market about SWA cable whose effective conductor size was up to two sizes smaller than marked, with both conductor and armour resistance out of limits. Such cable looks right from the outside and carries correct print. Two points follow. First, only cable printed with the BASEC name is BASEC-approved product; a BASEC approval held by one plant for one construction does not transfer. Second, resistance and armour checks per drum are the practical defence, not the brochure. The same logic applies to CCA sold as copper network cable: it is about 30% lighter, shows aluminium colour when scraped and can be identified by XRF, and category cable requires solid copper conductors. More in undersized conductor risk and cable problems guide.

Coils and boxes: AQL sampling

Drums are checked one by one. Building wire coils, flexible cord coils and 305 m boxes of LAN cable ship in thousands, so the desk inspects them by sampling to ISO 2859-1. The inspection level and AQL for critical, major and minor defects are agreed before production and written into the order.

• Critical: wrong conductor material, conductor resistance above the IEC 60228 limit, failed voltage test.
• Major: short length, wrong print text, insulation below the minimum thickness, wrong colour.
• Minor: label placement, carton scuffs, coil wrapping.

A lot that fails the plan is held for re-inspection or sorting at the plant, not shipped with a discount.

What a usable test record shows

A routine test sheet the desk accepts carries the drum number, construction and size exactly as printed on the sheath, production date, measured length, conductor resistance corrected to 20 C for each core, the test voltage and duration, the result, the instrument and its calibration date, and the name of the tester. For MV cable it adds the partial discharge level at the specified test voltage. Sheets without drum numbers, with resistance quoted as a single figure for all cores, or without instrument details are sent back before inspection, because they cannot be traced to the drum in front of you.

Fibre and data cable

For fibre cable, each drum carries OTDR attenuation and length data, reported against the fibre datasheet and, for G.652.D, the cabled fibre limits in the G.652 tables. Patch cords carry insertion and return loss per connector against IEC 61753-1 grades. For LAN cable, the desk asks for test results on samples from the batch and conductor material checks; installed channel or permanent link testing remains the installer's step.

How the desk runs quality control

1. The spec sheet lists routine and sample tests, acceptance values and the type report reference.
2. Routine records are collected per drum as production runs, not at the end.
3. Anomalies trigger re-measurement on cut samples or a witness test.
4. Final checks happen at pre-shipment inspection; start with the quote form.