Start with the markings

Genuine cable carries its identity printed along the sheath and on the drum label. Missing, inconsistent or smudged marking is the first warning sign.

  • BIS / ISI mark with a legible licence number
  • Manufacturer name and brand printed on the sheath
  • Nominal cross-sectional area and number of cores
  • Voltage grade and the standard the cable is made to
  • Batch or lot number, traceable to a test certificate
  • Sequential length marking along the sheath

Sequential length marking deserves particular attention. It is how you verify that a drum labelled 500 metres actually holds 500 metres.

Conductor resistance is the honest test

The most common form of cable fraud is a conductor slightly under its nominal cross-section — a 4 sq mm cable that is really 3.6 sq mm. Visually it is undetectable, and it fails by overheating under exactly the load it was bought for.

Conductor resistance per kilometre is the objective check. It is specified in IS 8130 for every size and conductor class, it is measurable, and it cannot be faked by appearance. A conductor below its nominal area will show resistance above the permitted maximum.

If you check one thing on a consignment, check conductor resistance against the IS 8130 limit for that size and class. It catches the defect that costs the most.

Insulation thickness and eccentricity

Standards specify both a nominal insulation thickness and a minimum at any point. A cable can meet its nominal average while having a thin spot where the conductor sits off-centre.

That thin section is where dielectric stress concentrates and where the cable will eventually fail. Check thickness at several points around the circumference on a cut sample, not just once.

Ask for the test certificate

Every reputable manufacturer issues routine test certificates covering conductor resistance and the high-voltage test for each production batch.

Request the certificate and confirm the batch number on it matches the batch number on the drum you are being supplied. A certificate for a different batch tells you nothing about the cable in front of you.

  • Routine test certificate covering the specific batch
  • Conductor resistance results against the standard limit
  • High-voltage test result
  • Batch number matching the drum label

Inspect the physical condition

Finally, look at the drum itself. Transport and storage damage is common and easy to miss during a rushed handover.

  • Sheath free of cuts, gouges, flattening and deep abrasion
  • No kinks or sharp bends from poor handling
  • Drum flanges intact and cable ends properly sealed against moisture ingress
  • Uniform sheath colour with no scorching or discolouration
  • Consistent outer diameter along the length

Unsealed cable ends matter more than they look. Moisture wicking into the conductor along the strands causes corrosion well beyond the exposed end, and the damage is not visible when you cut back.