XLPE Cable vs PVC Cable

What changes with the insulation temperature rating?

Cross-linked polyethylene (XLPE) has strong dielectric properties and commonly supports a higher normal conductor temperature than standard PVC insulation. The commonly cited limits are 90 °C in normal operation for XLPE and 70 °C for PVC. Under short circuit, for up to 5 s, the cited limits are 250 °C for XLPE and 160 °C for PVC. These values come from IEC 60502-1 as commonly cited and from manufacturer data, so check the datasheet of the cable you are buying.

A higher rating can help ampacity, but correction factors and installation conditions still apply. The reference ambient for cables in air is 30 °C. At 40 °C ambient in air, the correction factor is 0.87 for PVC and 0.91 for XLPE (IEC 60364-5-52, Table B.52.14). Correction factors multiply together. The grouping factor depends on the installation method in IEC 60364-5-52, so take it from the standard tables or the manufacturer rather than from a general rule.

PVC is robust, economical and easy to process. Different PVC compounds are available, so a generic name such as PVC does not establish a particular temperature or fire property.

Values are for comparison only. Confirm each one in the datasheet of the cable you buy, because the cited figures depend on the cable construction and the edition of the standard.

How does the temperature limit affect short-circuit sizing?

The short-circuit temperature limit enters the adiabatic check as the k factor in S = I × √t / k, where S is in mm², I is in A and t is in s. The check is valid for faults up to about 5 s. For copper, k is 115 for PVC and 143 for XLPE. For fast fuses or circuit breakers, use the let-through I²t from the manufacturer instead. More detail is in the short-circuit rating guide.

As a worked example, a fault of 10,000 A cleared in 0.4 s on copper with PVC insulation gives S = 10,000 × √0.4 / 115, or about 55 mm². The next standard size is 70 mm². The same fault on copper with XLPE insulation gives a smaller required area, because k is 143 instead of 115.

Does the insulation decide the outer sheath and mechanical protection?

XLPE is not automatically the outer sheath. Many XLPE-insulated cables use a PVC, polyethylene (PE) or LSZH sheath. The sheath is the first line of defence against moisture, sunlight, oil and abrasion, so insulation and sheath should be specified as separate layers. Compare the XLPE insulated power cable and PVC insulated power cable constructions on the same basis.

Minimum bending radius, low-temperature handling and installation pulling limits should be taken from the manufacturer's data. They depend on the full construction and should not be assumed from the insulation material.

Which fire properties come from the compound and the tests?

Ordinary PVC contains halogens and may generate corrosive smoke during a fire. LSZH (low smoke, zero halogen) compounds are selected when smoke and acid-gas limits matter. Flame retardancy and circuit integrity need separate tests, and they must not be inferred from the word XLPE. Ask the supplier which test standards its offer claims.

The tests usually cited for these claims include:

• IEC 60332-1-2: flame test on a single vertical cable.
• IEC 60754-1: halogen acid gas content, where 0.5 % is a common LSZH acceptance value.
• IEC 61034-2: smoke density by light transmittance, where 60 % minimum is commonly used to classify low smoke. Some sectors, such as rolling stock, require more.

How should two offers be compared fairly?

Compare only offers that describe the same cable construction and test standard. Material comparisons are meaningful only when these items match:

• Same voltage and conductor class
• Same conductor cross-section and material
• Same insulation and sheath thickness
• Same flame, smoke and halogen tests
• Same armour, screen and water-blocking construction
• Same standard and test documentation

A common error is comparing an XLPE-insulated armoured cable with an unarmoured PVC cable and attributing the whole price difference to the insulation. Armour, sheath, screen and test scope can each change the price, so normalize them before judging the material choice.

Frequently asked questions