What cross-linking changes
PVC is thermoplastic — heat it enough and it softens and eventually flows. Cross-linked polyethylene has its polymer chains chemically bonded into a three-dimensional network, which makes it a thermoset. It will not melt and re-flow; it holds its form right up to its temperature limit.
That stability is what permits a higher continuous operating temperature, and the higher temperature is what permits a higher current.
| Property | PVC | XLPE |
|---|---|---|
| Material type | Thermoplastic | Thermoset |
| Continuous conductor temperature | 70°C | 90°C |
| Short-circuit temperature | 160°C | 250°C |
| Current rating, same size | Reference | Higher |
| Dielectric loss | Higher | Lower |
| Voltage range | Low voltage | Low voltage through EHV |
Higher rating from the same copper
Because the conductor is permitted to reach 90°C rather than 70°C, an XLPE cable carries meaningfully more current than a PVC cable of identical cross-section under the same installation conditions.
On a large feeder that can be the difference between one size and the next, and the saving in conductor material often outweighs the higher cost per metre of the insulation.
Fault performance
The gap widens under fault conditions. XLPE tolerates 250°C for the short duration of a fault against 160°C for PVC, which gives it a more favourable constant in the adiabatic short-circuit calculation.
On systems with high prospective fault current, this is frequently what allows a smaller conductor to satisfy the short-circuit check.
Where PVC still makes sense
PVC has not been displaced everywhere, and specifying XLPE by reflex is its own kind of mistake.
- Lower material cost on cost-sensitive low-voltage work
- Greater flexibility, which eases routing in tight spaces
- Inherent flame resistance from its chlorine content
- Entirely adequate where thermal or voltage duty is modest
The trade-off is the chlorine that gives PVC its flame resistance also produces acid gas when it burns — which is exactly why fire-safety grades exist.
Choosing between them
Use XLPE where thermal duty, fault level or voltage grade demand it: medium and high voltage distribution, heavily loaded feeders, high ambient temperatures and buried runs where moisture resistance matters. Use PVC for modest low-voltage circuits where its rating is comfortably sufficient.
XLPE power cables are covered by IS 7098 (Part 1 up to 1.1 kV, Part 2 for 3.3–33 kV) and PVC insulated cables by IS 1554. Confirm the voltage grade and construction against the manufacturer data sheet.