Premium Membership ♕

CYBER WEEK OFFER 💥 Save 20% on PRO Membership Plan and Video Courses with the coupon CYM23 (Expires in 2 days).

Home / Technical Articles / Characteristics of XLPE insulated cables

Cross-linking effect

XLPE is the recognized abbreviation for cross-linked polyethylene. This and other cross-linked synthetic materials, of which EPR (ethylene propylene rubber) is a notable example, are being increasingly used as cable insulants for a wide range of voltages.

Characteristics of XLPE insulated cables with reference to the UK standards
Characteristics of XLPE insulated cables with reference to the UK standards (on photo: 10kV Aluminium Conductor XLPE Insulated Aerial Cable)

Polyethylene has good electrical properties and in particular a low dielectric loss factor, which gives it potential for use at much higher voltages than PVC. Polyethylene has been and still is used as a cable insulant, but, as a thermoplastic material, its applications are limited by thermal constraints.

Cross-linking is the effect produced in the vulcanization of rubber and for materials like XLPE the cross-linking process is often described as ‘vulcan- ization’ or ‘curing’. Small amounts of chemical additives to the polymer enable the molecular chains to be cross-linked into a lattice formation by appropriate treatment after extrusion.

The effect of the cross-linking is to inhibit the movement of molecules with respect to each other under the stimulation of heat and this gives the improved stability at elevated temperatures compared with the thermoplastic materials. This permits higher operating temperatures, both for normal loading and under short-circuit conditions, so that an XLPE cable has a higher current rating than its equivalent PVC counterpart.

The effects of ageing, accelerated by increased temperature, also have to be taken into account, but in this respect also XLPE has favourable characteristics.

BS 5467 specifies construction and requirements for XLPE and EPR-insulated wire-armoured cables for voltages up to 3.3kV. The construction is basically similar to that of PVC cables to BS 6346, except for the difference in insulant. Because of the increased toughness of XLPE the thicknesses of insulation are slightly reduced compared with PVC.

33kV XLPE cable
33kV XLPE cable (photo credit:

The standard also covers cables with HEPR (hard ethylene propylene rubber) insulation, but XLPE is the material most commonly used. From 3.8kV up to 33kV, XLPE and EPR insulated cables are covered by BS 6622 which specifies construction, dimensions and requirements.

The polymeric forms of cable insulation are more susceptible to electrical discharge than impregnated paper and at the higher voltages, where the electrical stresses are high enough to promote discharge, it is important to minimize gaseous spaces within the insulation or at its inner and outer surfaces.

To this end XLPE cables for 6.6 kV and above have semiconducting screens over the conductor and over each insulated core. The conductor screen is a thin layer extruded in the same operation as the insulation and cross-linked with it so that the two components are closely bonded. The screen over the core may be a similar extruded layer or a layer of semiconducting paint with a semiconducting tape applied over it.

Single-core and three-core designs are employed, and there is scope for constructional variation depending on the conditions of use, subject to the cores being surrounded individually or as a three-core assembly by a metallic layer, which may be an armour, sheath or copper wires or tapes.

A typical armoured construction which has been supplied in substantial quantities is shown in Figure 1 below.

XLPE cable construction
Figure 1 – XLPE cable construction


  1. Circular stranded conductor
  2. Semiconductor XLPE screen
  3. XLPE insulation
  4. Semiconducting tape screen
  5. Copper tape screen
  6. PVC filler
  7. Binder
  8. Extruded PVC sheath
  9. Galvanized steel wire armour 10. Extruded PVC oversheath

In the UK this type of cable, mainly in single-core form, is favoured for power station cabling, where lightness and convenience of terminating are major considerations. Three-core designs are also used for site supplies.

Underground direct buried power cables
Underground direct buried power cables

For underground distribution at 11kV, the XLPE cable does not compete economically with the paper-insulated aluminium-sheathed cable, but work is in progress on standardizing and assessing XLPE cable design, including trial installations, in preparation for any change in the situation. Overseas, where circumstances are different, XLPE cable is the type in major demand.

With manufacturing facilities increasingly orientated to this market, XLPE insulated cables constitute a large proportion of UK production.

Cold Shrink Cable Joint – XLPE Single Core High Voltage Cable

Reference: Newnes Electrical Pocket Book – E.A. Reeves DFH(Hons), CEng, MIEE Martin J. Heathcote BEng, CEng, FIEE

Premium Membership

Get access to premium HV/MV/LV technical articles, electrical engineering guides, research studies and much more! It helps you to shape up your technical skills in your everyday life as an electrical engineer.
More Information

Edvard Csanyi

Electrical engineer, programmer and founder of EEP. Highly specialized for design of LV/MV switchgears and LV high power busbar trunking (<6300A) in power substations, commercial buildings and industry facilities. Professional in AutoCAD programming.


  1. Paul Stefano
    Mar 17, 2022

    What is the minimum PVC bedding thickness for a three core 11kV LV cable?

    Mar 18, 2019

    When XLPF cable is used in place of old style oil filled for 138kV line are there significant changes in the radiation field? If so, are there any shielding suggestions?

  3. Ken Nwankwo
    Nov 27, 2018

    Can XLPE Cables suffer insulation failure due to extreme hot temperature?

  4. srinivas
    Nov 20, 2017

    i want to know about best technology/ practices in U.G HIGH VOLTAGE (33KV) CABLE LAYING /PULLING

  5. David C. Madumere
    May 10, 2017

    I will like to have your material on characteristics of XLPE cables.

  6. nazrol
    Mar 13, 2017

    what equipment can used to cutoff the xlpe cable.. because i only want xlpe insulation in that cable to perform breakdown test.. tq

    • Roxie Zhang
      Jan 22, 2019

      I’m Roxie from Hebei Fangyuan Instrument & Equipment Co.,Ltd,we produce cable test machine,XLPE cable insulation cutting machine,cable slicing and chipping machine,pls feel free to contat me.
      Email:[email protected]

  7. Md. Bakhtiar uddin
    Sep 12, 2015

    I am very much interested for manufacturing xlpe cables in my factory. Pl help me.

    • Roxie Zhang
      Jan 22, 2019

      I can help you.Pls contact me.
      Email:[email protected]

  8. Hussein
    Mar 02, 2015

    Please advice if the earth cable 150 connected between the MDB to SMB can be spliced .
    Thank for your prompt reply.

  9. mohammad adel
    Dec 26, 2014

    I am very interested in designing electrical substation

Leave a Comment

Tell us what you're thinking. We care about your opinion! Please keep in mind that comments are moderated and rel="nofollow" is in use. So, please do not use a spammy keyword or a domain as your name, or it will be deleted. Let's have a professional and meaningful conversation instead. Thanks for dropping by!

  +  17  =  eighteen

Learn How to Design Power Systems

Learn to design LV/MV/HV power systems through professional video courses. Lifetime access. Enjoy learning!

Subscribe to Weekly Newsletter

Subscribe to our Weekly Digest newsletter and receive free updates on new technical articles, video courses and guides (PDF).
EEP Academy Courses - A hand crafted cutting-edge electrical engineering knowledge