BS 6622 covers armoured XLPE insulated cables for medium voltage distribution, with 6.35/11 kV being the common UK rating. Cross-linked polyethylene insulation sits between semiconducting conductor and insulation screens, with a metallic screen to carry earth fault current, galvanised steel wire armour and a PVC or LSZH oversheath. XLPE allows a 90°C conductor temperature, so it carries more current than the paper insulated cable it replaced and needs no maintenance of insulating fluid.
Key applications
- 11 kV primary and secondary distribution circuits
- Supplies between substations on industrial and commercial sites
- Wind farm, solar farm and generation connection circuits
- Grid connections for data centres and large developments
- Direct buried and ducted MV circuits
- Replacement and reinforcement of existing PILC networks
Features and benefits
- 90°C conductor rating gives higher current capacity than paper insulated cable
- Dry construction with no impregnant, so no fluid migration on vertical runs
- Simpler and faster to joint and terminate than PILC
- Steel wire armour suits direct burial and gives an earth fault path
- LSZH oversheath available where smoke and halogen emission matter
Specification notes and limitations
This is a medium voltage cable and must only be jointed, terminated and tested by competent HV personnel working to the manufacturer's accessory instructions — cold-strippable insulation screens, stress control and screen earthing all have to be executed correctly or the cable will fail in service. Minimum bending radius is twelve times the overall diameter, and MV cable cannot be pulled around corners the way LV cable is; drum handling, pulling tension and sidewall pressure all need calculating. Single core cables must use aluminium wire armour, not steel, to avoid eddy current heating, and screen bonding arrangements affect both rating and touch voltage. Current ratings depend heavily on soil thermal resistivity, depth, grouping and duct installation, so the published air rating is rarely the one that applies.
