Cable and component terms, explained

XLPE

Cross-linked polyethylene. An insulation material used on power cables, chosen for its thermal, mechanical and electrical performance compared with standard PVC or PE insulation.

LSZH

Low Smoke Zero Halogen. A sheathing material that emits little smoke and no halogen acid gases when burnt, specified for tunnels, stations and other enclosed spaces where fire safety is critical.

SWA / AWA

Steel Wire Armour / Aluminium Wire Armour. A layer of helically wound wires under the outer sheath that gives a cable mechanical protection and, depending on design, can also carry earth fault current.

Screen

A conductive layer, usually copper tape or wire, applied over the insulation or cable core. It controls the electric field on MV/HV cables and provides electromagnetic shielding and a fault-current path on screened cables.

U0/U (Um)

The voltage designation used to rate power cables. U0 is the rated voltage between conductor and earth, U is the rated voltage between conductors, and Um is the maximum system voltage the cable can operate at — for example 6/10(12) kV.

OPGW

Optical Ground Wire. An overhead earth wire strung on transmission towers with optical fibres built into its core, combining lightning protection for the line with a telecommunications and SCADA data path.

OCS

Overhead Contact System. The overhead wiring on an electrified railway — contact wire, messenger wire and droppers — that supplies traction power to trains, sometimes referred to as catenary.

Axle counter

A trackside train detection system that counts wheel axles entering and leaving a defined section of track to determine whether it is occupied, used as an alternative or complement to track circuits.

Balise

A trackside transponder, typically mounted between the rails, that transmits fixed location and data telegrams to a passing train's onboard equipment as part of the train control and signalling system.

Definitions are provided for general reference. Always confirm exact terminology, ratings and applicable standards against your project's technical specification.