What is medium voltage cable?

Medium Voltage cables, or MV cables, is a category defined by the International Electrotechnical Commission (IEC) as having a voltage rating of above 1kV up to 100kV. 

There does, however, remain some ambiguity over where the medium voltage cable band begins and ends, depending on the countries, the standard setting bodies, and the type of system used as historically engineers only referred to low voltage and high voltage. 

The concept of medium voltage was only introduced as the level of voltages increased and the need arose for a greater classification range, which now often includes extra low and extra high voltage.

ZMS cable is a leading supplier of medium voltage cables, which we consider to range between 3.3kV and 35kV. Our MV XLPE insulated cables are manufactured in accordance with various British and international Standards. 

These include armoured cable to British Standard BS6622 and BS7835; international Standards including IEC 60502-1 and IEC 60502-2; as well as a wide range of international construction specifications, including N2SXY, N2XS2Y, N2XSEY, NA2XSY and NA2XS2Y.

Construction of medium voltage MV cable

Cross-sectional area: generally 35mm2 up to 100mm2

Number of cores: generally one or three

Solid or stranded aluminium conductors: for applications requiring a lighter cable weight, also often more economical due to lower aluminium prices.

Stranded copper conductors: for applications requiring a smaller overall diameter and higher transmitting properties.

Bedding

Bonded or strippable out semi-conducting layer

Water tightness: longitudinal, longitudinal + quasi-radial, longitudinal + radial

Insulation layers (conductor screen, insulation and insulation screen): XLPE, which is more commonly used for MV cables, or EPR which is more flexible and often better suited to marine and offshore applications.

Metallic screen: to nullify the electric field outside the MV cable. Concentric copper wire screens, Aluminium foil laminate, or extruded lead alloy sheath.

Twisted three-core cable or triplex

Armouring: for mechanical protection. Aluminium wire armoured for single-core cables, Galvanised steel wire armour, strip or tape.

Tapes: Separator tapes to facilitate peeling, water-swellable tapes to prevent water ingress, Conductive tape for core binding.

Outer Sheath: compounds with various properties, tailored to the specific application's requirements, including resistance to oils, greases, rodents, termites, UV and flame, as well as zero halogen emissions.

6.35/11kV MV cable

Application:

Power cables for power networks, underground and in cable ducting

Construction:

Conductor

Class 2 stranded copper conductor according to BS EN 60228 (previously BS 6360)

Conductor Screen

Semi-conductive XLPE (Cross-Linked Polyethylene)

Insulation

XLPE (Cross-Linked Polyethylene) Type GP8 according to BS 7655

Insulation Screen

Semi-conductive XLPE (Cross-Linked Polyethylene)

Metallic Screen

Individual or collective overall copper tape screen according to BS 6622

Filler

PET (Polyethylene Terephthalate) fibres Separator

Binding tape

Bedding PVC (Polyvinyl Chloride) Type TM1 according to BS 7655

Armour

Single core: AWA (Aluminium Wire Armoured) Multi-core: SWA (Steel Wire Armoured)

Sheath

PVC (Polyvinyl Chloride) Type TM1 according to BS 7655

Characteristics

Voltage Rating

(Uo/U)(Um) 6.35/11 (12)kV

Temperature Rating

Fixed: 0°C to +90°C Minimum

Bending Radius

Single core - Fixed: 15 x overall diameter 3 core - Fixed: 12 x overall diameter (Single core 12 x overall diameter and 3 core 10 x overall diameter where bends are positioned adjacent to a joint or termination provided that the bending is carefully controlled by the use of a former)