Medium voltage

Medium Voltage Cables

Cabelte began the manufacturing of medium voltage power cables in 1983 for a Project which required the strengthening of internal technical staff and a significant investment with new buildings and equipment for production and testing..

By that time, the range of products included, namely, cables to be used on low voltage power transmission public networks and in some industrial networks.

Throughout the years, new types of cables were developed – with more demanding technical requirements, having different design characteristics and cables for different markets. One should remark, those to be applied on airports, underground railways and wind farms.

The company has been following this evolution and, nowadays, it has a wide range of references covering the different rated voltages, several national and the most important international standards and also particular specifications adopted by some customers. Additional technical requirements may also be considered to comply, for instance, with applications in harsh environment.

In 2005 Cabelte invested in new production machinery allowing to double its capacity for supplying medium voltage cables.

On the most common medium voltage power cable one can identify 4 constituent parts with distinct purposes:

- Conductors ensuring electric power transmission,
- Insulation coverings and internal and external semiconductors, simultaneously extruded, assuring the perfect level of electrical security, for specified rated voltages,
- Metallic screens to discharge defect current, to restrain the electric field and, in certain types of cables, for mechanical protection and water blocking proof,
- The coverings suitable to external cable protection considering the installation conditions.

The most common materials used on conductors are copper and aluminium, because of their high conductivity level and by the easiness of processing.

Regarding the insulation materials, cross linked polyethylene (XLPE) is the most used for its own characteristics, easy handling and low cost.

In certain special applications rubber compounds of ethylene propylene (EPR and HEPR) are also used and PVC compounds, barely and only for rated voltages up to 3,6/6kV.

Polymeric materials are used on sheaths for outer cable protection and, when a higher mechanical protection is needed, armours of metallic tapes or wires could be applied.

As exigências crescentes de segurança das pessoas e das instalações obrigaram, em muitas aplicações, à utilização de Presently, as there is a constant concern with people and building safety, many situations oblige the use of medium voltage power cables with improved fire behaviour. These fire-proof cables use sheaths of halogen free compounds that in the presence of fire release smoke and gases of low opacity, low toxicity and low corrosivity. In addition, these sheaths together with other components achieve an increased resistante to fire propagation.

The most common range of medium voltage power cables are as follows:

- Copper or aluminium single core cables
- Copper or aluminium three core cables
- Copper or aluminium three single-core cables