Components of an electrical cable
As an element that transmits electricity

As an element that transmits electricity, an electrical cable is basically made up of two parts: a conductor transmitting the electrical current and an insulation material that maintains this electrical current within the conductor. In addition, the cable can have other auxiliary elements, generally mechanical protection, which guarantees a long work life for the cable under normal operating conditions.

The electrical current flows through the conductor and this make the conductor as the only vital element in an electrical cable. It is always made of metal, the most commonly used being copper.

The main advantages of this material is that it is a good electrical conductor and this material is found naturally in relative abundance., The processing procedure is fact that it is uncomplicated and it can maintain its characteristics over long periods of time (low chemical reactivity).

In some cases, as a result of cost issues, aluminium conductors are also used. This metal has a lower electric conductivity than copper (for the same section it has a much higher Joulean loss rate). However, its price makes it competitive even though much greater sections have to be used for a given power supply.

Aluminium cables are practically never used for electrical installations in industry as aluminium is difficult to process and impossible to fine draw. Flexible aluminium cables cannot be found in the market. Rigid aluminium cables are difficult to install. In addition, the connections tend to become loose over a period of time and hence it is necessary to perform maintenance inspections from time to time. In short, only the large-scale operators (utility companies) purchase aluminium cables as it is more cheaper for them .

The insulation layer surrounds the conductor and insulates it from external contacts. With reference to thermal properties, insulation materials can be divided into two large groups: thermoplastics and thermosetting materials.

Thermoplastic material softens when temperature increases. PVC is widely used for thermoplastic insulations and, has a maximum working temperature of 70 °C. It becomes soft at 160 °C.

Thermosetting material does not fuse when temperature increases (although it will degrade and burn if the temperature increases excessively). To attain this property, the polymers must be crosslinked (or vulcanised) during the production process. The most widely used thermosetting materials for insulating purposes (XLPE and EPR) have maximum working temperatures of 90 °C and can withstand up to 250 °C for short periods of time.

Some cables can be supplied with metallic layers, which can be either electrical or mechanical called protection. Electrical protection is named screening and is applied to avoid electrical interference. It can be copper wire braid (plain or tinned copper) or Al-polyester tape. These screens are applied over the twisted insulated conductors.

Mechanical protection, called armour , is applied to protect conductors against possible external damage (such as knocks and rodents). It can be of steel or Aluminium (non-magnetic). Aluminium armour is used in single core cables in order to avoid eddy currents, which could result in an unwanted overheating of the cable.

Finally, all the cables are manufactured with an outer sheath. This protects the interior of the cable, where the electricity flows, against external elements (knocks, chafing, the presence of humidity, etc.). In general, these outer sheaths are made of polymer materials and should be chosen in accordance with the nature of the insulation material.

To conclude, we can affirm that all cable components have an important function, and only correct cable selection will ensure the longevity and reliability of the installation.

Technical article writen by JYeo Hezron Jerome