Manufacturing an Electrical Cable

Electrical cables are all around us. Some are visible, like those used to connect our household appliances and office equipment to the power grid, others remain unseen, such as underground utility cables. In general, we tend to take them for granted and do not even realise how many different cable types and diameters exist. Yet, to offer years of reliable fault-free service and keep us blissfully unaware of their presence, cables undergo a complex manufacturing process.


A simple cable consists of an electrical conductor (typically copper or aluminum), which allows the electricity to flow, and insulation, which is responsible for keeping the current flow within the conductor and thus ensures there is no leakage. Depending on the purpose of a particular cable, there may be additional layers to increase the cable’s reliability and prolong its service life.

The cable manufacturing process is made up of several stages, the first one being the wire drawing. During this stage, the diameter of a wire rod is gradually reduced down to the pre-set value. After this the wire is subjected to annealing, which is basically heat treating. The purpose of annealing is to improve the wire’s physical properties, namely its ductility and conductivity.

The next stage is wiring, during which the wires are combined to create conductors of a varying cross-section. After wiring, the conductor is covered with insulating material through the process of hot extrusion. The choice of insulating material depends on the requirements the cable needs to meet. The quality of insulation is defined by its capacity and thermal resistance. The higher the capacity and thickness of the insulation are, the higher the maximum surface voltage of the cable is; in other words, the higher the thermal resistance is, the more electrical power the conductor can transmit. To make sure that the cable insulation is free from faults and does not leak any current, producers subject the whole of the cable length to voltage testing.

In the manufacturing of multicore cables the next stage is phase wiring. During this step several conductors are combined; to distinguish between the different phases, manufacturers mark them with either colours, numbers, or other marking. This stage is also concluded with voltage testing of the cable.

If the cable needs to withstand high electrical stress or highly demanding operating conditions, additional layers are used to improve its characteristics. To protect the cable from potential outside influences, its signal is insulated with screens. Steel or aluminum armour in the form of braids, wire or strips is applied to prevent the cable from possible mechanical and other types of damage.

Alternatively, the outer sheath can serve as the final layer of protection. It is typically made of various kinds of polymer according to the required protection level. The purpose of the outer sheath is to keep away the elements, for instance, moisture, and prevent the cable from mechanical impact. The sheath is applied like the insulation through hot extrusion.

At the last stage the manufactured cable goes through a complete testing cycle. To make sure the ready cable complies with the industry standards of quality, the manufacturer performs the final set of voltage testing.

KEP (KharkovEnergoPribor) supplies its cable test vans with KEP’s flexible silicone high-voltage cables that are suitable for high-voltage testing both as part of cable test vans and separately.

All the cables that KEP uses in its high voltage testing equipment undergo a thorough quality check to guarantee that the cables will work perfectly.

Alexei Tiatiushkin

Marketing manager

KharkovEnergoPribor Ltd.

marketing@keppowertesting.uk

http://www.kep.ua