Basic Training Course
Basic Training Course Cables & Joints Electrical
1. General
Cables form an important part of any installation but, because they are static,
and in normal service are very reliable, they do not always receive the attention
that they deserve.
There are three categories of cables associated with industrial installations -
power cables, control cables, and special cables for, for example,
communications and data transmission circuits. It is the first two categories
which are described in this chapter. A power cable contains one, two, three or
four cores each consisting of a copper conductor surrounded by insulating
material; a control cable usually has many cores and is known as a 'multicore'
cable. Aluminium is sometimes used as a conductor material; although its
conductivity is less than that of copper, it is somewhat cheaper. Corrosion
problems, however, preclude its use on Shell installations, particularly offshore.
2 Power Cables
Cables are designed for both high voltage and low-voltage transmission of
power. Though the general construction is similar in both cases, high-voltage
cables have thicker insulation and usually have smaller conductors, since lowvoltage
cables carrying bulk power handle the heavier Currents.
2.1 General Construction
A power cable is made up of one, two, three or four insulated conductors
enclosed in a bedding . For mechanical protection, wire armouring
is wrapped around the bedding, and a coloured outer protective sheath,
usually of PVC, is extruded over the armouring, as shown in Figure 1, Each
insulated conductor is known as a ‘core',
