—Power cable
(a type of electrical cable) is an assembly of two or more electrical
conductors held together with, and typically covered with, an overall sheath.
The conductors may be of the same or different sizes, each with their own
insulation and possibly a bare conductor. Larger single conductor insulated
cables are also called power cables in the trade. The sheath may be of metal,
plastic, ceramic, shielded, sunlight-resistant, waterproof, oil-resistant,
fire-retardant, flat or round, and may also contain structural supports made of
high-strength materials.
Cables are usually classified according to their operating voltage as follows:
1.Low
voltage cables (up to 1kv).
2.Medium
voltage cables (3kv up to 30kv).
3.High
voltage cables (66kv up to 500kv).
Cable Construction
The general construction of the cable is
given below
1.conductor
2.Insulation
3.Assembly
4.Bedding
5.Armouring
6.sheath
Comparison
Between Copper And Aluminum
Aluminum
requires larger conductor sizes to carry the same current as copper. For
equivalent capacity, aluminum cable is lighter in weight and larger in diameter
than copper cable.
Comparison
between single core and multicore cables:
For
same cross sectional area, single core cables Ampacity
is greater than that of multi-core cables. But from economics point of view
multicore cables are preferred.
Insulation
The
selection of a particular type of insulation to be used depends upon the
purpose for which the cable is required and qualities of insulation to be aimed
at. The following are the chief types of insulation groups that can be used:
1.
Rubber
2.
Polyethylene
3.
Polyvinyl chloride (PVC)
4.
Fibrous material
5.
Silk, cotton, enamel.
6.
XLPE
Armouring
Steel-Tape
Armouring
A
steel tape is provided over the bedding but They are not very flexible, and
their use is
limited where bending of the cables cannot be avoided.
Wire
Armouring
It
has been found that a single layer of wire Armouring
provides better mechanical protection as against two layers of steel tape.
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