9

Cables, Wires and Cable

Installation Practices

Cables provide a highly reliable and compact method of transmitting power from its source to its
consumer. Cables are installed in open air on racks or ladders, in the ground, or underwater as in
the case of submarine cables. Power at all the voltages normally encountered in the oil industry i.e.,
less than 100 V and up to 33 kV, can be transmitted efficiently by single and multi-core cables.

Over the last 30 years there has been a progressive improvement in the materials used in the
construction of cables, especially in the non-metallic materials. This has been due to several necessary
requirements e.g.,

a) To maximise the conductor temperature and hence the power transmitted.

b) To provide high resistance to mechanical wear and tear, both during the laying of the cables, and
in their on-going use when they may be disturbed in the future.
c) To withstand the effects of chemical attack from their environment e.g., when laid in pol-
luted ground.

d) To withstand the damaging effects of steady state and transient overvoltages.

e) To withstand the impact of heat from the environment when exposed to fire and high radiant

temperatures.

f) To withstand freezing temperatures and embrittlement.

g) To be resistant to ultraviolet light when exposed to bright sunlight.

Not all of the above requirements are needed for a particular plant. The specification of the
cable and its materials should take account of the changes in its environment throughout a one-year
cycle. The conductor current rating should be based on the worst-case conditions if the cable is to
be fully utilised and expected to give a long life time of service.

9.1 Electrically Conducting Materials used in the Construction of Cables

Cables 9.2 Electrically Non-Conducting Materials used in the Construction of

References 1 and 2 give detailed information about the metallic materials used in cables. Some of
the more commonly used data are presented herein.

Handbook of Electrical Engineering: For Practitioners in the Oil, Gas and Petrochemical Industry. Alan L. Sheldrake
2003 John Wiley & Sons, Ltd ISBN: 0-471-49631-6