Environmental Engineering Reference
In-Depth Information
Wire insulation
Braided shield
Cable jacket
Foil shield
Conductor
6.1
Cable components.
components such as control switches, valve operators, relays, and contactors
(Hashemian, 2010).
A complete cabling system (see Fig. 6.1) may include any or all of the
following components: conductor, insulation, shield, jacket, terminations,
penetrations, splices, connectors, and/or end devices (sensor, transmitter,
detector, motor, etc.) (AMS Corp., 2010). However, the main components
of an I&C or low-voltage power cable are conductors, electrical insulation
or dielectric, shielding, and the outer jacket.
Power cables and I&C cables both operate by providing a conductive
route for an electric circuit by using metallic conductors - typically cop-
per or aluminum that are insulated with a polymer and have different
confi gurations such as coaxial, triaxial, twisted pair, or multi-conductor
arrangements of single-strand or bundled wires (AMS Corp., 2011; U.S.
NRC, 2001). The cable insulation and jacket are made of different poly-
mers, including polyethylene (PE), cross-linked polyethylene (XLPE),
polyvinyl chloride (PVC), ethylene propylene diene-monomer (EPDM)
rubber, ethylene propylene rubber (EPR), Hyplon, Lipalon, and others
(AMS Corp., 2010; 2011). More than three-quarters of cable insulation
and jacket used in nuclear plants is constructed from such polymers (U.S.
NRC, 2010a). Another type of cable, fi ber-optic, is used to transmit signals
based on optical fi ber technology. Though its outer jacket is similar to cop-
per and aluminum cable, fi ber-optic cables have unique ageing, degrada-
tion, and failure characteristics (U.S. NRC, 2010a). As such, they are not
covered here.
Connectors are also part of the conductor in a cable circuit. A multitude
of connectors, terminations, terminals, splices, etc., join the conductor to
other cables or electronic equipment. The failure of these components
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