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Description / Abstract:
This guide provides cable manufacturers and users with extensive
information on the design, testing, application, and installation
of low, medium, and high-voltage power cables, as well as
communication, control and instrument cables that make use of
metal-plastic laminates as radial-moisture barriers. This guide
addresses additional means of protecting cables from the entrance
of moisture through the use of polymeric super absorbent materials
for longitudinal water blocking of stranded conductors and other
spaces within cables. The alternate use of extruded metal sheaths
or bare, longitudinally applied, metallic tapes with sealed seams
will likewise be addressed.
Purpose
While metallic sheaths, such as lead and aluminum, have been
effective in past years as barriers to moisture, their relative
cost, environmental concerns along with installation difficulties
have led to the search for alternatives. Alternatively, thin
metal-plastic foils are finding application as moisture barriers in
low, medium, high, and extra-high voltage power cables. Aluminum,
copper, or lead substrates are coated with polymeric coatings on
one or both sides and adhesively bonded to the cable jacket or over
sheath. The tapes are usually applied longitudinally, with an
overlap, or seam, that is adhesively sealed over the core of the
cable and under the jacket. In addition, other measures have been
taken to block the longitudinal movement of moisture through the
conductor and the shield interfaces so that water-impervious cables
are now available. This guide will provide information on the use
of such coated metals in cable constructions as well as the use of
other materials for longitudinal water blocking. Cable users should
find this information of value in the selection, specification,
installation, and testing of cables having radial-moisture barriers
and/or longitudinal water-blocking systems.
There is an extensive amount of information in this guide that
refers to IEC Standards, British Standards and CIGRE study group
recommendations. These organizations, and others, have developed
recommendations, standards and specifications that are pertinent to
cables with radial-moisture barriers and longitudinal water
blocking. Inclusion of a discussion of these documents presents the
user of the guide with a more complete picture of the degree to
which cables with radial and longitudinal moisture protection have
developed. The technology has matured greatly since this guide was
first published and inclusion of all pertinent information not only
serves to better inform the user of the guide but also documents
how extensive and prevalent the technology has become globally.