TM 5-852-5/AFR 88-19, Volume 5
POWER DISTRIBUTION AND COMMUNICATION SYSTEMS
grid into a nearby lake.
The basic design requirements for wire and cable
11-3. Underground Systems.
networks for power transmission and communica-
tion Systems are not unique in the cold regions and
Power and communication networks have been
TM 5-811-1/AFM 88-9, Chap. 1, should be used for
successfully installed in the utilidor systems des-
the design of these systems. Special concern is
cribed in chapter 8. The direct burial of cables in the
needed to ensure proper grounding in permafrost
active layer in frost-susceptible soils must be
areas, to maintain stability of towers, poles, guy
avoided. The freezing and expansion of these soils
wires and anchors, and for direct burial of cables.
will result in structural failure of the cable or severe
mechanical damage. Buried conduits or ducts must
be placed in non-frost-susceptible backfill materials.
Prime consideration will be given to placing a gravel
Areas with permafrost do not provide acceptable
and non-frost-susceptible material pad on the
grounding conditions due to the high resistance of
existing ground surface and burying the cables in
frozen ground. In these locations all the facilities are
this new pad if a buried system is required. As
tied together, including electrical wiring, petroleum,
shown in figure 11-1, the gravel pad also serves as
oil, and lubricant (POL) piping metal building, POL
a road or walkway.
storage tanks, water and sewer lines, etc., to form
one large grid network. This network is then
11-4. Aerial Systems.
connected to a water well casing that penetrates the
permafrost layer and results in an acceptable
Ice buildup will be a problem for aerial cables,
ground. If no well casing exists, the grid system is
particularly in coastal locations. Preventive mea-
connected to a ground rod that does not penetrate
sures have included the use of a steel conductor to
the permafrost. This will provide a common floating
ground with everything at the same electrical
thawing. The major engineering problem with aerial
potential. This is an acceptable approach as long as
systems in the cold regions is the stability of the
everything is bonded to that common ground.
supporting towers or poles. The upper soil layer,
Another possibility is to place a grounding cable
known as the active zone, goes through a freezing