ETL 1110-2-533
30 Sep 94
control over the operation of these systems. The
provided with emergency power. For additional
Federal Telecommunications System (FTS 2000) in
information, see paragraphs B-4a, B-4d, and B-4e.
many locations is independent of the public switch
network telephone system, but this independence at
g.
Miscellaneous systems.
some remote sites, such as dams, should be verified.
Little information on problems with traffic congestion
(1) Sump pump system. The consequences of
for this system is available in the public domain so
the failure of the sump pumps on system protection
these systems should not be relied upon as the pri-
and safe shutdown should be evaluated. Some flood-
mary means of communications in an emergency
ing can be expected from the failure of noncritical
unless their postearthquake performance can be
piping systems. If flooding resulting from the mal-
determined.
function of the sump pumps would affect critical
systems, the pumps should be provided with emer-
(2) If access to a Corps of Engineers microwave
gency power. In addition, the anchorage of the pump
system is available at a site, it should provide a reli-
should be checked.
able means of contacting the command system.
Microwave equipment at the site should be anchored.
(2) Critical access roads. Situations could arise
The structural integrity of the entire system should be
in which repair crews and materials may have to be
ensured, that is, from the microphone or terminal to
brought into the site to mitigate a critical situation.
the antenna. Generally, microwave towers have
Some damsites may be located such that landslides or
performed well in earthquakes. Their most signifi-
bridge damage may make it difficult or impossible to
cant vulnerability is the disruption of commercial
respond in a timely manner. As part of the hazard
power and malfunction of emergency backup power
evaluation, access for offsite equipment needed for
sources. Anchorage issues were discussed in
postearthquake recovery of project lifelines should be
paragraph B-4d.
evaluated. Mitigation measures to reduce this risk
may be very costly, but mitigation through contin-
(3) If the microwave system is to provide the
gency plans that evaluate alternative sources of sup-
primary means for outside communications, relay
ply may be practical.
towers should be provided with emergency back-up
power. In addition, the system nodes should be
(3) Relays. The malfunction of a relay can
manned around the clock so that requests for assis-
cause undesirable consequences. Relays are seismi-
tance or advisories can be acted upon quickly. One
cally rugged so that they are unlikely to be damaged;
of the disadvantages of this system is that the number
however, the performance of the relays is subject to
of nodes that can be accessed is limited, but hope-
vibration-induced chatter. There are two broad
fully these would include the critical locations. An
classes of relays: protective relays and auxiliary
attempt should be made to verify that there are no
relays. Many protective relays are inherently sensi-
hidden dependencies in the microwave system. For
tive to vibration-induced changes of state; however,
example, some links of the system make use of the
their operation will initiate an orderly shutdown
public switch network (which may not be a reliable
sequence. Most auxiliary relays are not overly sensi-
link in a seismic event). All nodes should be shel-
tive to vibration-induced chatter or change of state,
tered in seismically adequate structures and need to
but their inadvertent operation may cause inappropri-
have adequate, seismically secure emergency power.
ate responses yielding system hang-up or damage.
Emergency batteries and back-up engine generators
Chatter or change of state of most auxiliary relays
were discussed in paragraph B-4a.
will not impact system operation adversely. Check-
ing of all relays to determine the impact of their
malfunction is a costly and time-consuming task, and,
f. Radio system for offsite communications. A
in general, would not be warranted. The evaluation
radio-based system is an alternate method for com-
of the emergency power system may be justified.
munication with offsite locations. Most of the com-
Some relays have been identified to be more sensitive
ments about the onsite radio communications and
to vibration in critical applications in the nuclear
microwave system also apply to radio systems.
power industry.
These systems should be adequately anchored and
B-12
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