ETL 1110-2-533
30 Sep 94
transformers. These pressure-sensitive relays, pro-
communications equipment that have in the past
vided to protect the transformer from damage due
been shown to be vulnerable to earthquake ground
to overheating, often trip due to sloshing of the
motion damage. When properly anchored, this
cooling oil during an earthquake. If this happens,
equipment performs well. However, unanchored
the wicket gates close to prevent generator runaway.
equipment can slide or overturn and experience sub-
All station power must then be provided by sources
stantial damage. Switching equipment and ceramics
in the powerhouse. This can include station service
are vulnerable to earthquake damage.
units, main units running at speed no load supplying
power to plant through reactors and transformers,
c. Emergency power. Emergency power is an
emergency generators, and batteries. If the emer-
essential feature of all Corps projects. On
gency power sources are damaged, it is possible the
hydroelectric power plant projects, batteries provide
spillway gates or other reservoir control gates
power for control systems and communication
cannot be raised. This can jeopardize dam safety if
equipment. Batteries also provide power to start
project inflows are sufficient to cause the project to
diesel-powered emergency generators. Emergency
be overtopped before the gates can be put back into
generator power is critical to most Corps projects
service. It can also jeopardize dam safety if
during system outages. These emergency
embankment dam sections have been damaged by
generators provide backup power to operate
the earthquake and the control gates cannot be oper-
spillway gates, sump pumps, and outlet works
ated to effect rapid drawdown of the impoundment.
control gates. Unanchored batteries and unanchored
Communications are also dependent on electrical
or inadequately anchored emergency generators are
power, and if the communications equipment or its
vulnerable to the damaging effects of earthquakes.
power source is damaged during the earthquake, the
project's ability to communicate emergency condi-
d. Communications equipment. Communica-
tions to upriver plants and others required to take
tions equipment plays an important role in the oper-
emergency actions would be jeopardized.
ation of Corps projects and in the response to
Therefore, the protection of onsite electrical power
emergency conditions occurring on Corps projects.
and communication is often of much greater
Communication equipment at Corps projects is
importance than that of providing electrical power
extremely vulnerable to seismic damage because of
for postearthquake recovery of communities. Onsite
its fragile nature and because it is typically
electrical power and communication during and fol-
unanchored.
lowing a major earthquake are critical to Corps
flood control projects, navigation lock projects, and
water supply projects as well as hydroelectric power
A-4. Identifying Earthquake-Vulnerable
plant projects. Therefore, many of the
Electrical and Mechanical Equipment on
vulnerabilities cited in Appendix B to this report are
Corps Projects.
applicable to all Corps projects.
b. Hydroelectric power plants. Corps hydro-
earthquake vulnerability can be accomplished by
electric power plant projects consist of dam, spill-
analytical methods, by onsite walk-through inspec-
way, and nonoverflow structures; a powerhouse
tions, or a combination of both. Analytical methods
with turbines, generators, transformers, and other
are most useful for major structures such as power-
electrical equipment; and sometimes a substation
houses, dams, and intake towers where response
with transformers and switching equipment.
spectrum analysis or time-history analyses can be
Navigation locks are often a part of Corps
used to determine the earthquake forces that are
hydroelectric power projects. The dam may be
likely to occur during a major earthquake. The
earth-fill, rock-fill, or concrete. The main structural
vulnerability of mechanical and electrical
features of power plant structures have been
equipment, however, is best assessed by walk-
designed for the inertial effects induced by
through inspections which concentrate on features
earthquake ground motions and therefore are not the
that are known from past earthquakes to be
subject of this lifeline report. Turbines and
susceptible to earthquake damage. These walk-
generators are rugged, and damage to these features
through inspections should be accomplished by a
has not occurred during past earthquakes. This
team of mechanical, electrical, and structural engi-
report focuses on the electrical, mechanical, and
neers accompanied by someone familiar with the
A-12
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