Page 475 - Industrial Power Engineering and Applications Handbook

Testing of metal-enclosed switchgear assemblies 14/449
it is designed. For the purpose of design, the peak shutdown. For the purpose of design, the peak ground
ground movements should not be considered to be movements should not be considered to be less than
less than 0.1 g (IEE 344). The object should function 0.5 g (IEEE 344). In other words, equipment
normally during and after the earthquake without conforming to this test is capable of safely shutting
malfunctioning or affecting the safety and the integrity down the whole plant and maintaining it in the event
of the nuclear plant throughout its operating life. All of an earthquake of this intensity. It will also be able
the equipment installed in a nuclear power plant must to perform its duties when normal conditions are
undergo this level of testing. restored. Such equipment is subjected to at least five
2 Safe shutdown earthquake (SSE) test This is defined OBE tests before applying the SSE test. The logic
by the most severe earthquake that could occur, behind such a stipulation is a statistical study of
producing the maximum vibratory ground movements earthquakes which suggested a higher probability of
at the place of installation. Safety-related machines, moderate-intensity earthquakes and a lower probability
devices and components should remain functional for the most severe earthquakes. A small earthquake
during an earthquake of this magnitude and maintain may occur on more than one occasion for which the
the safety and integrity of the plant until a safe test object must be suitable, whereas the most severe
earthquake may occur only once in lifetime.

14.6.7 Test equipment
This is a shake table, dynamically balanced, consisting
of a platform on which the test object is mounted (Figure
14.24(a)). Special arrangements may be required to
accommodate very large objects, such as rotating
machines, motors, generators turbines and transformers,
except extremely large machines, where it may be
impractical to establish such laboratory test facilities.
UoR, India, possesses a shake table of 3.5 m x 3.5 m
with a payload capacity of up to 20 tonnes. It is provided
with electrohydraulic actuators with feedback controls
suitable to develop the required one horizontal and one
vertical movement of the test table up to 3 g (ZPA). The
test 'is usually conducted for a time history compatible
with the RRS between a frequency range of 0.2-SO Hz.
The TRS is calculated conventionally at 74 frequency
points, as recommended by the United States Nuclear
Regulatory Commission (USNRC). The time duration,
considered at about 20 seconds, will be adequate for the
attack and decay periods of the shake table. Of this, the
duration of a strong movement is considered for at least
Figure 14.24(a) Panels mounted on a shake table during seismic
tests at UoR 15 seconds, as illustrated in Figure 14.24(b). Time of

I 100 sarnpleskec I

I I
Time (Seconds) -
0.00 2.00 3.00 4.00 6.00 8.00 10.0 12.0 14.0 16.0 18.0 20.0
4 Rise time Strong motion time (>15 sec.) -C-~ecay time 4

Note The TRS will envelop the RRS by minimum 10%
Figure 14.24(b) Typical time history (RRS) of shake table movements during a laboratory test