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A total loss of utility power
Can be caused by a number of events:
lightning strikes, downed power lines, grid
over-demands, accidents and natural
disasters.
Short-term low voltage
Triggered by the startup of large loads,
utility switching, utility equipment failure,
lightning and power service that’s too
small for the demand. In addition to crashes,
sags can damage hardware.
Short-term high voltage
Can be caused by a lightning strike and
above 110% of nominal
can send line voltages to levels in excess
of 6,000 volts. A spike almost always
results in data loss or hardware damage.
Reduced line voltage
Can be caused by an intentional utility
extended periods few
voltage reduction to conserve power
minutes to days
during peak demand periods or other
heavy loads that exceed supply capacity.
Increased line voltage
Triggered by a rapid reduction in power
for extended periods
loads, heavy equipment being turned off,
of a
few minutes to a
or by utility switching. The results can
few days.
potentially damage hardware.
High frequency waveform
Can be caused by either RFI or EMI
caused by
EMI interference
interference generated by transmitters,
welding devices, SCR driven printers,
lightning, etc.
A change in frequency
Resulting from generator or small
stability
co-generation sites being loaded and
unloaded. Frequency variation can cause
erratic operation, data loss, system crashes
and equipment damage.
Instantaneous
Normal duration is shorter than a spike
and under-voltage (notch)
and generally falls in the range of
in the range of
nanoseconds.
nanoseconds
Distortion of the normal
Switch mode power supplies, variable
line waveform, generally
speed motors and drives, copiers and fax
transmitted by nonlinear
machines are examples of non-linear
loads
loads. Can cause communication errors,
over heating and hardware damage.
POWER PROTECTION
9 Power Problems and Their UPS Solutions
Power Problem
Definition*
Cause*
Solution
*Reference IEEE E-050R & old FIPS PUB 94
Power Failure
Single-phase
S
eries
UPS
Single-phase
S
eries
UPS
Single-
and
Three-phase
S
eries
9
UPS
Power Sag
Power Surge
(Spike)
Over-voltage
Electrical
Line Noise
Frequency
Variation
Harmonic
Distortion
1
2
3
4
5
6
7
8
9
Under-voltage
(Brownout)
Switching
Transient
