UFC 3 -520-01
June 10, 2002
Table 12-2. Power Quality Summary
Power
Example Waveform
Typical Cause
Typical Solutions
Quality Category
Impulsive
Surge protectors
transients
Capacitor switching
Filters/reactors
Load switching
Isolation transformers
Oscillatory
Capacitor switching
Surge protectors
transients
Line switching
Filters/reactors
Load switching
Isolation transformers
Sags and Swells
Remote system faults
UPS systems
Ferroresonant transformers
Switching operations
Energy storage devices
Interruptions
System fault clearing
UPS systems
Loss of generation
Backup generators
Harmonic
Nonlinear loads
Filters/reactors
distortion
System resonance
Isolation transformers
K-factor transformers
Rotary UPS
12-5.5
The following sub sections provide additional information regarding different
possible equipment types and design solutions.
12-5.5.1 Surge Protectors. Surge protectors are not normally considered a solution
for power quality problems; their principal purpose is to protect against surge transients.
Refer to Chapter 11 for surge protection criteria.
12-5.5.2 Filter Reactors.
12-5.5.2.1 Reactors can be a cost -effective solution in an existing facility where rewiring
is difficult or costly. Reactors provide a filtering function by blocking offending harmonic
12-5.5.2.2 Reactors are rated in terms of percent impedance. Higher impedance
reactors provide greater filtering, but also increase the voltage drop. For example, a 3
percent impedance reactor will introduce a 3 percent voltage drop across it under rated
conditions. Evaluate the effect of the additional voltage drop as part of any filter
12-6
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