Page 24 - Power Quality in Electrical Systems

8 Chapter One

Interruption

Sag

Swell

Long duration variations

Impulsive transient Oscillatory transient

Harmonic distortion

Voltage fluctuations
Figure 1.5 Typical power distur-
bances, from [1.2].
[© 1997 IEEE, reprinted with
permission]
Noise

■ Another common power-quality event is “notching,” which can be cre-
ated by rectifiers that have finite line inductance. The notches show
up due to an effect known as “current commutation.”
■ Voltage fluctuations are relatively small (less than 5 percent) vari-
ations in the rms line-voltage. These variations can be caused by