Learning the Lingo: Standard IEEE Terminology

Engineers hear and use many terms associated with power-quality issues, but there is often confusion as to the precise meaning of the common words and phrases. Some of the more common ones-brownout, transient, spike, surge and dip-are inaccurate and do not adequately reflect the true duration and magnitude of power-quality disturbances.

01/01/2001


Engineers hear and use many terms associated with power-quality issues, but there is often confusion as to the precise meaning of the common words and phrases. Some of the more common ones-brownout, transient, spike, surge and dip-are inaccurate and do not adequately reflect the true duration and magnitude of power-quality disturbances. The definitions of the terms as used in IEEE 1159 are as follows:

  • Transient. An increase in voltage of up to eight times the nominal voltage level of very short duration, on the order of microseconds.

 

  • Instantaneous voltage sag or swell. A decrease (sag) or increase (swell) in voltage that lasts from 0.5 to 30 cycles with a magnitude of 0.1 to 0.9 times the nominal voltage levels.

 

  • Momentary voltage sag or swell. A decrease or increase in voltage generally having the same magnitudes as the instantaneous events, but with a duration of from 30 cycles to 3 seconds.

 

  • Temporary voltage interruption. A complete loss of voltage lasting from 3 seconds to one minute.

 

  • Sustained undervoltage. A decrease in voltage of between 0.8 and 0.9 times the nominal voltage for a period greater than one minute.

IEEE 1159-1995: Characteristics of Electromagnetic Phenomena


CategoryTypical DurationTypical Magnitude


Transients


Impulsive


nsec. to msec.


na


Oscillatory


3 msec. - 5 usec.


0-8 per unit (pu)


Short-Duration Variations


Instantaneous Sag


0.5-30 cycles


0.1-0.9 pu


Instantaneous Swell


0.5-30 cycles


1.1-1.8 pu


Momentary Interruption


0.5 cycles-3 sec.


less than 0.1 pu


Momentary Sag


30 cycles-3 sec.


0.1-0.9 pu


Momentary Swell


30 cycles-3 sec.


1.1-1.4 pu


Temporary Interruption


3 sec.-1 min.


less than 0.1 pu


Temporary Sag


3 sec.-1 min.


0.1-0.9 pu


Temporary Swell


3 sec.-1 min.


1.1-1.4 pu


Long-Duration Variations


Sustained Interruption


& gt;1 min.


0.0 pu


Undervoltage


& gt;1 min.


0.8-0.9 pu


Overvoltage


& gt;1 min.


1.1-1.2 pu


Voltage Imbalance


steady state


0.5-2%


Waveform Distortion


DC Offset


steady state


0.0-0.1%


Harmonics


steady state


0-20%


Inter-harmonics


steady state


0-2%


Notching


steady state


na


Noise


steady state


0-1%


Voltage Fluctuations


intermittent


0.1-7%


Power Frequency Variations


&10 sec.


na





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