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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