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.
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:
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Transient. An increase in voltage of up to eight times the nominal voltage level of very short duration, on the order of microseconds.
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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.
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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.
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Temporary voltage interruption. A complete loss of voltage lasting from 3 seconds to one minute.
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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
| 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 |
