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Voltage cuts
A voltage cut is detected if the distribution-network input voltage drops below the cut start threshold value and
continues until the voltage rises above the cut end threshold value.
If the meter is configured for default values, the threshold percentages are:
• Cut start (low) threshold - 75% (Unom)
• Cut end (high) threshold - 85% (Unom)
A typical voltage cut defect event is illustrated below:
1 Unom
2 RMS Input voltage
3 Cut start threshold
4 Cut duration
5 Cut magnitude
6 Cut end threshold
Voltage sags
A voltage sag is detected if the distribution-network input voltage drops below the sag start threshold value and
continues until the voltage rises above the sag end threshold value.
However, if the input voltage drops below the sag start threshold and then subsequently drops below the cut start
threshold, the sag defect is ignored as a cut start always erases a sag start.
If the meter is configured for default values, the threshold percentages are:
• Sag start (low) threshold - 90% (Unom)
• Sag end (high) threshold - 95% (Unom)
A typical voltage sag defect event is illustrated below:
1 Unom
2 RMS Input voltage
3 Sag start threshold
4 Sag duration
5 Sag magnitude
6 Sag end threshold
Voltage swells
A voltage swell is detected if the distribution-network input voltage rises above the swell start threshold value and
continues until the voltage falls below the swell end threshold value.
If the meter is configured for default values, the threshold percentages are:
• Swell start (high) threshold - 110% (Unom)
• Swell end (low) threshold - 105% (Unom)
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