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CASE STUDY 7
Transient Overvoltage
Environment:
Analysis:
Target: Factory, 3-phase 3-wire, 200V circuit
A transient overvoltage was detected in all events occurring several times during the
measurement. Unfortunately, the cause of the transient could not be determined.
Problem:
The screen of equipment does not correctly display.
Analysis of transient waveform
Occurred on all 3 phases (R-S, S-T, T-R) simultaneously.1)
Occurred twice in 1 cycle of the commercial waveform, and the interval between 2 events is
820µs.
2)
The level is between 120V to 260V peak-to-peak.3)
The frequency is between 10kHz and 30kHz.4)
The threshold set at 1/2 of the waveform peak value is effective for the transient overvoltage.
For example, set the threshold at 0.07kV for the 100Vrms circuit, and 0.14kV for the 200Vrms circuit.
Note:
Analysis of Transient Overvoltage
U1 U2 U3
Max. value
Min. value
Transient
p-p value
-116.0V
-329.3V
323.4V
153.5V
98.4V
-55.1V
213.3V 169.9V 153.5V
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