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Protection and Automation Functions
6.23 Overvoltage Protection with 3-Phase Voltage
The inverse-time characteristic is shown in the following figure.
[dwovpinv, 2, en_US]
Figure 6-182
The inverse-time delay is calculated with the following formula:
Where
T
Inverse-time delay
inv
T
Time multiplier (parameter Time dial )
p
V
Measured voltage
V
Threshold value (parameter Threshold )
thresh
k
Curve constant k (parameter Charact. constant k )
α
Curve constant α (parameter Charact. constant α )
c
Curve constant c (parameter Charact. constant c )
When V/V
is equal to or greater than 20, the inverse-time delay does not decrease any further.
thresh
Dropout Behavior
When the voltage falls below the dropout threshold (0.95 × pickup factor × threshold value), the pickup signal
is going and the dropout is started. You can define the dropout behavior via parameter Reset time . Instan-
taneous reset takes place by setting Reset time to 0 s. A delayed reset takes place by setting the desired
delay time.
During the Reset time (> 0 s), the elapsed operate delay is frozen. If the pickup value is exceeded again
within this period, the stage operates when the rest of operate delay expires.
700
Operate Curve of Inverse-Time Characteristic
SIPROTEC 5, Overcurrent Protection, Manual
C53000-G5040-C017-8, Edition 07.2017
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