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Operation feature
The operate time of the inverse (dependent) time characteristic is inversely proportional to the
level of the voltage condition. Figure 2.23-2 shows the invers time characteristic of the OVG
element when a multiplier setting is used. The OVG element uses Equation (2.23-1) to be in
conformity to IEC 60255-127:
where,
t = operating time (seconds),
V = energizing voltage (voltage),
Vs = pickup voltage setting (voltage), and
TMS = time multiplier setting to adjust a curve
Figure 2.23-2 IDMT characteristic of OVG element
Reset feature
The user should set the time for resetting. Figure 2.23-3 shows that examples of the pick-up
and the drop-off relevant to both the fault occurrences and the operation time. The value of the
time counter furnished in the OVG1 element is incremented if faults occur.
0.100
1.000
10.000
100.000
1000.000
1 1.5 2 2.5 3
Operating Time (secs)
Applied Voltage (x Vs)
Overvoltage Inverse Time Curves
TMS = 1
TMS = 2
TMS = 5
TMS = 10
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