ANSI05000016-2-en.vsd
Voltage
IDMT Voltage
Time
VA
VB
VC
ANSI05000016 V2 EN-US
Figure 332: Voltage used for the inverse time characteristic integration
Operation of the trip signal requires that the overvoltage condition continues for at least the user
set time delay. This time delay is set by the parameter
t1
and
t2
for definite time mode (DT) and by
selected voltage level dependent time curves for the inverse time mode (TOV). If the PICKUP
condition, with respect to the measured voltage ceases during the delay time, and is not fulfilled
again within a user defined reset time (
tReset1
and
tReset2
for the definite time and
tIReset1
and
tIReset2
for the inverse time) the corresponding PICKUP output is reset, after that the defined
reset time has elapsed. Here it should be noted that after leaving the hysteresis area, the PICKUP
condition must be fulfilled again and it is not sufficient for the signal to only return back to the
hysteresis area. The hysteresis value for each step is settable
HystAbsn
(where
n
means either 1 or
2 respectively) to allow a high and accurate reset of the function. For OV2PTOV (59) the TOV reset
time is constant and does not depend on the voltage fluctuations during the drop-off period.
However, there are three ways to reset the timer: either the timer is reset instantaneously, or the
timer value is frozen during the reset time, or the timer value is linearly decreased during the reset
time.
1MRK 502 066-UUS B Section 9
Voltage protection
619
Technical manual
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