Here it should be noted that after leaving the hysteresis area, the START condition
must be fulfilled again and it is not sufficient for the signal to only return back to
the hysteresis area. Also, notice that for the overvoltage function, IDMT reset time
is constant and does not depend on the voltage fluctuations during the drop-off
period.
There are three ways to reset the timer: the timer is reset instantaneously, the timer
value is frozen during the reset time, or the timer value is linearly decreased during
the reset time. See figure
120 and figure 121.
TRIP
U1>
TRIP
t
Time
Time
Integrator
t
Frozen Timer
Instantaneous
Voltage
Voltage
Time
HystAbs1
START
START
tIReset1
Measured
tIReset1
Linearly decreased
IEC09000055-2-en.vsd
IEC09000055 V2 EN-US
Figure 120: Voltage profile not causing a reset of the START signal for step 1, and inverse time delay
Section 9 1MRK 505 394-UEN A
Voltage protection
260 Line differential protection RED650 2.2 IEC
Technical manual
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