ABB Relion REG670, Technical Manual

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EQUATION1440 V1 EN
(Equation 121)
The details of the different inverse time characteristics are shown in section "Inverse
characteristics" .
TRIP signal issuing requires that the residual 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 some special voltage level dependent time curves for
the inverse time mode (IDMT).
If the START 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
START output is reset, after that the defined reset time has elapsed.
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.
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. See figure
236 and figure 237 .
Section 9
1MRK502052-UEN B
Voltage protection
510
Technical manual