P
TD A
t
D
V Vpickup
B
C
Vpickup
×
=
+
-
×
-
æ
ö
ç
÷
è
ø
EQUATION1616 V1 EN
(Equation 133)
When the denominator in the expression is equal to zero the time delay will be infinity.
There will be an undesired discontinuity. Therefore a tuning parameter
CrvSatn
is set
to compensate for this phenomenon. In the voltage interval
Vpickup
up to
Vpickup
·
(1.0 +
CrvSatn
/100) the used voltage will be:
Vpickup
· (1.0 +
CrvSatn
/100). If the
programmable curve is used this parameter must be calculated so that:
0
100
CrvSatn
B
C
×
- >
EQUATION1440 V1 EN
(Equation 134)
The details of the different inverse time characteristics are shown in section
.
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 (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. Also notice that for the overvoltage function 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. See figure
and figure
Section 8
1MRK505222-UUS C
Voltage protection
520
Technical reference manual
Summary of Contents for Relion 670 series
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