When the operation timer has reached the value set by
Operate delay time in the DT
mode or the maximum value defined by the IDMT, the
OPERATE
output is activated.
When the user-programmable IDMT curve is selected, the operate time
characteristics are defined by the parameters
Curve parameter A, Curve parameter
B, Curve parameter C, Curve parameter D and Curve parameter E.
If a drop-off situation occurs, that is, a fault suddenly disappears before the operate
delay is exceeded, the reset state is activated. The behavior in the drop-off situation
depends on the selected operate time characteristics. If the DT characteristics are
selected, the reset timer runs until the set
Reset delay time value is exceeded. If
the drop-off situation exceeds the set
Reset delay time, the Timer is reset and the
START
output is deactivated.
When the IDMT operate time curve is selected, the functionality of the Timer in the
drop-off state depends on the combination of the
Type of reset curve, Type of time
reset and Reset delay time settings.
Table 792: Reset time functionality when IDMT operation time curve selected
Reset functionality
Setting Type of
reset curve
Setting Type of
time reset
Setting Reset
delay time
Instantaneous
reset
Operation timer
is “Reset instan-
taneously” when
drop-off occurs
“Immediate”
Setting has no
effect
Setting has no
effect
Frozen timer
Operation timer
is frozen during
drop-off
“Def time reset”
“Freeze Op tim-
er”
Operate timer is
reset after the
set
Reset delay
time
has elapsed
Linear decrease
Operation timer
value linearly de-
creases during
the drop-off sit-
uation
“Def time reset”
“Decrease Op
timer”
Operate timer is
reset after the
set
Reset delay
time
has elapsed
1MRS759142 F
Protection functions
REX640
Technical Manual
861