For more detailed description on IDMT curves and usage of
Curve Sat
Relative
setting, see the IDMT curves for undervoltage protection section
in this manual.
The Level detector contains a low-level blocking functionality for cases where one
of the measured voltages is below the desired level. This feature can be used
when wanting to avoid unnecessary starts and operates during, for example, an
autoreclose sequence. The low-level blocking is activated by default (Enable block
value is set to "True") and the blocking level can be set with the
Voltage block value
setting.
Timer
Once activated, the Timer activates the START output. Depending on the value of
the set
Operating curve type
, the time characteristics are selected according to DT
or IDMT.
For a detailed description of the voltage IDMT curves, see the IDMT
curves for undervoltage protection section in this manual.
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
operation delay is exceeded, the reset state is activated. The behavior in the drop-
off situation depends on the selected operation 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 603: 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
1MRS757644 H Protection functions
620 series
Technical Manual
655
To Next Page
Loading...
