CB_CLOSED signal. The CB_CLOSED signal is True when the CB position
is closed.
Under current detector
The Under current detector module can be enabled by setting
Enable under current
to “Enable” and disabled by setting it to “Disable”. The Under current detector
module is also disabled when CB_CLOSED is FALSE, that is, when circuit breaker is
open.
The fundamental frequency component of phase currents is compared to the
setting
Start value Un Cur
. If all the three-phase currents are below the setting
Start
value Un Cur
, the Under current detector module enables the Timer 3 module.
Timer 3
Once activated, the Timer 3 module activates the ST_UN_I output. The operation is
based on DT characteristics. When the operation timer has reached the value of
Un
Cur delay time
, the OPR_UN_I output is activated.
If the undercurrent situation disappears, the operation timer is reset. The
ST_DUR_UN_I output indicates the percentage ratio of the undercurrent start
situation and the set operation time in the Timer 3 module and is available in the
monitored data view.
The OPR_UN_I output is of pulse type and remains TRUE for 150 ms. After that,
ST_DUR_UN_I and OPR_UN_I are deactivated and ST_DUR_UN_I is reset.
If the circuit breaker closed status signal is not detected, the constant
value TRUE has to be connected to CB_CLOSED input to enable the
undercurrent detector.
If the circuit breaker status signal is not connected to CB_CLOSED input,
the OPR_UN_I output is activated even if the circuit breaker is open and
undercurrent is detected.
Inhibit reclose
When the output OPR_UN_I becomes active or when the CB_CLOSED state changes
from TRUE to FALSE, that is, when circuit breaker opens, the reclosing inhibition
module activates output BLK_CLOSE.
If
Enable under current
is set to “Disable”, the reclosing inhibition
operation is based purely on the CB_CLOSED input.
The behavior of the BLK_CLOSE output depends on
Reclose inhibit mode
. If
Reclose
inhibit mode
is set to “Lockout”, the BLK_CLOSE output needs to be reset manually
from the clearing menu parameter
COLPTOC inhibit recl
. If
Reclose inhibit mode
is
set to “Non-latched”, the BLK_CLOSE output resets after the set
Reclose inhibit time
has elapsed.
Blocking logic
There are three operation modes in the blocking function. The operation modes
are controlled by the BLOCK input and the global setting Configuration > System >
Blocking mode which selects the blocking mode. The BLOCK input can be controlled
by a binary input, a horizontal communication input or an internal signal of the IED
Protection functions
1MRS757644 H
778 620 series
Technical Manual
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