ABB 615 Series ANSI, Technical Manual

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1MAC050144-MB C
Section 4
Protection functions
615 series ANSI 205
Technical Manual
Figure 96: Functional module diagram
Level detector
The calculated negative-sequence current is compared to the Pickup value setting. If the
measured value exceeds the Pickup value setting, the function activates the timer module.
Timer
Once activated, the timer activates the
PICKUP
output. Depending on the value of the set
Operating curve type , the time characteristics are according to DT or IDMT. When the
operation timer has reached the value set by Trip delay time in the DT mode or the
maximum value defined by the inverse time curve, the
TRIP
output is activated.
In a drop-off situation, that is, when the value of the negative-sequence current drops
below the
Pickup value setting, the reset timer is activated and the
PICKUP
output resets
after the time delay of Reset delay time for the DT characteristics. For IDMT, the reset time
depends on the curve type selected.
For the IDMT curves, it is possible to define minimum and maximum trip times with the
Minimum trip time and Maximum trip time settings. The Machine time Mult setting
parameter corresponds to the machine constant, equal to the I
2
2
t constant of the machine,
as stated by the machine manufacturer. In case there is a mismatch between the used CT
and the protected motor's nominal current values, it is possible to fit the IDMT curves for
the protected motor using the
Rated current setting.
The activation of the
TRIP
output activates the
BLK_RESTART
output. The deactivation
of the
TRIP
output activates the cooling timer. The timer is set to the value entered in the
Cooling time setting. The
BLK_RESTART
output is kept active until the cooling timer is
exceeded. If the negative-sequence current increases above the set value during this
period, the
TRIP
output is activated immediately.
The operation timer counting can be frozen to the prevailing value by activating the
FR_TIMER
input.
The
T_ENARESTART
output indicates the duration for which the
BLK_RESTART
output
remains active, that is, it indicates the remaining time of the cooling timer. The value is
available through the Monitored data view.
TRIP
BLK_RESTART
PICKUP
BLOCK
I
2
Level
detector
Timer