Start-Up Supervision - ABB REM 610 Technical Reference Manual

1MRS 752263-MUM
4.1.4.3.
Motor protection Relay
Technical Reference Manual

Start-up supervision

Start-up supervision can be based on either definite-time overcurrent protection or
thermal stress calculation. The selection is made in SGF3, the default being thermal
stress calculation.
Start-up supervision based on definite-time overcurrent
protection
The non-directional low-set stage, I
a short circuit, for instance. When one or several phase currents exceed the set start
value of stage I >, the stage will generate a start signal after a ~ 55 ms' start time.
s
When the set operate time elapses, the stage will generate a trip signal.
The overcurrent stage will be reset when all three phase currents have fallen below
the set start value of the stage. The resetting time depends on how sharp the drop is:
if the phase currents fall below 0.5 x I
currents fall below I > but not below 0.5 x I
s
It is possible to block the tripping of the low-set overcurrent stage by applying a
digital input signal to the relay.
A disadvantage of start-up supervision based on definite-time overcurrent protection
is that the operate time is fixed and cannot be extended during low-voltage
conditions.
Note!
Stage I > cannot be used concurrently with stage I
s
Note!
When stage I > starts during motor start up, no start signal will be generated.
s
Start-up supervision based on thermal stress calculation
2
Stage I x t detects thermal stress, caused by a locked rotor during motor start up,
s s
for instance. The stage can be set to start either when the conditions for motor start
up are met or when one or several phase currents exceed the set start value. The
selection is made in SGF3.
2
When stage I x t has been set to start when the conditions for motor start up are
s s
met, the stage will calculate the thermal stress value, I
conditions for motor start up are met and compare it to a reference value,
2
I x t . The reference value is set to equal the amount of thermal stress built up
s s
during a normal start up of the motor. The stage will not generate a separate start
signal. When the reference value is exceeded, the stage will generate a trip signal.
The stage will be reset in 240 ms after the motor start up has ended and the motor is
running.
2
When stage I x t has been set to start when one or several phase currents exceed
s s
the set start value (I >I
L s
time and calculate the thermal stress value, I
fallen below the set start value. When the calculated value exceeds the reference
2
value, I x t , the stage will generate a trip signal. The stage will be reset in 240 ms
s s
after all three phase currents have fallen below the set start value of the stage.
>, detects overcurrent, caused by an overload or
s
>, the stage will be reset in 10 ms; if the phase
s
>, the stage will be reset in 50 ms.
s
), the stage will generate a start signal after a ~ 100 ms' start
2
x t, until all three phase currents have
REM 610
2
x t
s s.
2
x t, for as long as the
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