Start-Up Supervision - ABB REM 610 Technical Reference Manual

1MRS 755537
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 element, 48/14, detects overcurrent, caused by an
overload or a short circuit, for instance. When one or several phase currents exceed
the set pickup value of element 48/14, the element will generate a pickup signal after
a ~ 55 ms' pickup time. When the set operate time elapses, the element will generate
a trip signal.
The overcurrent element will be reset when all three phase currents have fallen
below the set pickup value of the element. The resetting time depends on how sharp
the drop is: if the phase currents fall below 0.5 x 48/14 PICKUP, the element will be
reset in 10 ms; if the phase currents fall below 48/14 PICKUP but not below 0.5 x
48/14 PICKUP, the element will be reset in 50 ms.
It is possible to block the tripping of the low-set overcurrent element 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!
Element 48/14 based on definite time cannot be used concurrently with element (48/
2
14 PICKUP) x (48/14 TDLY)
Note!
When element 48/14 picks up during motor start up, no pickup signal will be
generated.
Start-up supervision based on thermal stress calculation
Element (48/14 PICKUP)
thermal stress, caused by a locked rotor during motor start up, for instance. The
element can be set to pickup either when the conditions for motor start up are met or
when one or several phase currents exceed the set pickup value. The selection is
made in SGF3.
When element (48/14 PICKUP)
calculation has been set to pickup when the conditions for motor start up are met,
the element will calculate the thermal stress value, I
for motor start up are met and compare it to a reference value, (48/14 PICKUP)
(48/14 TDLY). The reference value is set to equal the amount of thermal stress built
up during a normal start up of the motor. The element will not generate a separate
pickup signal. When the reference value is exceeded, the element will generate a trip
signal. The element will be reset in 240 ms after the motor start up has ended and the
motor is running.
When element (48/14 PICKUP)
calculation has been set to pickup when one or several phase currents exceed the set
pickup value (Ip>48/14 PICKUP), the element will generate a pickup signal after a
based on thermal stress calculation
2
x (48/14 TDLY)
based on thermal stress calculation
2
x (48/14 TDLY) based on thermal stress
2
x (48/14 TDLY) based on thermal stress
REM 610
.
2
x t, for as long as the conditions
detects
2
x
29