ABB RELION REX640 Technical Manual page 1589

1MRS759142 C
REX640
Technical Manual
could be possible. The feature can be enabled with Temporary damping setting. The
available options are "True" and "False".
An example of the feature is shown in
60 A, the parallel resistor is disconnected and the target position is at 110 A. Before
the controller starts moving the coil, it estimates if the zero-sequence voltage at target
position is below the V Res maximum setting and if the movement is allowed. If the
conditions allow, the controller starts moving the coil towards the higher current.
While the movement stops at V Res maximum (set to 3.5 percent of the system's
nominal phase-to-earth voltage in this example), the controller automatically
connects the parallel resistor and moves the coil to the desired inductive current
position (that is, 110 A). After the coil has reached the target position, the controller
automatically disconnects the resistor, that is, returns it to its original connection state
while simultaneously obtaining the target position of 110 A with the parallel resistor
disconnected.
4.5
4.0
V Res maximum
3.5
Initial position = 60A
3.0
2.5
2.0
1.5
1
20
GUID-1976DC8E-1594-4320-B900-B978769FAFEF V1 EN
Figure 823: Damping of the resonance curve by using the parallel resistor
The number of maximum tuning cycles can be limited with Tuning cycles setting. The
delay between consecutive tuning cycles is controllable by setting Tuning cycle
delay. After the maximum number of tuning cycles is reached, the tuning procedure
can be started by activating the ST_TUNING input, for example, via HMI application.
The counter for maximum tuning cycles is reset after a successful tuning operation.
The ALARM output is a general problem indication during the tuning process. Usually,
it is an indication of not obtaining a required minimum level or change of zero-
sequence voltage during the coil movement. The reason for this might be, for example,
a very symmetrical network. Other reasons for the ALARM indication are coil
Figure 823
Resistor ON
40 60 80
Coil inductive current [A]
Section 9
Control functions
where the initial coil position is at
Resistor OFF
Target position =
110A
100 120 140
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