ABB RELION REX640 Technical Manual page 1571

1MRS759142 C
REX640
Technical Manual
Command error
OL5ATCC supervises the tap changer position information of the own transformer
when a control pulse is given. If the correct position change (direction depends on the
comparison of the settings Raise block tap and Lower block tap) is not seen by
OL5ATCC in Cmd error delay time after the pulse start, the alarm is issued.
If the position information is not connected, no alarm is generated. The alarm is reset
when the correct change in position value is detected after a given pulse or if a new
command pulse is given.
The monitored data ALARM_REAS is set during an alarm. This means that if the
alarm reason is active, ALARM_REAS has the value "Cmd error".
TCO signal fails
If the tap changer operating signal TCO stays active for more than 15 seconds after the
output pulse deactivation, OL5ATCC sees this as an abnormal condition and assumes
that the tap changer is stuck. The alarm is reset when the TCO input signal deactivates.
The monitored data ALARM_REAS is set during the alarm. This means that only if
alarm reason is active, ALARM_REAS has the value "TCO error".
If the TCO input signal is not connected (indicated by bad quality), this type of alarm
is not possible.
Regulator pumping
Faulty settings may cause the regulator to give control pulses too frequently. For
example, too low a setting for the Band width voltage
pumping condition where the regulator has problems to bring the regulated voltage to
a desired level. To detect this, OL5ATCC has a setting Max operations in 1h, which
defines the allowed number of lowering and raising commands during a one-hour
sliding time window. The detection is active both in the manual and automatic
operation modes. The alarm is reset after the number of operations during the one-
hour time window is less than the set value. The number of executed operations of the
last one hour can be read from the monitored data OP_TM_NUM_H. However, this
parameter is updated only in three-minute intervals. The monitored data
ALARM_REAS is set during an alarm. This means that only if alarm reason is active,
ALARM_REAS has the value "Pump error".
The operation of OL5ATCC is not blocked during an alarm situation, but all the
alarms mentioned above cause the automatic operation to be delayed, which means
that the set delay times T1 and T2 are doubled.
In addition to the alarm detections, OL5ATCC provides a nonvolatile operation
counter parameter (monitored data OPR_CNT) for determining the service intervals
of the tap changer. The counter gives the total number of raising and lowering
commands given in the manual and automatic modes. All commands, even those that
are omitted by the tap changer due to its operation sequence, are calculated in a
cumulative counter. This data parameter can be reset via the parameter OL5ATCC
counter on the Clear menu.
Section 9
Control functions
(Figure 812) can result in a
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