Application - ABB RED615 Technical Manual

1YHT530004D05 D
9.5.15
615 series
Technical Manual
If the TCO input signal is not connected (indicated by bad quality), this type of
alarm is not possible.
Regulator pumping
It is possible that faulty settings cause the regulator to give control pulses too
frequently. For example, too low a setting for the Band width voltage
can result in a pumping condition where the regulator has problems to bring the
regulated voltage to a desired level. To detect this, OLATCC 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 counted
number of the operations during the one-hour time window is less than the set
value. The number of executed operations per last one hour can be read from the
monitored data OP_TM_NUM_H. However, this parameter is updated only in three-
minute intervals. Again, 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 OLATCC is not blocked during an alarm situation, but all the
alarms mentioned above cause the automatic operation to be delayed. In practice,
this means that the set delay times T1 and T2 are doubled.
In addition to the alarm detections, OLATCC 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 clear
menu parameter OLATCC counter.

Application

OLATCC is used to control the voltage on the load side of the power transformer.
Based on the measured voltage and current, the function block determines whether
the voltage needs to be increased or decreased. The voltage is regulated by the
raising or lowering commands sent to the tap changer.
The basic principle for voltage regulation is that no regulation takes place as long
as the voltage stays within the bandwidth setting. The measured voltage is always
compared to the calculated control voltage U
from the bandwidth, the delay time T1 starts. When the set delay time has elapsed,
a raising or lowering control pulse is sent to the tap changer. Should the measured
voltage still be outside the bandwidth after one tap change, the delay time T2 starts.
T2 is normally shorter than T1.
Under certain circumstances, the automatic voltage regulator needs to be enhanced
with additional functions such as Line Drop Compensation (LDC) and Reduce Set
Voltage (RSV). Also, various parallel operation modes are available to fit
Control functions
. Once the measured voltage deviates
p
Section 9
(Figure 397)
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