ABB RELION REX640, Техническое руководство, Страница: 1702 / 1960

output data. If the own tap changer position is connected, the tap changer alarm
is activated if the tap changer does not move downwards in
Cmd error delay time
after the pulse activation. As a result, ALARM_REAS in the monitored data contains a
command error value.
The lowering control works in a similar way, as shown in
Figure 916
. In the output
data, the
LOWER_OWN
output value is TRUE. An alarm is generated if the tap changer
does not move upwards in
Cmd error delay time after the pulse activation, assuming
that the own tap changer position is connected. When doing HV side regulation, the
Lower block tap and Raise block tap are internally reversed to achieve regulation of
the primary side voltage of the transformer.
9.10.5.5 Automatic voltage regulation of single transformers (Auto single)
OL5ATCC is intended to control the power transformers with a motor-driven on-load
tap changer. The function regulates the voltage at the secondary side (or primary
side during HV side regulation) of the power transformer. The control method is
based on a step-by-step principle, which means that one control pulse at a time
is issued to the tap changer mechanism to move it exactly one position upwards
or downwards. However, when intermediate steps are not indicated for the tap
changer, it does not cause alarm if more than one step change is met.
The purpose of the regulator is to maintain a stable voltage on the regulated side
of the power transformer. The basis for this operation is the
Band center voltage
setting. By increasing or decreasing various compensation factors, the regulator
calculates a control voltage from the band center voltage as shown in
Equation
373
. Hence, the control voltage is the desired transformer regulated side voltage to
be maintained by the regulator. The control voltage is compared to the measured
voltage and the difference between the two forms the regulating process error.
Since the tap changer changes the voltage in steps, a certain error has to
be allowed. The error, called
Band width voltage, is also set by the user. A
recommended setting for
Band width voltage should be close to twice the step
voltage of the transformer ΔU
step
and never below it as a minimum. For example,
Band width voltage is twice the value of ΔU
step
in
Figure 916
.
If the measured voltage fluctuates within the control voltage ± half the
Band width
voltage setting, the regulator is inactive. If the measured voltage is outside the
half-bandwidth voltage limits, an adjustable delay T1 (
Control delay time 1 ) starts,
as shown in
Figure 916
, where the lowering function is an example. The delay T1
remains active as long as the measured voltage is outside the hysteresis limits of
half the value of
Band width voltage. The factory setting for the hysteresis is 10
percent of the set
Band width voltage.
Control functions 1MRS759142 F
1702 REX640
Technical Manual