Automatic Voltage Regulation Of Single Transformers (Auto Single) - ABB RELION REX640 Technical Manual

Section 9
Control functions
9.10.5.5
1546
Voltage control vs. tap changer moving direction
OL5ATCC has the control settings Lower block tap and Raise block tap which give
the tap changer position that results in the lowest and highest controlled voltage value
(usually at the LV side of the transformer). Raise block tap can be set higher than
Lower block tap and Lower block tap can be set higher than Raise block tap.
When the value of Raise block tap exceeds the Lower block tap value, the raise control
activates the RAISE_OWN output. This results in raising the tap changer position, and
the measured voltage rises. Furthermore, the RAISE_OWN output value is TRUE. If
the own tap changer position is connected (that is, the own tap changer's quality is
good), the tap changer alarm is activated if the tap changer does not move upwards
within Cmd error delay time after the pulse activation. As a result, ALARM_REAS in
the monitored data contains a command error value. The default value of the Cmd
error delay time setting is 20 seconds.
The lowering control works in a similar way, as shown in
data, the LOWER_OWN output value is TRUE. An alarm is generated if the tap changer
does not move downwards in Cmd error delay time after the pulse activation,
assuming that the own tap changer position is connected.
In the second case, the parameters are set so that the value of Lower block tap exceeds
the value of Raise block tap. The raising control activates the RAISE_OWN output.
The result should be that the tap changer lowers its position and the measured voltage
rises. Furthermore, the RAISE_OWN output value is TRUE in the 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,
resulting that ALARM_REAS in the monitored data contains a command error value.
The lowering control works in a similar way, as shown in
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.

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 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 secondary voltage 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
control voltage is the desired transformer secondary voltage to be maintained by the
1MRS759142 C
Figure 812. In the output
Figure 812. In the output
Equation 338. Hence, the
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