The properties of the used tap changer are set in the tap settings. They allow for the configuration of
the number of tap changer positions, the middle position, and the position indication message. There
are several different ways to connect tap position indication:
• mA input cards installed to the AQ-200 unit
• External mA input units (ADAM-4016) connected to AQ-200 units RS-485 serial port
• Binary coded inputs (with digital inputs)
• BCD coded inputs (with digital inputs)
• Measuring resistance with RTD channel
• Measuring voltage with a digital input
Setting up tap position indication for all of the above mentioned options are described below.
mA input
For example, let us say a transformer has a tap changer with 18 positions, with position 9 presenting
the middle position. The tap changer location is indicated by the mA signal (4…20 mA). Each tap
position has a 1.67 % effect on the transformer's output voltage. The highest mA value is expected
when the tap is in the highest position.
According to these data, the tap changer properties are set to the AVR as follows:
Setting
Value
Tap position indication
mA input
Tap steps totally
18 steps
Tap center position
9 step
Tap step effect
1.67 %
mA input low range
4 mA
mA input high range
20 mA
Tap position indication
Max.mA.max.Pos
Based on these given values, the AVR function calculates the following:
Calculation
Value
Tap step voltage effect
334 V
pri
Tap maximum decrease
-15.03 %
Tap maximum increase
15.03 %
Tap control band
30.06 %
Tap step in mA
0.889 mA
mA input now
measured mA input value
These basic settings define the control area where the AVR must operate.
Either Channel 1 or 2 can be used to connect a mA input to an option card (see the image below).
A
AQ
Q-T215
-T215
Instruction manual
Version: 2.04
264
