ABB TCC300, User Manual, Page: 532 / 716

The directional operation of the control will be reversed whenever the power flow reverses
to as little as 2% (4 mA) of the nominal 200 mA rating of the control. For example, to
change from a normal forward power to reverse operation, 4 mA of the real component of
the load current must be detected in the reverse direction. To then revert back to the normal
forward direction operation, 4 mA of the real component must be detected in the forward
direction. This establishes an 8 mA "hysteresis" effect.
Additionally, the control can be "biased" in either the forward or reverse direction
depending on circuit or system configuration. This essentially removes the 2%
requirement from the change to the biased direction. For example, a control biased in the
forward direction will change to the reverse direction as described above. It will require
only that the power flow be in the forward direction to change back to forward operation.
This biasing reduces the "hysteresis" effect to 4 mA from the original 8 mA.
In order for the "regulate in reverse direction" or "return to the neutral position" to
implement properly, two prerequisites are required. The first is Tap Position Knowledge.
Without knowledge of the tap position it would be impossible for the control to run the
tapchanger to the neutral position. The second is source side voltage. Without knowledge
of the source side voltage, it would be impossible to regulate it.
Detecting Reverse Power
Reverse power flow exists whenever the real component of the load current changes
direction from forward and remains until another reversal to forward power flow occurs.
The control reliably determines power direction with as little as 2% of the real component
of the nominal 200 mA load current (4.0 mA). A LED on the front panel will illuminate
whenever the control senses a reverse power condition.
Power Direction Bias Setpoints
Power Direction Bias includes three settings to determine how the control will switch
between forward and reverse power operation. The three settings are None, Forward Bias,
and Reverse Bias.
Section 7
1VAC388793-MB A
Setpoints
526 TCC300
User Manual