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The ΔVAR2 Method is incorporated in the ABB TCC300 Tapchanger Control, as an
option. This option internally calculates and compares the individual transformer VAr
flows. Decisions for voltage setpoint biasing are then made and implemented to change
tap positions in such a manner that the difference in VAr flow is minimized.
Action is taken continuously as the MVAr load is changing such that the magnitude of
difference in VAr loading is minimized (depending on the VAr difference of one, off-
optimum, tap position).
The use of LDC (line drop compensation) is precluded when ΔVAR2 is used since no
provision is made for the increase in load currents in one transformer when the other is out
of service. The result would be doubling the LDC effect when in independent operation.
6.3.1.3 ΔVAR2 connection
As shown in Figure 332 , the current input is connected to the load current terminals of the
control and then into the circulating current terminals (Ip) of the paralleled transformer
control. Each control now sees the same voltage and each transformer current separately.
This allows each control to calculate the VAr flows in both transformers for comparison,
without externally sorting out the load and circulating current values. Breaker contact
52
‑
3b is used to signal theTCC300 Control to disable paralleling using the neutral light
input (Redefined when ΔVAR2 selected). An external independent/parallel switch (43P)
is suggested to provide manual control for testing and maintenance. The effectiveness of
this grounding is important for the recognition of this condition.
1VAC388793-MB A
Section 6
Configuration
TCC300 405
User Manual