tap and lowering Transformers 2 and 3 one tap until all controls are calling for the
correct operation.
This keeps the regulated voltage near the center of the bandcenter setting and
therefore any operations by the controls will be caused by the DVAR current.
12. Simultaneously place all transformers into Automatic operation and observe where
the transformers stop initiating tap changes.
The transformers should be on the same tap or one tap part, with the controls not
calling for any operations. If the high side is not connected then the tap positions
should be the same number of taps apart as noted above.
13. Place Transformers 1, 2 and 3 in Manual.
14. Raise Transformer 1, one tap to generate some DVAR current.
The transformer with the high voltage (typically the higher tap) will have the lagging
DVAR current and the other two transformers will have the same magnitude but will
indicate a leading DVAR current.
If the load is not evenly distributed between the transformers, then
the voltage on the transformer with the larger load may decrease and
the control may call for a raise. The voltage on the transformer with
the smaller load may increase and its control may call for a lower.
15. Open the Tie Breaker between Transformer 1 and Transformer 2 with Transformer
3 still connected to Transformer 2.
16. Verify that the controls are not calling for any tap change operations.
The load current does not ha ve to be the same when the Tie Breaker opens and the
voltage may change based on the loading of the transformers.
17. Verify that Transformer 1 DVAR current is at or near zero.
18. If necessary, manually initiate tap change operations to bring the voltage back into
band.
19. Verify that Transformer 2 and 3 DVAR current is at or near zero (because they are
on the same tap position).
20. Raise Transformer 2, one tap and verify the following:
•
DVAR current on Transformer 2 is lagging
•
Transformers 3 DVAR current is leading
•
The magnitude of the DVAR Current on Transformer 2 and 3 should be the
same
•
Transformer 1 DVAR current should be at or near zero
21. Manually place all transformers to the same tap position (or the same difference as
noted above).
22. Close the Tie Breaker between Transformer 1 and Transformer 2 and verify that the
DVAR current in all transformers is at or near zero.
Assuming all the transformers are the same tap and the high side sources are all
connected together, only one high side source for the paralleled transformers. If the
1VAC388793-MB A
Section 9
Testing
TCC300
589
User Manual
Summary of Contents for TCC300
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