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• The DVAR current on Transformer 1 is Leading
• The DVAR current on Transformers 2 and 3 is Lagging
• The DVAR current on Transformer 1 will have twice the magnitude of
Transformers 2 and 3, and they should both have the same magnitude.
• The DVAR current on Transformers 2 and 3 should have the same magnitude.
Since Transformers 2 and 3 will be supplying all the load, their voltage may
decrease. Transformer 1 voltage may increase since it has no load (if its PT is
between the breaker and the transformer).
38. Open the Low Side Breaker for Transformer 1 and verify that the controls are not
calling for any tap change operations.
The load current on Transformers 2 and 3 should have changed from one third to one
half and Transformer 1 load should be at or near zero.
39. Verify that the DVAR current on Transformer 1 is at or near zero.
40. If necessary, manually initiate tap change operations to bring the voltage back into
band.
41. Manually raise Transformer 2, one tap.
42. Verify the following:
• The DVAR current on Transformer 2 is lagging
• The DVAR current on Transformer 3 is leading
• The DVAR current on Transformers 2 and 3 have the same magnitude
• The DVAR current on Transformer 1 should be at or near zero
43. Manually place the transformers to the same tap position (or the same difference as
noted above).
44. Close the Low Side Breaker for Transformer 1 and verify that the DVAR current in
all the transformers is at or near zero.
Assuming all the transformers are the same and the high side sources are all
connected together, only one high side source for the paralleled transformers. If the
high side is not connected together then it may be necessary to adjust the tap
positions to achieve zero DVAR current or the minimum value possible.
45. Manually Lower Transformer 2, one or two taps.
46. Manually Raise Transformers 1 and 3, one or two taps.
The regulated voltage should still be in band near the center of the band width.
47. Verify the following:
• The DVAR current on Transformer 2 is leading
• The DVAR current on Transformers 1 and 3 is lagging
• The DVAR current on Transformer 2 will have twice the magnitude of
Transformers 1 and 3
• The DVAR current on Transformers 1 and 3 should have the same magnitude
Since Transformers 1 and 3 will be supplying all the load, their voltage may
decrease. Transformer 2 voltage may increase since it has no load (if its PT is
between the breaker and the transformer).
1VAC388793-MB A
Section 9
Testing
TCC300 591
User Manual