Sweep Frequency Response Analyzer (SFRA) User Guide
B-2 72A-2570-01 Rev. K 07/2011
• LTC position. Changing LTC affects SFRA response. Before you
move the tap changer into neutral position, record the previous tap
position so that you can identify possible influences from the LTC
reversing switch.
• DETC position. Transformers in service occasionally have problems
due to DETC movement. Doble does not recommend altering the
DETC position for an SFRA test. The exception is in factory tests on a
new transformer, where it can be assumed that the DETC is in
operating condition and tests can be performed on nominal tap.
Two-Winding Transformers
* Indicates short-circuit tests where the terminals are shorted together with three
sets of jumpers, to provide symmetry (X1-X2, X2-X3, X3-X1) OR (Y1-Y2,
Y2-Y3, Y3-Y1). The neutral is not included for 3 wye connections, but may
be included for 1 test connections.
Table B.1 Two-Winding Transformers — 9 Tests
Test Type Test #
3
Delta-
Wye
3
Wye-
Delta
3
Delta-
Delta
3
Wye-
Wye 1
HV Open Circuit
(OC)
All Other Terminals
Floating
Test 1 H1-H3 H1-H0 H1-H3 H1-H0 H1-H2(H0)
Test 2 H2-H1 H2-H0 H2-H1 H2-H0
Test 3 H3-H2 H3-H0 H3-H2 H3-H0
LV Open Circuit
(OC)
All Other Terminals
Floating
Test 4 X1-X0 X1-X3 X1-X3 X1-X0 X1-X2(X0)
Test 5 X2-X0 X2-X1 X2-X1 X2-X0
Test 6 X3-X0 X3-X2 X3-X2 X3-X0
Short Circuit (SC)
High (H) to Low (L)
Short [X1-X2-X3]*
Test 7 H1-H3 H1-H0 H1-H3 H1-H0 H1-H2(H0)
Short
X1-X2(X0)*
Test 8 H2-H1 H2-H0 H2-H1 H2-H0
Test 9 H3-H2 H3-H0 H3-H2 H3-H0
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