doble M4110 - Special Considerations and Test Connections

M4110 Leakage Reactance Interface User Guide
72A-2243-01 Rev. B 9/04 3-3
September 17, 2004
On a new or rebuilt three-phase transformer or during the initial test on a used
transformer, a three-phase equivalent test and per-phase tests should be
performed. This allows comparison with the nameplate value (the three phase
equivalent test), between the phases (per-phase tests) and provides a
benchmark for future tests (per-phase tests). On a single-phase unit, only one
test can be performed (Figure 3.3 M4110 Setup (a)). For comparison, tests
should be performed on the same LTC positions as the nameplate values.
Once the comparison with the nameplate is verified, follow-up tests can
include per-phase tests only. Besides being a more searching test, it allows
comparison not only with the previous test results but between the phases
as well.
The initial tests should be performed on all the de-energized tap changer
positions. It is conceivable that throughout its service life a transformer
may be energized in several DETC positions. When units trip off-line, the
service personnel may be reluctant to change the DETC positions solely to
perform a test in positions in which the initial leakage reactance measurement
was performed
Special Considerations
The test performed from the high-voltage winding at a given voltage requires a
lower current from the source than the test performed at the same voltage from
the low-voltage winding.
It is recommended to perform the test at the highest possible voltage to
minimize the effects of the magnetizing reactance. For further information, see
Proceedings of the Sixty Second Annual International Conference of Doble
Clients, 1995, sec. 8-12.1. When nameplate data is available and input to the
M4000 software, these test settings are selected for you.
For certain winding configurations, the results of the per-phase will not
compare with the nameplate value or results of the three-phase equivalent test.
For further information see Proceedings of the Sixty-Second Annual
International Conference of Doble Clients, 1995, sec. 8-13.1.
Test Connections
Test connections for use with the M4110 are shown in Figure 3.3 M4110
Setup (a) and Figure 3.4 M4110 Setup (b). Test connections for use with
the M4130 are shown in Figure 3.5 M4130 Setup (a) and Figure 3.6 M4130
Setup (b).