Suppose we dont know the vector group of transformer, how to check its vector group through test? I have 3 transformer DYn11 %26amp; DYno%26amp; Ynd11, how to confirm its vector group?|||Dissolved Gas Analysis (DGA) is a proven and
meaningful method. If increased levels of
hydrocarbon gases are found in the oil, the fault
must be located as soon as possible. Hence
important preventative maintenance must be
performed in time to avoid an unexpected
total failure.
The most frequent
sources of faults are the tap changers, bushings,
the paper-oil insulation and the accessory
equipment.
In order to find the source and reason for
high gas values, further tests have to be
performed on the transformer. Common test
methods are:
l Turns ratio, vector group and excitation
current measurement
l Static winding resistance measurement
l Dynamic winding resistance measurement
to test the on-load tap changer (OLTC)
l Sweep frequency response analysis
(SFRA) measurement
l Frequency dependant capacitance and
dissipation factor measurement
l Di-electric response analysis
l Partial discharge (PD) measurement
Turns ratio, vector group and excitation
current measurement
The transformer turns ratio test (TTR) is performed
by applying a test voltage (typically 500 V
L-L) to the HV winding of a transformer and
measuring the LV voltage. The test can either
be performed as single-phase or threephase
and typically is performed for each
tap step of a tap-changer. In the case of
a three-phase injection and if testing a YD
or DY transformer, the injected or measured
voltage on the delta winding needs to be
adjusted by a factor of 鈭?.
The vector group test (VG) is performed in a
very similar fashion as the TTR test 鈥?except
that it is performed by injecting a balanced
three phase voltage, i.e. this test is not
possible with a single phase injection.
http://www.eepublishers.co.za/images/upl鈥?/a>
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