This vector group test is done to confirm whether the vector group provided in the name plate is correct or not and also to confirm that the winding has not been damaged during transport, installation and erection.
Taking a particular example, for Dyn11 transformer we have to apply 3~ 400v to the primary, with primary 'U' & secondary 'u' shorted....
then check the voltage across different terminals such as V-v, V-w, W-w, W-v
for Dyn11 configuration (V-v = V-w = W-w)less than W-v....
you can compare the results after drawing the vector diagram for the same......
the purpose of shorting the primary U & secondary u is to nullify the phase shift, to obtain a reference vector...
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Zigzag is the special kind of winding which has both delta and star connection.It has two coils, one coil is connected as a delta and another coil has a star point as Neutral and give to Earth through Neutral earthing resistor.
Procedure of vector group testing:
1. Ensure the system is isolated or not and remove the earthing from the System.
2. Make shot between HV R-Phase and LV R-phase of the Transformer.
3. Apply 3 phase supply to the HV of the Transformer.
4. Measure the combinations of voltages between HV and LV sides compared with the vector diagram.
5. Make sure the combinations are correct or not.
import java.util.Vector; suppose-:::: test t=new test(); /**this is how we add elements to vector*/ Vector v=new Vector(); v.addElements(t);
The open/short-circuit test on a transformer isn't 'needed'. It's only used if you want to find out the efficiency of a transformer.
Back to back test give data for finding the regulation , efficiency and heating under load condition. Back to back test is performed in the presence of two identical transformer. In this test one transformer remains open and other remains loaded. Hence sumpner's back to back test is generalised form of o/c test and s/c test which is performed within one test only. Hence from this test we find core loss and full load copper loss simultaneously at a time.
No. A megger's output voltage is not high enough to test the insulation of a high-voltage transformer if, by 'high-voltage transformer ', you mean a distribution transformer or power transformer. Instead, a high-voltage test set or 'pressure tester' (e.g. a 'HiPot' tester) must be used, as these produce far higher voltages.
there are various types of trasformer tests are here Open Ckt test Short ckt test IR value test Vector group test Phase sequence test Magnetizing test turn ratio test T/f oil insulation breakdown test and so on............