Procedure of transformer vector group test

Vector group test of transformer is done for detecting the vector group. These tests are done when the tap of transformer is nominal. One procedure of Vector group testing of transformer is explained as below: First, connect the test power supply to high voltage winding. Secondly, connect a2 and A2 terminals to each other in order to make one common point between secondary and primary sections. Finally, by measuring the voltages between all terminals and drawing the corresponded plots, the value of vector group is achieved.While performing the tests, if there is a neutral wire, this wire should not be connected to earth to prevent creation of the eddy current. If the auto-transformer has the triangle Tertiary winding, electrical connection should be created between the winding and the high voltage section.


Calculating the value of vector group

One simple procedure for calculating the vector group: For finding vector group, assume the high voltage vector on minute pointer and consider it along 12: 00 o’clock.Assume Low voltage vector on hour pointer. Each hour is equivalent to 30 degree of phase difference between Synonymous phases. If the phase difference value is divided to 30, the resulting value is vector group. For example, in below picture, the value of vector group is 4.



Type of transformer connections

According to IEC-76-4, the value of vector group can be 0,1,2,4,5,6,7,8,10,11. Mainly, the type of transformer connections are divided in 4 below groups: 1)Transformer with 0,4 or 8 vector group values2)Transformers with 2,6 or 10 vector group values 3)Transformer with 1 or 5 vector group values 4)Transformer with 7 or 11 vector group values

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