Turn ratio test is a comparison test of the number of secondary turns with the primary turns on the transformer. The turns ratio and group vector testing in one of the routine transformer tests. The turns ratio and group vector tests can be carried out at the factory or at an electrical substation, This test generally uses the Transformer Turns Ratio (TTR) test tool, the test equipment used sometimes experiences technical and non-technical problems so a comparative test method is needed to get a good analysis. The research method used is observational research, namely analyzing the transformer to be studied by corshucting TTR testing in heo ways, namely testing with test equipment and three-phase low voltage sources, aiming to obtain a very good level of accuracy. The test results were analyzed and compared with theory and calculations, with reference to the IEC 60076-1 standard. The results of the comparison of windings and group vectors using the TTR 100 test equipment and a 3-phase low voltage source (TVR) show the same conclusions as the results of the analysis, where the first transformer sample is is normal condition and meets IEC 60076-1 Standard, while the second sample transformer is in un abnormal condition in the W winding where the difference value is above 0.5%. Based on the MATLAB Simulink simidation that transformers can be parallelized if the group vector, the number of phases and the voltage are the same.

Keywords: Distribution transformer, Vector group, Transformer turns