Measurement of magnetic fields within a 3-phase core-type transformer during the positive- and zero-sequence impedance tests

This paper shows the measured magnetic fields in a 3-phase core-type transformer (5MVA, YNyn, with and without tank) during the positive- and zero-sequence impedance tests. The magnetic fields were measured in different points of the non-ferromagnetic region, for 10 different test conditions. For each measured point, the magnetic fields were measured in the three Cartesian axes of the space. The results are the maps of magnetic field distribution for each measured condition. The following topics are analyzed: a) tank effect; b) differences between positive- and zero-sequence cases; c) differences between the diverse zero-sequence tests.