Induced voltage test of distribution transformers using static frequency inverters

In high voltage systems, conventional method of generating a wave with a frequency over 50 Hz that has high power is interconnecting a motor and a generator with nominal frequency over 50 Hz, like 100 Hz or 150 Hz; but for routine test of distribution transformers, it is not economical to construct a experimental setup with a motor and generator. Nowadays with power electronics instruments some cheap solutions are available, like power frequency inverters that transmit power from the 50 Hz network to over 50 Hz sinusoidal wave as output. This paper reviews a procedure of design and construction a test circuit for induced voltage tests, loss measurements and applied voltage tests based according to IEC 60076-3, based on a three phase power frequency inverter with the frequency in the range of 0-200 Hz. This system strongly needs a compensation unit, adaptation transformer, and a HV passive filter for the induced voltage tests. The compensation unit used in this test set up consists of a number of inductors and capacitors connected in a pi circuit, so it was possible to achieve a total harmonic distortion less than 2%.