Concerns on electromagnetic compatibility and power quality issues at a three-phase transformer

The paper deals with the behavior of a medium / low voltage transformer (MV/LV), for a non-sinusoidal consumer placed in the transformer's secondary winding. The analysis is performed using the Discrete Wavelet Transform (DWT). The monitoring is realized with two data acquisition systems, briefly described in the paper. Problems associated to the conducted and radiated emissions are addressed and analyzed. Experimental determinations of emissions allowed for the improvement of the quality of performed measurements. Considerations on the determination of some quantities and quality parameters are presented. Electrical quantities are recorded from the MV/LV transformer's primary and secondary windings. The DWT analysis proves that strong non-sinusoidal regimes occur, specifically for the currents in the transformer's windings. The higher order harmonics, not considered in the actual quality standards, can reach high values. These harmonic currents may cause new power quality and respectively Electromagnetic Compatibility problems (including related Electromagnetic Interference problems), not addressed by existing standards (and also unpleasant effects over other equipment from their vicinity).