Magnetizing Current, Harmonic Content and Power Factor as the Indicators of Transformer Core Saturation

Abstract

Abstract-The paper proposes a measurement method for obtaining the parameters needed to calculate a reliable indicator of the state of transformer core saturation. The major nonlinear effects in transformer core are saturation, eddy current and hysteresis. Saturation is the predominant effect in power transformers, followed by eddy current and hysteresis effects. In saturation, a transformer core act as a source of current generating harmonics, some of which will flow directly toward the primary and secondary windings. The method is based on magnetization current, harmonic content and power factor evaluated of the transformer no-load current with high magnetic flux density subjected. The investigation is done on single phase model core type transformer. The transformer is connected to variable voltage variable frequency (VVVF) source and the investigation is done on various flux densities. The results show that the magnetization current and harmonic content increase significantly when high magnetic flux densities are injected and vice versa with power factor that decrease sharply. These phenomena can be used as the indication of transformer core saturation.

Analysis of Magnetization Currents

“…The waveforms observed are quite similar. Such curves are typical for circuits with magnetic hysteresis [1,2,5,6]. …”

“…The hysteresis leads to the appearance of the harmonics in the transformer current. This phenomenon is widely discussed in current publications [5][6][7], emphasizing the importance of the problem.…”

“…The shape of the transformer magnetization current may be evaluated by numerical calculations as presented in [5,6]. In addition, the influence of the flux density on the harmonic current contents is discussed in [6].…”

“…In addition, the influence of the flux density on the harmonic current contents is discussed in [6]. The improved model of the transformer protection system is developed by changing the magnetization current spectrum [7].…”

Analysis Magnetization Current of Harmonic Phenomena and Power Factor as Indicators of Core Saturation at Transformer 3-Phase

“…By the standards of IEC (International Electro technical Commissioning) 1000.4 -11, they're classified into harmonic interference waveform distortion [2] [3]. In this phenomenon changes the waveform of the wave base.…”