A dynamic harmonic domain-based framework to detect 3-phase balanced systems under dynamic transients: the test case of inrush current in transformers

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It is well-known that energizing a transformer can cause significant transients and harmonic pollution especially in the first few cycles. The waveforms of the three-phase inrush currents are different even if the transformer is operating in a balanced condition; but analyzing the harmonics of three-phase inrush currents shows that they are completely balanced if the transformer is under a balanced condition. This observation is possible only if the transformer is analyzed by using the dynamic harmonic domain (DHD). The DHD provides dynamic analysis of the harmonics in the transformer from transient period to steady state. In this paper, physical meaning of harmonics during the transient period is also included. Moreover, a concept of three-phase balanced systems under dynamic nonsinusoidal conditions is presented and explained with the inrush current in a three-phase transformer.

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