Transformer switching inrush current and harmonics

EAF transformer switching on inrush current and harmonics

Transformer switching inrush current and harmonics: The Power System measurements were carried-out at 33kv primary bus, across a 150mva, 33kv/1120v, Electrical Arc Furnace Transformer, supplying to a 180 Ton EAF Furnace, connecting through a set of 2nos. 2000A, 33kv, in parallel, SF6 Circuit Breakers. The captured current waveforms and harmonics bar graph, as shown in the caption picture above, is a rarity since it is shot/recorded at the same microsecond/ millisecond instant of a transformer switching ON.

Transformer switching on current & voltage waveforms
Transformer switching V&I waveforms

It pertains to a NO-LOAD TRANSFORMER SWITCHING ON, CURRENT WAVEFORMS, AND HARMONICS. The EAF Transformer rating was 150mva, 33kv/1120v, and it was for a 180ton AC Electric Arc Furnace application. Further the continuous waveform graph after its switching ON, as shown in the picture below for about 10cycles, depicts a normal Transformer Switching Characteristics, while No-Load charging.