並列変圧器投入時の6%直列リアクトル付コンデンサの過電流トリップ現象

抄録

This paper discusses the harmonic distortion occurring at capacitors with 6% series reactor upon energization of parallel connected 3-winding transformer. The harmonic order of resonance between the capacitor and the 6% series reactor is 4.1th harmonic, which is fairly close to the 4th harmonic. Energizing a transformer on the power system can cause sympathetic magnetizing inrush currents to flow in an already energized parallel transformer. Energizing the second transformer causes a voltage drop across the resistance of the source line feeding the transformers. This voltage drop may cause a saturation of the already energized transformer in the negative direction. This saturation causes magnetizing inrush current to supply the flux. This sympathetic inrush current through inductive reactance associated with the source line and leakage reactance of the already energized transformer causes voltage distortion at the load side (capacitor circuit). As the 4th harmonic of the voltage becomes larger, the 4.1th harmonic resonance between the power capacitor and the 6% series reactor occurs, and huge current instantaneously flows. EMTP (Electro Magnetic Transients Program) simulation of the energization of parallel connected transformer (sympathetic inrush) was carried out. As a result, the waveforms simulated by EMTP reproduced the measured waveforms.