直流偏磁对 500 kV 变压器振动特性的影响分析

Under the monopole-ground operation mode of ultra-high voltage direct current （UHVDC） transmission project，the direct current（DC） intrudes into the winding of large power transformer，causing vibration of transformer to intensify. In order to deeply understand the influence of DC bias on the vibration characteristics of large power transformer，the vibration mechanism of transformers and the influence of DC bias are analyzed. During the system commissioning of Baihetan-Jiangsu ±800 kV UHVDC power transmission project，the neutral current and vibration signals of 500 kV three-phase transformer are measured，the DC bias degree is quantified，and the time-domain and frequency spectrum characteristics of vibration signal under different DC bias degrees are analyzed. The waveform distortion ratio，odd-even harmonic energy ratio，cumulative energy ratio and power spectrum entropy are extracted to analyze the influence of DC bias on the vibration characteristics of large power transformer. The results show that DC bias leads to waveform distortion and the vibration waveforms of two half-period waveforms within a power frequency period are no longer distributed symmetrically. With the increase of DC bias degree，the main frequency components of vibration signal change，and the 50 Hz doubling components gradually increase，among which the odd harmonic components increase more than the even harmonic components，and the influence is mainly concentrated within 600 Hz. Due to the saturation effect of the iron core，when the DC bias increases to a certain extent，the magnetic unbalance decreases and the complexity of vibration signals no longer increases.