Analysis on 500 kV Power Transformer Vibration Under DC Magnetic Biasing

Combined with vibration tests of power transforemers in two 500 kV substations,the vibration mechanism of high-capacity power transmformer under DC magnetic biasing is analyzed and the vibration characteristics are extracted.Firstly,based on the principle of transformer vibration and magnetic biasing the mechanism of transformer vibration under DC magnetic biasing is analyzed and two half-period waveforms within a power frequency period are obtained,the obtained waveforms possess three features: the main feature is the obvious energy discrepancy between the two waveforms and the rest of the features are the increase of the power of high frequency components in the signal and the increase of signal complexity;secondly,suitable signal feature extraction methods are proposed to obtain the features of vibration caused by magnetic biasing;finally,the spectrum analysis and feature extraction analysis of transformer vibration signals,which are caused by geo-magnetically induced current(GIC),that is obtained by screening DC component of neutral point current combined with horizontal component of geomagnetism,or by monopole operation of HVDC power transmission are perfomed.Analysis results show that the proposed DC magnetic biasing features and corresponding feature extraction methods are effective.