直流偏磁下500kV单相变压器振动噪声的试验研究

Experiment on Vibro-Acoustic Characteristic of 500kV Single-Phase Transformer under DC-Bias

直流偏磁是电力变压器的一种非正常工作状态,直流流入变压器后将在铁心中产生直流磁通,导致变压器铁心出现半波饱和、励磁电流严重畸变、局部过热、振动噪声增加等一系列问题,并且大容量单相自耦变压器更易受到直流偏磁的影响,对电网的安全稳定运行产生了严重的威胁。该文利用两台参数一致的250MV·A/500kV变压器分别进行了空载和负载直流偏磁试验,对变压器直流偏磁下的电压畸变率、励磁电流、振动和噪声进行测量,并分析研究其直流偏磁下的变化趋势、分布规律和频谱特征。试验结果为大型变压器在实际运行情况下的直流偏磁耐受能力评估及直流偏磁下的振动噪声特性研究提供参考依据。

DC bias is an abnormal working state of transformer.The main effect of a DC current flowing into a transformer winding is the half-cycle magnetic core saturation,as a result,a series of problems occur,such as the serious distortion of excitation current,partial overheating and increase of vibro-acoustic noise.The big capacity single-phase autotransformer has less tolerance to the DC bias current,which have a serious threat to the safe and stable operation of the power grid.In this paper,two identical 250MV·A/500kV transformers are used for DC bias experiments with and without load.The voltage distortion rate,excitation current,vibration and noise under DC bias of the transformer are measured,and the variation,distribution and harmonics spectrum characteristics under DC bias are analyzed.The test results would provide a reference for the assessment of DC endurance capability and the study of vibro-acoustic noise characteristics of large capacity transformers in actual operation.