直流电压下变压器油纸绝缘局部放电的发展过程

Partial Discharge Process of Transformer Oil-paper Insulation Under DC Voltage

研究变压器油纸绝缘局部放电(PD)的发展过程对于特高压换流变压器的运行维护十分重要。为此,对典型油纸复合绝缘缺陷模型在直流电压长期(100 h)作用下的局部放电信号进行了统计分析;根据其统计特征图谱,将直流局部放电发展过程划分为4个阶段。此外,还采用无感电阻测量直流局部放电单个脉冲波形;并对直流电压长期作用下的油浸绝缘纸板表面形貌变化进行了观测。试验结果表明,直流电压下的局部放电脉冲的上升沿在10～100 ns范围内,首脉冲持续时间约500 ns,其余振荡脉冲脉宽在600～900 ns范围内;估算得出单次直流放电脉冲能量在0.01～0.1 J范围内。此外,研究发现绝缘纸板的表面会在针电极电蚀作用下产生"凹坑",这为实现基于多信息融合的直流局部放电发展趋势预测奠定了基础。

Understanding the development of partial discharge （PD） in oil-paper insulation of transformers is essential for the operation and maintenance of UHV converter transformers. Therefore, we statistically investigated the PD signals of typical oil-paper insulation defect model under DC voltage for 100 hours. According to the obtained time-resolved pat- terns of pulse sequence, PD process could be divided into four stages. Moreover, we measured single pulse waveforms of DC PD by using senseless resistor, and observed the varying surface morphology of oil-insulated cardboard influenced by DC voltage in a long period. According to the investigation, rise time of PD pulses under DC voltage ranges from 10 ns to 100 ns; the first pulse lasts about 500 ns, and the other pulses＇ width ranges from 600 ns to 900 ns; it is estimated that a single DC PD pulse has energy ranged from 0.01 J to 0.1 J. In addition, it is found that there are ＂holes＂ generated on the surface of insulation cardboard caused by galvanic action from needle electrodes, providing a technical support for fore- casting DC PD development trend based on multi-information fusion systems.