绝缘纸板干燥过程微水分检测机理与试验

Mechanisms of Moisture Content Measurement of Transformer Pressboard

绝缘纸板中的微水分对电力变压器的使用寿命有严重影响,因此,实时精确监测绝缘纸板微水分含量对于电力变压器的生产具有重要意义。由于绝缘纸板微水分含量的变化必然引起材料介电性能的变化,对介电性能进行检测即可有效检测微水分含量的变化。文中采用边缘场电容传感器技术研究绝缘纸板介电性能的变化过程。分析了频率对电容传感器检测信号的影响因素。通过对绝缘纸板的介电极化和介电损耗的研究,提出了频率对电信号影响的理论模型。根据试验数据和介电谱曲线,建立了无油绝缘纸板内的水分质量分数与复介电常数关系的数学模型。

The presence of moisture in transformer pressboard has a detrimental effect on insulation life.It is important to have the capability of accurately measuring and monitoring the moisture of pressboard for the manufacture of power transformer industry.The dielectric properties of pressboard play an essential role in evaluating the moisture concentration since the moisture affects the dielectric properties of pressboard.The fringing electric field sensor was used to monitor the dielectric response of the insulation in real-time.The effects of frequency to the signal of capacitive sensor were analyzed.A model of effects of frequency on signal was developed with studying of the dielectric polarization and loss of pressboard.A calibrated expression relating permittivity and moisture content of oil-free pressboard is presented by using experiment data and dielectric frequency spectra.