变压器油中微水的激光散射测量技术

Laser Scattering Measurement Technology of Micro-water in Transformer Oil

变压器油中微水是影响绝缘性能的重要因素,为了克服现有检测方法稳定性差、主观性强、使用条件严苛等不足,通过数字图像量化波长为650 nm的激光在油中形成的散射光柱灰度,结合米氏散射和瑞利散射理论特征,利用光强衰减、区间灰度像素统计等手段对比了变压器油的温度、颗粒度和微水含量(水分质量分数)等数据。研究发现:散射光强与微水颗粒的尺寸之间的关系为主导关系,但会受到油温度、颗粒度的干扰;油中温度升高会促使微水含量≤10×10^(−6)的微水颗粒合并为主导,而当微水含量(水分质量分数)>10×10^(−6)时,微水颗粒分解和合并逐渐达到平衡;油微水与光柱呈现明显的指数关系,通过调节数字图像灰度的敏感度,增加像素统计量匹配不同区间微水,可以降低数值波动,并给出了颗粒度和温度线性校准的实例。研究结果表明,所提方法能够实现变压器油中微水含量的测量,可用于油浸式变压器的油中微水检测。

The micro-water in transformer oil is an important factor that affects the insulation performance.In order to overcome the shortcomings of existing detection methods,such as poor stability,strong subjectivity and harsh use condi-tions.The gray level of the scattering light column formed by the 650 nm laser in the oil is quantified by digital image,combined with the theoretical characteristics of Mie scattering and Rayleigh scattering.The temperature,particle size and micro-water content of transformer oil are compared by means of light intensity attenuation and interval gray pixel statis-tics.It is found that the scattering light intensity is mainly related to the size of micro-water particles,but it is affected by oil temperature and particle size.The increase of temperature in the oil will promote the combination of micro-water par-ticles with micro-water content less than or equal to 10×10^(−6)(mass fraction)to be dominant,while when the micro-water content is larger than 10×10^(−6)(mass fraction),the decomposition and combination of micro-water particles will gradually reach a balance.The oil micro-water and the light column show obvious an exponential relationship.By adjusting the sensitivity of the digital image gray level to increase the pixel statistics to match the micro-water in different regions,the numerical fluctuation can be reduced.An example of linear calibration of particle size and temperature is given.The re-search results show that this method can be adopted to realize the measurement of micro-water content in transformer oil and can be used for the detection of micro-water in oil of oil-immersed transformer.