变压器油纸绝缘状态的频域介电谱特征参量及评估方法

Characteristic Parameters and Assessment Methods of Frequency-Domain Dielectric Spectroscopy of Oil-Paper Insulation for Transformers

为了区分水分和老化产物对油纸绝缘频域介电特性的影响,进一步将频域介电谱测试方法更好地应用于评估变压器主绝缘的老化状态,本文在实验室中获得了不同水分含量及老化程度油纸绝缘试品的频域介电谱特性曲线,通过分析其变化规律,提出一种采用不同测试频率点对应介质损耗正切tan?为特征参量,以区分水分和老化状态影响的评估方法,并初步给出了各参量与水分含量和老化状态的定量拟合公式。结果表明,tan?在10?3~102Hz范围内随油纸绝缘水分含量增加而增大,而老化程度增加仅影响其在10?3~10?1Hz范围内的值;不同频率点对应的tan?值与水分含量和绝缘纸聚合度的拟合曲线呈现指数函数关系。应用该研究方法对一台现场运行的电力变压器主绝缘绝缘纸的水分含量和聚合度值进行评估,初步验证了该方法的有效性。

In order to apply the technology of frequency-domain dielectric spectroscopy(FDS) to assess the aging condition of the main insulation of transformer more accurately, the method of distinguishing the influence of moisture content and aging product on the dielectric property of oil-paper insulation in frequency domain is investigated in this paper. FDS properties of oil-paper insulation with different moisture contents and aging degrees are measured in laboratory under controllable condition. The loss factors tan? corresponding to different measurement frequency points are proposed as characteristics to distinguish the influences of moisture contents and aging degrees. The quantitative relationships between the characteristics and the moisture content or aging degree are initially proposed. The results show that in the range of 10?3 to 102 Hz, tan? increases with the increase of moisture content, while the aging degree only affects the value of tan? in the range of 10?3 to 10?1Hz; An exponential rule is observed in the relation between the tan? at different frequency points and moisture content as well as the degree of polymerization(KDP) of the insulation paper. A preliminary validity of the proposed method is verified by applying it to a power transformer in service to evaluate the moisture content and KDP of its main insulation paper.