油纸绝缘加速热老化的频域介电谱特性

Frequency Domain Dielectric Spectroscopy Characteristics of Oil-paper Insulation Under Accelerated Thermal Aging

为研究变压器油纸绝缘不同老化状态及温度对其频域介电谱（frequency domain spectroscopy，FDS）测量结果的影响，对变压器油浸绝缘纸板试品进行加速热老化试验：测量同一试品不同老化阶段10^-3-10^3Hz范围的FDS，并对某一老化状态试品在不同温度下进行FDS测量，分析试品的tanδ、复电容实部C’和虚部C＇＇及微水含量随老化时间和测量时温度的变化。结果表明：随着热老化时问的延长和测量时温度的升高，试品在较低频率下的tanδ和C”逐渐变大，而较高频率下变化不明显，C＇急剧变化的频率区域向高频方向移动；根据FDS测量结果得到的纸板微水含量在老化阶段前期随着老化时间延长明显变大，后期则相对稳定；评估得出的纸板微水含量受温度影响十分明显，温度较高时得到的微水含量明显偏高。

To investigate the impact of aging condition and temperature on the frequency domain spectroscopy （FDS） test results of oil-paper insulation, accelerated thermal aging experiments were performed on oil-impregnated pressboard sample in this work. FDS tests ranging from 1 mHz to 1 kHz were carried out during the aging process, and for the same aging condition, FDS tests were repeated at different temperatures. The variations of dissipation factor （tanδ）, real capacitance （C＇）, imaginary capacitance （C＂） and moisture content caused by aging time and measurement temperature were analyzed. Experimental results show that both tanδ and C＂ of oil-impregnated pressboard increase with the increasing measurement temperature and thermal aging time at lower frequencies, while have no obvious change at higher frequencies. When temperature and thermal aging time increase, the frequency point where C＇ changes rapidly shifts to higher frequencies. The moisture content of pressboard sample obtained from FDS test results increases with the increment of thermal aging time in the earlier stage and shows no obvious change in later stage. The estimated moisture content is also influenced by temperature. When the temperature of sample is higher, the value of estimated moisture content is obviously larger.