油浸绝缘纸电劣化过程中的局部放电混沌特性

Chaotic Characteristic of Partial Discharge During Electrical Degradation of Oil-impregnated Paper

为探究油浸绝缘纸板的局部放电(PD)劣化过程,在实验室中进行油浸绝缘纸的局部放电劣化实验。以实际变压器绕组绝缘纸为研究对象,通过加速电劣化实验得到试品的平均击穿时间,拟合出试品电劣化的反幂寿命模型,确定3个实验电压。采用超高频天线采集整个电劣化过程中试品的局部放电信号,并将整个劣化过程划分为10个阶段。最后,采用混沌理论分析局部放电幅值时间序列的最大Lyapunov指数、关联维数以及Komogorov熵等特征参量在油浸绝缘纸电劣化过程中的变化规律。结果表明,随着劣化的持续发展,最大Lyapunov指数不断增大,与油浸绝缘纸电劣化状态具有明显的相关性;关联维数呈一定的波动状态,但在绝缘预击穿阶段有明显下降;劣化初期的局部放电混沌特性最强,但随后迅速下降并在劣化中前期达到最小,之后呈现稳定的小幅度增加。

We performed experiments of partial discharge （PD） induced degradation of oil-impregnated paper in laboratory to investigate the electrical degradation process of oil-impregnated paper caused by PD. Using practical winding insulation papers of transformer as the test object, we obtained the average breakdown time by accelerated electrical degradation experiments to fit the inverse-power-law life model of electrical degradation. Then three testing voltages were determined according to the life model. The electrical degradation process was divided into ten stages, and the PD signals were collected by an ultra-high-frequency antenna throughout the stages. By using the chaos theory, the variation laws of several characteristic features of PD amplitude series, such as the largest Lyapunov exponential, correlation dimension, and Komogorov entropy, were analyzed along with the processing electrical degradation of oil-impregnated paper. It is illustrated that the largest Lyapunov exponent increases with degradation, which is obviously correlated to the degradation condition of oil-impregnated paper. In addition, the correlation dimension shows a certain fluctuation, and it decreases sharply at the pre-breakdown stage. Moreover, the PD chaotic characteristic is the strongest at the initial stage of degradation, rapidly falls into its minimum at the middle stage of degradation, and then increases steadily and slow.