高频电热应力下环氧树脂绝缘老化特性与寿命评估

发布时间：2019-01-30 21:06

【摘要】：电力电子变压器是一种新型智能变压器,具有一次、二次侧电能灵活传输变换的特点,能满足现代和未来电力系统的很多新要求,其安全可靠运行是电网稳定运行的重要保障。电力电子变压器绝缘长期承受高频电应力和热应力等因子的综合作用,运行环境恶劣,容易发生绝缘的过早失效,其破坏机理较传统的工频正弦模式更为复杂。因此,本文在工频下绝缘材料老化研究的基础上,以环氧树脂绝缘为对象,详细研究了高频电热联合作用下绝缘老化失效问题,为揭示高频应力作用机理和提高电力电子变压器的运行可靠性奠定基础。文中构建了一套高频正弦电压的绝缘老化实验装置,模拟电力电子变压器对绝缘材料进行老化实验。并设计了一套由高频电流传感器和示波器等构成的局部放电检测装置。根据实际测量信号特征,研究了局部放电信号的提取方法。具体包括：首先,构造FIR高通滤波器滤除信号的低频干扰,并利用小波变换方法进行信号分解、阈值降噪和信号重构处理,以滤除高频噪声干扰；然后,通过选取合适的时间窗长度获取有效的放电信号。为研究电力电子变压器绝缘的老化特性,开展了高频绝缘老化试验,并基于局部放电的发展变化规律,从各个不同老化阶段中提取出局部放电特征参量,以分析绝缘高频老化特征及其老化表征参量。研究结果表明,高频电压作用下局部放电相位分布超过90°,相位分布谱图中容易出现“兔耳状”和“三角状”放电。局部放电相位和偏斜度能反应绝缘老化程度,随着老化时间的增大,放电相位向两端扩展,偏斜度逐渐减小。采用加速老化实验方法,开展了大量的寿命实验,计算绝缘材料在各工况下的Weibull统计特征寿命值。通过最小二乘法拟合寿命数据,分析了单因子老化寿命模型。研究结果表明,电压幅值与老化寿命呈指数衰减关系,电压频率和温度与老化寿命呈幂函数衰减关系。并根据多元统计分析方法,构建了多因子作用下的绝缘老化寿命评估模型。
[Abstract]:Power electronic transformer is a new type of intelligent transformer. It can meet many new requirements of modern and future power system with the characteristics of flexible transmission and transformation of primary and secondary side power. Its safe and reliable operation is an important guarantee for the stable operation of power network. The insulation of power electronic transformer is subjected to the comprehensive action of high frequency electric stress and thermal stress for a long time, and its operating environment is bad, so it is prone to premature failure of insulation, and its failure mechanism is more complex than the traditional power frequency sinusoidal mode. Therefore, on the basis of the study on aging of insulation materials at power frequency, the aging failure of insulation under the combined action of high frequency electrothermal treatment was studied in detail, taking the insulation of epoxy resin as the object. It lays a foundation for revealing the mechanism of high frequency stress and improving the reliability of power electronic transformer. In this paper, a high frequency sinusoidal voltage insulation aging test device is constructed to simulate the insulation material aging experiment of power electronic transformer. A set of PD detection device composed of high frequency current sensor and oscilloscope is designed. According to the characteristics of actual measured signals, the extraction method of partial discharge signals is studied. The main contents are as follows: firstly, FIR high-pass filter is constructed to filter the low-frequency interference of the signal, and wavelet transform is used to decompose the signal, reduce the threshold noise and reconstruct the signal to filter the high-frequency noise interference. Then, the effective discharge signal is obtained by selecting the appropriate time window length. In order to study the aging characteristics of insulation in power electronic transformers, high frequency insulation aging tests were carried out. Based on the development and variation of partial discharge, the characteristic parameters of partial discharge were extracted from different aging stages. The high frequency aging characteristics of insulation and its aging characterization parameters were analyzed. The results show that the phase distribution of partial discharge exceeds 90 掳under the action of high frequency voltage, and the "rabbit ear" and "triangle" discharge are easy to appear in the phase distribution spectrum. Partial discharge phase and deflection can reflect the aging degree of insulation. With the increase of aging time, the discharge phase extends to both ends and the deflection decreases gradually. In this paper, a large number of life tests were carried out to calculate the Weibull characteristic life of insulating materials under different working conditions. The single factor aging life model was analyzed by using the least square method to fit the life data. The results show that the voltage amplitude is exponentially attenuated with the aging life, and the voltage frequency and temperature have a power function attenuation relationship with the aging life. According to the multivariate statistical analysis method, a multi-factor model for evaluating the aging life of insulation is constructed.
【学位授予单位】：华北电力大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TM41

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