非标准冲击电压对油纸绝缘放电特性和累积效应的影响

The double exponential waveforms recommended by the IEC standard significantly differ from the actual over-voltage waveforms that invade power transformers. The influence of such difference on the failure characteristics of oil paper insulation still remains unclear. Meanwhile, during the decades-long operation, millions of impulses invade power transformer. Its influence rules and mechanisms on the oil paper insulation needs further study. The above factors would affect the insulation design, protection and safe operation of power transformer. Based on the overvoltage statistical data, this project studies the difference in failure characteristics under both non-standard impulse voltages and double exponential impulse voltages. A waveform equivalence method is proposed based on probability quality analysis of the failure data. By revealing the space-time behavior of space charges in the dielectric under repeated impulse voltage, we expect to analyze the significant effect of space charges on the accumulative failure. In this project, we plan to determine the dynamic evolution of micro structure, dielectric properties and accumulative damage resultant spectrum in the oil paper insulation. Combining the molecular dynamics model for dynamic damage of dielectrics, we expect to reveal the accumulative failure mechanism of dielectrics and the influence of waveform difference on the accumulative damage characteristics. The implementation of this project can provide an important theoretical basis for the optimization of insulation structure and safe operation of electrical apparatus.

运行变压器实际侵入的冲击电压波与IEC推荐的双指数冲击电压波波形存在显著差异，两种波形对油纸绝缘失效特性影响的差异性尚不明确，同时变压器在寿命周期内会承受数万次冲击电压的累积作用，其对油纸绝缘的影响规律和作用机制仍不清楚，这些问题给变压器的绝缘设计、防护、安全运行埋下隐患。本项目在实测过电压统计数据的基础上，研究非标准振荡波与双指数波作用下油纸绝缘失效特性的差异性规律，通过对失效特性数据的偏差概率分析，提出两种波的等效方法；通过研究冲击电压累积作用下介质内空间电荷的多时空尺度行为特征，建立空间电荷特性-累积效应特征参量高维模型，分析两种波形作用下空间电荷对介质累积失效过程的影响和差异；挖掘介质在冲击电压累积作用下微观结构、介电特征和损伤生成物谱的演变规律，建立介质动态损伤分子动力学模型，揭示介质累积失效的机制以及波形差异对累积损伤特性的影响规律，为变压器绝缘结构优化和安全运行提供理论依据。

运行变压器实际侵入的冲击电压波与IEC推荐的双指数冲击电压波波形存在显著差异，两种波形对油纸绝缘失效特性影响的差异性尚不明确，同时变压器在寿命周期内会承受数万次冲击电压的累积作用，其对油纸绝缘的影响规律和作用机制仍不清楚，这些问题给变压器的绝缘设计、防护、安全运行埋下隐患。本项目针对实际非标准暂态电压下油纸绝缘累积失效的问题开展研究，得到了不同波形参数双指数波/振荡衰减波作用下油纸绝缘的击穿特性与累积失效规律，揭示了作用电压波形特征参量与绝缘介质失效特性之间的关联关系，并基于大量试验数据建立了电压-梯度二维约束的非标准冲击电压波形等价体系；试验研究了冲击电压累积作用下油纸绝缘内空间电荷的演化规律与陷阱分布特征，通过建立双极性电荷输运模型以及固体介质微观束缚态电子的振动与脱陷模型，揭示了冲击电压波形特征参量与介质失效特性之间的关联关系；成功制备了纳米二氧化钛改性变压器油浸渍绝缘纸以及纳米氧化铝改性纤维素纸，实现油纸绝缘耐受冲击电压累积效应与电气性能的大幅度提升。