【作者】 周霏霏；

【导师】 徐岩；

【作者基本信息】 华北电力大学 ， 电力系统及其自动化， 2011， 硕士

【摘要】 研究可靠性更高、性能更完善的变压器主保护原理和算法,在电力系统中既有重要的理论意义,又有很高的实用价值。论文从变压器主保护的“新思路”和“老问题”入手,对目前主保护中尚未彻底解决的难题展开了深入的研究。首次提出了一种基于等效电阻变化特征的变压器主保护新原理。利用瞬时功率的理论和物理含义,定义了端口的等效电阻,从故障的根本性质出发,揭示了变压器发生内部和外部故障状态在本质上的不同,且算法不受励磁涌流、非周期分量、间断角消失、变压器漏阻抗的影响;与差动保护迥然不同的新原理。本文还分析了现有时差法的应用局限性,提出了基于实际电力系统的新型的时差法,利用小波变换提取高频细节和奇异点信息,比较励磁涌流和内部故障电流时差的不同,构成保护判据。本文首次提出了一种基于频谱熵的新型变压器保护原理。在变压器保护中引入频谱熵算法,利用熵的物理意义和发生励磁涌流时固有的两个状态(非饱和阶段和饱和阶段)的转换,研究频谱熵在合闸后第一个周波内的变化情况,构成判据。本文使用基波幅值特征构成了励磁涌流识别的新方法,在TA误差很小的前半个周波内,利用其达到最大值的时间和第一个极大值与最大值之比构成变压器的保护判据。文中提出的变压器保护新判据都经过了大量的动模试验数据验证,试验结果证明了方法的有效性。更多还原

【Abstract】 In the power system, it is of great theoretical significance and high practical value to develop a new transformer protection principle with higher reliability and better performance. This paper makes a study on the transformer protection from two aspects,‘new ideas’and‘old problem’. A new principle based on the equivalent resistance is proposed. Using the theory of instantaneous power, the port equivalent resistance is defined to reveal the difference between the internal and external fault, not subject to the impact of the inrush current, non-periodic component, the transformer leakage impedance, intermittent angle. The new principle is very different with the differential protection. For the limitation of the existing time difference, the paper also proposes a new principle based on an improved time difference, which uses the wavelet transform to extract high- frequency details and singular point information. This paper introduces the spectral entropy into the transformer protection, using the physical meaning of entropy to reflect the inrush information in a cycle and constitute a criterion. This paper uses the two-instantaneous-value-product algorithm to extract the fundamental amplitude of current, and uses two factors (the time of reaching the maximum and the ratio of the first local maximum and the maximum) to constitute a criterion of the transformer protection. The new criterions of the transformer protection have been verified by a lot of dynamic experiments, which show the effectiveness of the methods.更多还原