【作者】 郑涛；

【导师】 刘万顺； 刘建飞；

【作者基本信息】 华北电力大学（北京） ， 电力系统及其自动化， 2005， 博士

【摘要】 变压器是电力系统中重要的电气主设备之一,它在整个电力系统中起转换枢纽的作用,它的安全运行直接影响到整个电力系统的安全稳定运行。现代大型变压器容量大,电压等级高,造价昂贵,一旦因故障而遭到破坏,影响范围大,且检修时间长,检修难度大,在经济上必然遭受很大的损失。因此,研究和探索动作速度快,可靠性和灵敏性高的变压器保护新原理具有十分重要的意义。论文主要针对目前变压器主保护中尚未很好解决的一些难点问题进行了研究,提出了相应的解决措施。论文研究的主要内容和成果有: (1) 运用分形理论中的基本观点,阐明了铁磁材料的磁滞回环族是一种分形图形,从本质上揭示了铁磁材料动态磁化过程中所遵循的规律。创造性地提出一种“变压缩因子”的方法,通过对极限(主)磁滞回环进行线性迭代压缩计算来生成局部(次)磁滞回环,并仿真验证了这种方法的正确性。 (2) 创造性地提出一种采用数学形态梯度来提取电流波形特征,用于变压器励磁涌流和故障电流识别的新原理。设计了基于数学形态运算的峰谷检测器,用于提取电流波形的峰谷点。在计算电流波形峰谷点之间的数学形态梯度的基础上,提出了一种“三面积比较法”,用于识别变压器励磁涌流和故障电流。该原理能够定性区分变压器励磁涌流和故障电流,无需整定值,与变压器型号和参数无关;具有一定的抗 TA 饱和能力;不受衰减非周期分量的影响;计算量小。 (3) 深入分析了变压器 Y/Δ接线方式下等效瞬时电感的计算问题,针对Δ侧绕组环流对等效瞬时电感计算结果影响大,而又无法通过线电流计算得到的特点,提出一种变压器差动保护 TA 配置新方案。另外,从分析等效瞬时电感的变化入手,创造性地提出了一种基于归一化等效瞬时电感分布特性的识别励磁涌流和故障电流的方法。 (4) 首次提出一种基于数学形态梯度实现 TA 饱和检测的新原理。该原理设计思路新颖,与传统的“时差法”不同,仅需要检测故障发生时刻,不需要对差动电流出现时刻准确定位,能够实现在 TA 严重饱和情况下,对差动保护区内、外故障的准确识别。该方法计算简单,快速可靠,此外,该原理也适用于母差保护。 (5) 提出一种基于改进型序阻抗原理的变压器主保护方案,能够有效区分变压器区内和区外部故障,在一定程度上具有不受 TA 饱和以及 TA 变比不一致影响等优点。在前人工作的基础上,主要改进了象平面区域的划分,补充了励磁涌流识别判据,探讨了在特殊情况下应该采取的措施。更多还原

【Abstract】 Transformer is one of major electric apparatuses in power system. It plays an important role in the transmission of power supply. If it had a fault, the security and stability of power system would be greatly affected. Modern EHV transformers with large capacities have evolved to meet the increasing need of power system. On the other hand, if EHV transformers were damaged by faults, it would need a long time and great effort to repair them, for which, great economic benefits would be lost. Considering the serious consequence caused by faults in transformer, the research for new algorithm of transformer protection with high performance, such as fast, reliable and sensible capabilities, is in highly demand. The dissertation makes an investigation on some key problems, which are not well solved and still exist in transformer protection. Based on deep analysis and research, new algorithms to solve these problems are provided. The major contributions of this dissertation are as follows: 1)The dissertation proves that ferromagnetic element’s hysteresis loops is a kind of the fractal figure using the basic conception and definition of the fractal theory. Rules obeyed in the dynamic magnetizing procedure of ferromagnetic element are raised. A new algorithm based on the fractal theory that uses the “variable compressing factor” on simulating minor magnetic loops is put forward. Minor magnetic loops are emerged by using a linear-varied factor in compressing the major magnetic loop. Simulation results validate this idea. 2)A new algorithm of distinguishing the inrush and fault current of power transformer based on the character of current waveform extracted by morphological gradient is creatively put forward. Morphological detector, which is used to locate the peak and the bottom of current waveform, is designed. By calculating the morphological gradient between the peak and the bottom point of waveform, “three-area-compare” algorithm is originally put forward, which can be used to make the qualitative discrimination between the inrush and fault current. Protective setting values and parameters of transformer are no more needed. The proposed algorithm is able to distinguish the inrush and fault current with good performances, such as immune to CT’s saturation, little affected by decaying DC component and few calculations .etc. 3)The dissertation makes a deep analysis on the calculation of the equivalent instantaneous inductance of wye-connected transformer. It concludes that the looping current in the winding of delta side of transformer, which is hard to obtain from line current, severely influences the calculation result of equivalent instantaneous inductance. In that case, a new scheme of transformer differential protection is proposed. Considering the variation of the equivalent instantaneous inductance, an new algorithm based on the normalized equivalent instantaneous inductance for the discrimination between inrush and fault current is creatively proposed. 4)To prevent the mal-operation of differential protection because of current transformer(CT) saturation at out-zone fault, an algorithm based on the mathematical morphology is first put forward in this paper. Unlike the traditional time-differential method, this algorithm only needs detecting the time of fault occurred, while the time of differential current increased is no more needed. In the case of CT’s serious saturation, a discrimination between out-zone fault and inner-zone fault can be clearly made by this algorithm, which needs a few calculations and a short data window. In addition, the proposed algorithm can also be applied to bus protection. 5)A new transformer protective scheme based on the improved sequence-impedance algorithm is put forward in this dissertation. This algorithm has good performance in distinguishing transformer’s internal and external faults, and is immune to CT’s saturation and ratio-mismatch at certain extend. Based on the achievements of formers, this dissertation contributes in the following aspects, such as improving更多还原