【作者】 黎功华；

【导师】 杨浩；

【作者基本信息】 重庆大学 ， 电气工程， 2008， 硕士

【摘要】 变压器是完成不同电压等级电能转换的枢纽,是电力系统最重要的电气主设备之一,其运行状态直接影响着电力系统的安全稳定运行。变压器也是造价十分昂贵的电气主设备,应根据需要设置相应的保护。近年来,变压器保护动作正确率一直较低,远远低于线路保护和发电机保护,且有原因不明的误动,现有的变压器保护已不能满足电力系统的需要。因此,研究更为有效、可靠的变压器保护原理,对提高变压器保护的性能具有非常重要的意义。论文首先介绍了现有的变压器差动原理以及存在的不足,对变压器主保护方案的一些新思路做了较全面的综述。论文对现有的基于变压器模型的保护原理存在的不足进行了分析,指出其根源在于忽略了含有三角形绕组时三相绕组不平衡对绕组回路的影响。从变压器基本回路方程出发,利用三角形侧绕组内的不平衡电流来联系三相回路方程,得到了表示正常运行的变压器绕组回路平衡方程模型,该模型考虑了三角形侧不平衡三相绕组中任意一相绕组对原、副边其他两相绕组的影响。根据变压器发生内部故障时,绕组参数发生变化,该等式不再成立这一特征,提出了基于绕组平衡方程的变压器保护原理,并给出了判据。实现基于绕组回路平衡方程的变压器保护原理的关键在于准确获取绕组回路平衡方程的系数。由于被估计的参数,可根据其物理特性及变压器铭牌数据,获得比较多的信息。因此,提出了利用约束最小二乘估计算法来对变压器绕组平衡方程的系数进行估计。针对变压器保护研究的需要,在分析和总结前人经验的基础上,建立变压器数字仿真和动模仿真模型,仿真了典型的变压器运行工况,并记录了电压、电流数据。利用仿真数据对提出的新原理进行了验证,取得了良好的效果。更多还原

【Abstract】 Transformer, as one of the most important and costly major apparatuses in the power system, is the hinge to transform electric energy in different voltage, whose running state will affect the safety and stability of the power system. It should be set corresponding protection. Recently, transformer protection is always in poor performance, which is far less than line protection and generator protection, and exist unknown reasons mal-operate. The existing transformer protections haven’t satisfied the demand of the power system. Therefore, research on more effective and more reliable transformer protection scheme is very important for improvement the performance of transformer protection.The paper firstly introduces the existing transformer differential protection and its shortage, and summarizes the new ideas of transformer main protection.The shortage of existing transformer protection principle based on the transformer model is analyzed, and which stems from ignoring the effect of three-phase unbalance winding in delta side to winding loop is be pointed out. Based on the loop equations of transformer, utilizing the unbalance current in the delta windings to contact the three phases loop equations, the winding loop equilibrium equation model represented the normal running transformer is obtained. The novel model takes into account the impact that a random phase of delta windings acts on the other two phases of primary and secondary windings. According to the characteristic that the equation is not valid while the winding parameters change due to the occurrence of internal fault, a novel transformer protection principle based on the winding loop equilibrium equation and its criteria are proposed.The key problem of realizing the novel transformer protection principle is how to obtain accurate parameters of winding loop equilibrium equation. On account of more parameters information getting from the physical characteristic and data plate of transformer, constrained least squares algorithm is put forward to estimate the parameters.For the demand of transformer protection research, on the basis of analyzing and summing up previous experience, digital simulation model and dynamic imitation model are established, and the representative running states of transformer are simulated, recording the voltage and current data. Adopting the simulated data to verify the proposed principle, good performance is shown from the calculated results.更多还原