500 kV变压器单相替换引起参数不一致的运行研究

本文结合500 kV某站#2主变大修,探讨用参数相近的相邻500 kV站备变对该500 kV站备用变进行单相替换的案例,从主变正常运行下的关键指标、故障条件下对保护的影响等方面考虑,采用仿真计算软件PSCAD对该500 kV站#2主变A相替换前后电压电流不平衡度、故障电流及过负荷电流进行仿真分析,探讨500 kV主变单相替换的可行性。

An Introduction Effect Evaluation Tool for Distributed Generators

This paper presents practical distribution system equipment models such as various distributed generators, voltage regulators, and loads for fast three phase unbalanced load flow calculation in distribution systems. The method can calculate voltage and current of distribution systems, in which distributed generators are introduced. The calculation time of the proposed method is about 40 times faster than that of the Newton-Raphson method. Moreover, an introduction effect evaluation tool for distributed generators using the proposed three phase unbalanced load flow calculation is presented. It provides various functions such as a power system network diagram creation function and a voltage profile chart display function. Therefore, the introduction effect evaluation of distributed generators in distribution systems can be evaluated quite easily.

基于相序分解与线电压有效值的三相不平衡度定义与原理探究

针对原有三相不平衡度定义的各种缺陷,提出一种基于相序分解、三相线电压的有效值表征的三相不平衡度ε_(unb)。通过理论推导,得到正序分量U_1和负序分量U_2,二者是关于三相线电压的函数关系。根据U_1和U_2的数值关系,首先分别计算三相平衡度ε_b=U_1~2/(U_1~2+U_2~2),再根据ε_(unb)=1-ε_b分别计算三相不平衡度。理论分析表明,三相不平衡度ε_(unb)恒处于区间[0,1],且当U_1>U_2时,正序分量占据主导地位,ε_(unb)<50%;当U_1<U_2时,负序分量占据主导地位,ε_(unb)>50%。改进后的三相不平衡度定义不仅更加贴近理论本质,而且无需测量相位,为理论分析和工程应用提供了便利。