【作者】 袁兆强；

【导师】 张承学；

【作者基本信息】 武汉大学 ， 电力系统及其自动化， 2013， 博士

【摘要】 随着我国坚强智能电网战略的不断推进,超(特)高压电网建设也加快了推进步伐。因此,电网的安全稳定运行对继电保护的动作速度提出了更高的要求。传统的输电线路纵联电流差动保护由于动作灵敏、能够可靠地保护线路的全长,不受系统振荡和运行方式变化的影响,因此得到了广泛应用。但是,由于它是基于工频故障信息的,动作速度较慢,且受电流互感器饱和及过渡电阻、线路分布电容等因素影响,难以适应超(特)高压、长距离输电技术发展的需要。因此,国内外学者提出了基于故障暂态电气量的超高速继电保护方案,其中行波差动保护是一个重要的研究领域。行波差动保护利用线路两侧方向电流行波的差值构成保护判据,动作速度极快,且不受过渡电阻、分布电容、系统振荡、电流互感器饱和、母线结构等因素的影响,具有很大的实用价值。本文在前人研究成果的基础上,围绕行波差动保护特征量的选取、利用、去噪、适用范围等问题开展研究工作。本文的主要研究内容和取得的成果包括如下几个方面。1、系统地研究了超(特)高压输电线路的波过程。首先研究了单相分布参数导线的波动方程及其在给定边界条件下的解析解,探明了行波在输电线路上的传播规律,以及在波阻抗不连续点(即母线处)行波的折反射规律。然后,将单相导线波过程演绎到三相输电线路的情况,引出了相模变换概念。在分析了常用相模变换(克拉克变换和凯伦贝尔变换)存在问题后,导出了一种新的相模变换方法及相模变换矩阵。利用该方法进行相模变换后,所获得的任意一种线模量(1模量或者2模量)都能够反映任何类型的故障。凯伦贝尔相模变换和克拉克相模变换中的任意一种线模量不能反映所有类型的故障,在构造保护算法时,不得不同时采用两种线模量(1模和2模),因此使得保护的计算量增大。采用本文导出的新型相模变换方法,只需要应用一种线模量来构造行波保护算法,因此减少了计算工作量,提高了保护的动作速度。本文还提出了选用较大的线模量构造保护算法的方法,即虽然本文导出的新相模变换方法可以只用一种线模量,但是应该选用较大的线模量以提高保护的灵敏性。具体方法是：当故障选相元件给出的是BG、BC、AB等三种故障类型时,应选用1模量；当选相元件给出的是AG、CG、CA等三种故障类型时,应选用2模量；而当故障选相元件给出的是BCG、ABG、CAG及ABC等四种故障类型时,应比较1模量和2模量,选用较大者。2、为了解决行波信号的去噪问题,本文系统地研究了形态学滤波器和形态梯度算法。本文从集合论的角度研究了形态学基本运算——腐蚀和膨胀的运算规律及其对结构元素的要求,强调为了行波保护准确地提取到行波波头到达母线的时间,结构元素的几何中心必须选择在原点。然后,分别研究了形态开-闭滤波器和形态闭-开滤波器、形态交替组合滤波器、多分辨率形态滤波器以及形态梯度算法,在此基础上,选择了一种结构元素长度线性增长的多分辨交替组合滤波器作为前置滤波器,并且利用交替组合滤波输出结果构成的抗噪形态梯度算法作为提取方向行波突变时刻的工具。3、在总结前人研究成果的基础上,提出了利用保护安装处的线模方向电流行波波头的积分值作为保护的特征量,以线路两端特征量的差值来构成行波差动保护的动作判据的方法。以500kV电网为例,通过对被保护线路内、外部发生经各种过渡电阻发生各种类型短路情况的大量仿真计算,验证了所提出的行波差动保护方案的正确性和有效性。4、由于超(特)高压输电线路为了解决工频过电压、运行电压过高、单相重合闸期间潜供电弧熄灭等问题,往往会在线路两端安装中性点带小电抗的三相并联电抗器。为了探究本文提出的行波差动保护方法是否适用于带并联电抗器的输电线路,研究了带并联电抗器的输电线路在内外部发生短路故障时,行波在跨越并联电抗器安装点前后的传播规律,从理论和仿真计算两方面证明了本方法适用于带并联电抗器的输电线路。更多还原

【Abstract】 With the development of the strategy of the diversion of natural electricity from the western to the eastern regions, the EHV/UHV grid is building rapidly. Consequently, the speed of action of the relay protections must be higher than beforetime to meet the demands for the safe and stable operation of the EHV/UHV grid. The conventional current differential protection of transmission line acts sensitivity, and can protect the total track length of transmission line reliably. And it doesn’t be affected by the oscillation of power system and operation scheme changes. Therefore,it is widely used.But the conventional current differential protection acts more slowly because it works based on power frequency signals, and it may be affected easily by the saturation of the current transformer,transition resistor,distribution capacitance,and so on. Therefore it difficults to adapted to need of development of the EHV/UHV grid and long distance power transmission. Some scholars at home and abroad put forward several schemes of ultra high-speed relay protection based on fault transients, the travelling wave differential protection is an important research field.The travelling wave differential protection makes up the action criterion with the differentials of the direction current travelling wave both ends of transmission line. Its action speed is very rapidly, and it doesn’t be affected by the transition resistance, distribution capacitance, oscillation of power system, saturation of the current transformer,busbar structure and so on. Therefore it is very useful. This dissertation systematically researches the choose of the characteristic quantity of the travelling wave differential protection,the uses of,the filtering,the applicative range of the protection. The main contents and contributions of this dissertation are as follows:1. The travelling wave process on the EHV/UHV transmission line is systematically and completely researched in this dissertation. First of all the analytic solutions of the wave equations of the single phase distribution parameter lead wire at given the boundary conditions are investigated, and the travelling wave spreading law on the transmission line and the refraction and the reflection law of it at the point of the wave impedance discontinuousness are discussed.Afterward, the travelling wave process of single phase lead wire is deducted into the three-phase transmission line, the concept of phase-mode transformation is led out. After analyzing the problems of the frequently-used phase-mode transformation (Clarke and Karenbauer), this dissertation deduces a novel phase-mode transformer and its new transformation matrix. By using this new phase-mode transformation we can obtain any one of the line mode quantity (1mode or2mode) which can reflect all types of fauls. Any one of the line mode quantity of the Clarke phase-mode transformation and Karenbauer phase-mode transformation can not reflect all types of fauls, two line mode quantities have to be used as constructing the algorithm of the relay protection, for this reason, the calculated amount of the algorithm is huge. By new phase-mode transformation, only one line mode quantity is used for constructing the algorithm of the relay protection. Therfore, the calculation workload is decrease, the action speed of the protection is increase.A menthod of selecting bigger one both of the1mode and2mode quantity in constructing the algorithm of the protection is proposed too in this dissertation, which can improve the sensitivity of the travelling wave differential protection. The pratical methods are:while the phase selector exports the BG,BC,AB,we must choose1mode quantity,while the phase selector exports the AG,CG,CA,we must choose2mode quantity.If phase selector exports the BCG,ABG,CAG or ABC,we mast choose bigger one both of the1mode and2mode quantity.2. In order to filter out the noise in the travelling wave, this dissertation systematically researches the morphological filters and the morphological gradient. In this dissertation, we research the corrosion operation and expand operation from the standpoint of the set theory. For the sake of accurately measuring the time of the head wave arrived the busbar, the geometry center must be at coordinate origin. After discussing respectively the morphological open-close filter and close-open filter, the morphological alternation combination filter, the multiresolution morphological filter, and the morphological gradient, this dissertation presents a new multiresolution morphological alternation combination filter whose structure element’s length is growing linearly and a new noise cancelling morphological gradient whose input signal is the export of the multiresolution morphological alternation combination filter.By simulation computation, a multiresolution morphological alternation combination filter applicable to the travelling wave differential protection and a noise cancelling morphological gradient are selected.3. On the basis of the research achievements of our predecessors, the novel method that selects the integral quantity of the direction current travelling wave in between head wave and very short time after as the characteristic quantity of the travelling wave differential protection is proposed in this dissertation. The new action criterion of the travelling wave differential protection is the differentials of the characteristic quantities both ends of the protected transmission line.Take some500kV power grid for illustration, by large numbers of simulation computation, the correctness and the effectiveness of the new travelling wave differential protection are verified.4. In order to verify the proposed travelling wave differential protection is true of the transmission line with the shunt reactor or not, the. travelling wave transmition law when it across the point of a shunt reactor set up is studied whateyer the fault takes place inside of the transmission line with the shunt reactor or outside.By theory and practice of simulation, we full prove the proposed method is true of the transmission line with the shunt reactor.更多还原