【作者】 李荣明；

【导师】 王官洁；

【作者基本信息】 重庆大学 ， 电气工程， 2004， 硕士

【摘要】 小电流接地方式由于在保证运行维护人员的安全、过电压水平、设备绝缘水平、经济性等方面存在诸多的优点,所以一直被应用于我国的中低压电网中。但是对小电流接地选线的研究,到现在已经持续了50 多年,出现了较多的理论方法,也推出了很多的接地选线装置,但是,到目前为止,仍然没有令人十分满意的、选线准确率很高的保护装置出现,因而出现的接地选线装置的实际使用情况并不普及。究其原因,就在于现有的保护装置自身依赖的原理存在一定的局限性,而实际现场条件各不相同,这些原理所依赖的条件无法较好地满足,等等,限制了基于这些原理的保护装置的实际采用。而在生产实际中,中低压线路的故障,有70%以上都是单相接地故障,所以,寻找一种选线准确率高的保护装置,仍然具有相当重要的理论和实用价值。在此我们提出了零序基波暂态分量的选线方法,并配合零序有功分量的方向判别的辅助方法,构成了一套完整的接地选线保护。由于这种保护对动作时限要求不高的特殊性,我们研究了以已有的单相接地保护为基础,利用神经网络综合判别选线的综合方法,它可以弥补以前那些单一算法或原理构成的单相接地保护选线准确率低的缺点,更加能够适应现场条件的变化,而且能够从实际中来检验各种算法的优劣,总结出它们各自适合的现场条件,构成一个可以升级更新、智能化的系统。 采用的硬件平台主要由DSP器件TMS LF2407和CPLD器件EPM7128构成,采用的算法主要有方差逼近信号抽取法、神经网络的BP算法、提取各种频谱信号的FFT算法。 当然,这个课题的完成和产品化是一项比较复杂的、工作量很大的工作,但是相信它会给这一保护课题带来新的进展。更多还原

【Abstract】 Due to its superiority in the safeguarding of maintenance staff’s safety, over-voltage level, insulation of equipment and economy, the approach of non-solid grounded electric network has been widely applied in our country’s low & medium voltage level electric grids. Relevant studies have been conducted for the past 50 years and have produced a number of theoretical results as well as devices. Yet up to now no satisfying protection device with a high accuracy of fault-line selection have been achieved. As a result the actual application of those devices has not been popularized. The reason lies in the fact that the theories upon which these devices are established have their limitation, which is that the actual conditions cannot meet the desired requirements for the employment level of these devices. Nowadays 70% of failures with medium & low voltage level grids reside with single-phase grounding. Therefore to develop a protection device with a high accuracy rate of fault-line selection has important theoretical and practical value. Here we propose a fault-line selection approach of zero-sequence transient component of the fault current, which constitutes a complete protection for non-solid grounded electric network along with an assistant method of detecting the direction of the active component of the zero sequence current. Because of the extensive limit to response time, we have developed a comprehensive method by taking use of neural network based on our achievement of default-line selection. This method will make up for the shortcoming of low accuracy rate of single-phase-grounding line selection founded on single arithmetic or principles, which will be better accommodated to the changes of field conditions, compare various arithmetic, identify suitable field conditions and thus generate an easily upgradable and more intelligent system.The accomplishment and marketability of this subject is reasonably complex. Yet we are convinced that it will give momentum to the future developments in this research field.更多还原