【作者】 邵敏茹；

【导师】 王保保；

【作者基本信息】 西安电子科技大学 ， 计算机应用技术， 2009， 硕士

【摘要】 电力变压器是组成电力系统的关键设备,其安全运行是保证供电可靠性的基础。局部放电是造成变压器设备绝缘劣化的主要原因之一,也是其绝缘劣化的重要征兆和表现形式。所以准确有效的监测变压器内部局部放电的放电量和放电位置是保证变压器正常运行的关键。本文在分析国内外局部放电定位技术发展现状的基础上,重点研究了局部放电超声信号去干扰与局部放电定位两个方面的问题,提出了相应的算法并设计开发了局部放电超声定位系统,具体内容如下：针对现场强烈的噪声干扰,提出一种新的方案：将多分辨经验模式分解应用于局部放电超声信号去干扰中。多分辨经验模式分解将小波变换的多分辨分析思想引入传统的经验模式分解,很好的克服了传统经验模式分解的模态混叠现象和计算量大的缺点。该算法能够有效地从包含噪声的现场信号中提取超声波信号,为局部放电定位奠定良好的基础,实验结果表明了算法的有效性。针对变压器局部放电定位问题,提出使用新的优化方法——梯度收缩法来计算局部放电点的坐标,并对该方法进行了严格的论证和实验。梯度收缩法是一种新型高效的计算机寻优算法,该算法能使目标函数梯度的模逐渐收缩到零,以达到目标函数极小化,其综合了牛顿法和共轭梯度法的优点。现场定位结果表明,梯度收缩法能够有效地求解局部放电定位问题,并优于传统的局部放电定位算法。根据上述算法,本文设计并开发了基于虚拟仪器的局部放电超声定位软件系统,本系统以图形化编程语言LabVIEW为核心,实现了读取局部放电超声信号、局部放电信号去干扰、局部放电定位、用户管理等功能,为变压器局部放电点的准确定位提供了一个有效的平台。更多还原

【Abstract】 Power transformer is one of the most important instruments in power system, by whose safety running the credibility of power supply directly will be influenced. Partial discharge is the main reason for insulation ageing of high-voltage electrical equipment, and also an important symptom and manifestation of insulation ageing. So, for keeping power transformer normal, it is crucial to monitor the discharge location and electric capacity effectively and precisely. Based on analyzing the development of discharge location technology, this paper pays attention to the study for the discharge resource location and de-noise for partial discharge signal, and proposes approach to solve the two problems and development of the software platform. The main contributions can be summarized as follows:Firstly, partial discharge signal de-noise methods are studied, and multi-resolution EMD is employed to remove the noise of the signal collected in the field. Introducing multi-resolution to traditional EMD, multi-resolution EMD successfully solves two problems of traditional EMD:modal mixture and computation quantity. This method can effectively extract partial discharge signal from the site signal and provide a basis for the discharge resource location. The result shows that the proposed approach is effective.To calculate discharge source, a new optimization algorithm, gradient shrink algorithm is applied and derived. Gradient shrink algorithm is a new optimization algorithm for unconstrained functions, and it is expected to cause the Euclidean norm of the gradient of objective function gradually shrinks to zero in order to minimize the object. Field result shows that gradient shrink algorithm can effectively locate discharge source and is greatly superior to traditional methods.Using the two methods above, this paper developes a soft system of ultrasonic locating based on virtual instrument. The system based on the graphical programming language LabVIEW can implement several functions such as filtering the on-line detection data, locating discharge source and so on, and provide an effective platform for the location of discharge source in power transformer.更多还原