【作者】 刘春；

【导师】 李红斌；

【作者基本信息】 华中科技大学 ， 电工理论与新技术， 2006， 硕士

【摘要】 随着电力系统数字化、网络化的发展趋势,传统的电磁感应式电流互感器因其固有的缺陷已越来越难以满足需要,正在逐渐被新型的电子式电流互感器代替。由于电力系统对设备的可靠性要求很高,新设备的采纳运用需要有一段较长时间的现场挂网运行考验时间。电子式互感器与一般传统互感器的二次输出接口不同,需要研究一套电子式电流互感器在线监测系统,对新型互感器运行期间的计量、保护通道的误差进行监测记录,以利于新设备的现场考核。LabVIEW是虚拟仪器(VI)的开发工具之一,它提供了丰富的数据采集、分析及存储的库函数,如FFT、数字滤波器等,还有形象而生动的工业级控件可供工业软件的界面开发,与常用的文本编程语言相比,有着独到的优势,非常适合用来做数字信号处理。本文设计了在LabVIEW平台下完成的电子式电流互感器在线监测系统。该系统对互感器的二次侧输出的模拟信号进行处理,计算互感器运行期间计量、参考通道的电流有效值、比值和相位误差等参数,将结果显示在工控机屏幕上,并具有数据库记录和查询、串口发送数据、简单过流故障录波等功能。本系统可用于各种不同测量原理的0.2级电子式互感器的在线监测。介绍了该系统数字信号处理部分的前端处理电路。提出了一种双通道放大的前端处理方法,并针对系统采用的PCI2008A型采集卡的具体情况,给出了具体的硬件和软件解决方案,实验结果显示采用该方案后,系统精度提高了一个等级。这种多通道放大的前端处理思想也可以用于电力系统其它场合,提高系统的整体精度。论述了该系统数字信号处理软件设计。研究了计量与参考通道的电流有效值以及二者的比差和相差的四种常用算法,从中选择了FFT算法并用LabVIEW语言实现。利用LabVIEW的ActiveX子模块搭建了系统数据库,实现了mdb数据库的动态创建、查询等功能。试验结果表明,该系统的精度均达到了预期的设计目标,能够用来在线监测0.2级电子式电流互感器的运行工况。更多还原

【Abstract】 For its inherent disadvantage, traditional electromagnetic current transformer is being substituted by new electronic transformer (ECT) gradually. The ECT has to be test for a long time before being adopted in grid. In order to observe the operating status of ECT, an on-line monitoring system is urgently demanded to calculate and record both the amplitude error and phase error between measurement channels and reference channels.Comparing to conventional text-style programming language, LabVIEW is more suitable for digital signal process in industrial filed, with its professional controls for industrial software interface design and abundant functions for acquiring, analyzing and storing data, such as FFT function, digital filter functions etc.In this paper, an on-line monitoring system based on LabVIEW platform was built for ECT. Second-side output voltage signals of ECT were processed. RMS, amplitude error and phase error between measurement channel and reference channel were calculated and displayed on the screen. Database, serial communication and simple record of over-current functions were also included. The system was available for all kinds of ECT with 0.2 grade accuracy.The front-end processing circuit for digital signal processing of the system was described. A scheme of double-channel amplification was brought up, and both hardware and software solutions according to the specific condition of PCI2008A DAQ board adopted in the system were provided. The experimental result indicated that adopting this scheme, the system has been raised an accuracy grade. The front-end processing idea of multi-channel amplification was also valuable to other applications of power system for improving the system accuracy.Digital signal processing software design for this system was described. Four conventional algorithms for current RMS, amplitude error and phase error were discussed, and FFT algorithm was selected from them and realized in LabVIEW language. System database was established with ActiveX module in LabVIEW platform where mdb database can be dynamically established and queried.The experimental result indicated that the system accuracy reached the anticipated design object, and the system was available for on-line monitoring operating status for 0.2 Class ECT.更多还原