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1、基于变压器中性点电流的在线监测系统的研究完泾平 王颖 刘连光华北电力大学计算机科学与技术学院，北京，102206摘 要：我国电网中已发现多次较大幅度地磁感应电流（GIC）侵扰事件，随着电网规模的增大，存在产生更大GIC的可能性。针对变压器中性点电流在线监测系统，运用计算机技术、通信技术和网络技术，实现对各检测点的中性点数据的远程采集、监测、处理。为深入研究我国电网受磁暴影响的可能性及其相关因素提供科学依据。关键词：磁暴；地磁感应电流；直流偏磁；监测系统；后台软件Study of Online Monitor System for the Geomagnetic Induced Current
2、on Power GridWAN Jing-ping, WANG Ying, LIU Lian-guangSchool of Computer Science and technology, North China Electric Power University, Beijing, 102206, ChinaAbstract Geomagnetically induced currents (GIC) in large magnitude have been found several times in Chinese power grids. With the development o
3、f Chinese power grid, larger GIC may be present in the power grids. Address monitoring system for power grid (GIC) system, use of computer technology, communications and network technology, to achieve the various points of the GIC detection of remote data collection, monitoring, treatment. For in-de
4、pth study of Chinas power grid by the effects of magnetic storms and related factors likely to provide a scientific basis.Keywords Magnetic storm, GIC, monitor system , DC magnetic bias, software exploitation1 引言太阳活动引起的地磁场剧烈变化称磁暴。磁暴感应的地面电场在输电线路、中性点接地变压器和大地回路产生地磁感应电流（Geomagnetically Induced Currents，
5、简称GIC）。GIC的频率约为0.010.0001Hz，这种准直流电流在变压器磁路产生偏置磁通，使变压器铁芯发生半波饱和。一方面对变压器造成不利影响12，另一方面励磁电流剧增使波形严重畸变，产生大量谐波对电力系统其它设备及整个电网安全运行造成危害3。这给电力系统安全稳定运行带来一系列的影响，这些问题已引起人们的高度重视。本文研制的变压器中性点电流在线监测系统，可对变电站变压器中性点和三相系统的电流等数据进行实时采集与处理，从而对了解、掌握电网GIC的水平、特点和规律，保证电网的安全运行，提供科学依据。2监测原理 变压器中性点电流与工频电流及谐波混为一体，并包含白噪声等干扰信号，会给测量带来很大
6、误差。因此，数据采集上来之后，需要对数据进行分析处理，处理方法包括数字低通滤波、快速傅立叶变换、二次取样、插值带通滤波等。对某个检测点信号单元进行检测信号处理的原理图见图1。图1 检测信号处理原理图 在采集线路电压、电流或变压器中性点电流时，必须考虑到防止高频信号的干扰，应该使用模拟或数字低通滤波信号处理方法。数字低通滤波算法设计中可采用优先格式法安排计算优先顺序，以实现直接标准型低通滤波对延时数据的存放。因此，监测装置优先选择数字低通滤波信号处理方法。 在对变压器中性点电流采样后，考虑到对于时间等方面的要求，以及中性点电流本身的特性，从而可以采用快速傅立叶变换信号处理方法。在数据采集和傅立叶
7、变换处理之后，要考虑到各次谐波的量值大小，并根据电能质量的相关要求确定要求记录的数据，即如果超过阙值就记录，否则就不记录。这样可以减少数据的不必要存储，节省存储空间。傅立叶在分析电力系统平稳信号中有着非常重要的地位，但是对于所测得的长时间变压器中性点电流数据，在数据变化较大，以及进行长时间的信号特征分析时必须进行二次采样，可去除交直流系统所带来的直流泄漏等方面的影响。3系统设计变压器中性点电流在线监测系统，针对各监测点的中性点电流数据进行远程监测、采集、处理和数据分析(如Dst指数分析、地域因素分析、干扰因素分析、影响因子分析等)，结合各地磁台的历史数据进行GIC的大小分析，以进一步研究我国电
8、网受磁暴影响的相关因素。3.1 系统体系结构系统主要由监控终端前置机、GPRS DTU、传输网络（GPRS网络和因特网）、监控中心组成。其结构如图2所示：前置机前置机前置机GPRSINTERNET图2监测系统体系结构图3.2 监控终端前置机的设置监控终端前置机是安装在变压器中性点接地端的监测装置。在变压器中性点接地处安装了霍尔传感器，利用霍尔电压传感器和电压/电流变送器的方式来测量输电线路或变压器中性线中的电流，通过FFT分析计算得到线路或变压器中性点中的GIC分量，同时对其进行采集、分析与数据存储。3.3 GPRS DTUGPRS DTU全称为GPRS数据传输单元，是专门用于将串口数据通过G
9、PRS 网络进行传送的无线设备。其内部封装TCP/IP协议栈，具有GPRS自动拨号和TCP/IP数据通信的功能。3.4 传输网络传输网络是指承担数据传输任务的GPRS网络和因特网，两者通过Gi接口相接，能够提供基于IP协议的透明数据传输。前置机采集的数据通过GPRS网络空中接口对数据进行解码处理，转换成在公网数据传输的格式，通过中国移动的GPRS无线数据网络进行传输，最终到达监控中心服务器的IP地址。3.5 监控中心监控中心是整个监测系统的核心，主要负责与各终端前置机的数据通信。监控中心服务器分配有公网静态IP地址，通过防火墙直接连接到因特网上。其上运行有监控后台软件，通过ADO.NET14与
10、数据库服务器连接，为用户提供系统功能，通过Web Service提供与其他MIS系统的数据接口。4 系统实现系统由若干功能模块组成，主要包括：GPRS通信、在线监测、数据处理、拓扑分析、报表处理、Web数据发布、日志管理、电子值班、绘图等模块以及辅助模块。各个功能模块相互协同完成监测系统的整体功能。4.1 数据通信由GPRS通信模块完成，用于完成前置机和监控中心后台软件系统的数据通信。4.2 实时监测由在线监测模块完成。通过实时监测界面对某变电站的变压器中性点直流电流值进行监视，具有实时动态曲线监视和曲线对比等功能。系统还提供的主要监测界面包括：变电站监测点地理分布图，每个安装有监测前置机的变
11、电站均在图中显示，每个监测点设有阀值，超过阀值时在图中显示为闪烁；遥测一览表，所有监测点的遥测值同时在一张表内显示；在不同的监测界面，通过丰富的右键功能，可以完成对相关历史数据的查询功能，可以以日期、时间、地点以及电流值为组合条件进行历史数据查询，支持图形与表格作为输出结果。4.3 报表处理由报表模块完成。报表模块支持用户自定义参数生成报表参数并将这些参数保存在系统描述数据库中，再通过访问系统历史数据库生成报表数据。报表类型分日、月、季、年等几种。报表参数和报表数据都保存在监控中心服务器上，支持Web Service发布及打印。5 运行实例系统采用浏览器/客户端（B/S）和客户端/服务器（C/
12、S）结合方式15组建，监控中心服务器对终端前置机的管理和数据通信采用C/S模式，充分利用客户端硬件资源，保证数据传输的实时性；后台软件采用B/S模式，给用户提供良好的可操作性和界面。中性点电流数据和预警信息发布通过Web Services来接口，实现了平台无关性，方便与电力系统的其他信息系统交换数据。如图3为前置机监控界面，图4为监控中心后台软件召测界面。图3 前置机监控界面图4后台软件召测界面5 结束语本文结合.NET技术，进行了变压器中性点电流在线监测系统的设计开发。系统在对电网GIC产生的机理、特征等分析基础上，结合国内地磁台的相关数据和我国电网的相关数据进行分析评测，可有效的监测磁暴发
13、生时变压器中性点电流水平，为分析地磁感应电流对电网的影响程度提供可靠的科学数据。参考文献1 Albertson V D, Thorson J M, Miske S A, et al. The effects of geomagnetic storms on electric power system J. IEEE Transactions on power Apparatus and System, 1974, PAS-93(4): 1031-10442 Albertson V D, Thorson J M, Clayton R E, et al. Solar induced current
14、s in power system: cause and effects J. IEEE Transactions on power Apparatus and System, 1973, PAS-92(2): 471-4773 Boteler D H., Pirjola R J, Nevanlinna H. The effects of geomagnetic disturbances on electrical systems at the Earths surface. Adv. Space Res., 1998, Vol.22: 17-274 Kappenman J G. Geomag
15、netic storms and their impact on power systems. IEEE Power Engineering Review, 1996, May: 5-85张清明.电网地磁感应电流监测预警系统研究：硕士学位论文.北京：华北电力大学（北京），20056张 浩电网地磁感应电流检测算法及装置研制硕士学位论文北京：华北电力大学（北京），20067孙 晨. 对GPRS在电力系统应用的分析J.电力系统通信. 2003，24(11):38-41.8赵丽萍.GPRS移动通信网络安全策略研究J微计算机信息.2004.89Jeffrey P McManus，Chris Kinsma
16、n美C#开发人员指南ASP.NET,XML Web服务与ADO.NETM北京：中国电力出版社，200210郝刚.NET经典范例Duwamish7大剖析JCSDN开发高手，2003，(3)：7-2511韩小涛，尹项根，张哲嵌入式Web服务器技术及其在电力系统中的应用J电网技术，2003，27(5)：58-6212Rebecca M.Riordan美ADO.NET程序设计M北京：清华大学出版社，200213Paul Dickinson美ADO.NET高级编程M北京：中国电力出版社，200214Ted Faison美Visual C#基于组件的开发M北京：清华大学出版社，2003完泾平，email：
17、wanjingping，通讯地址：北京德外朱辛庄华北电力大学442#出生年月：1981.3.3 民族：汉 籍贯：甘肃平凉 学历：研究生 Editors note: Judson Jones is a meteorologist, journalist and photographer. He has freelanced with CNN for four years, covering severe weather from tornadoes to typhoons. Follow him on Twitter: jnjonesjr (CNN) - I will always wonder
18、 what it was like to huddle around a shortwave radio and through the crackling static from space hear the faint beeps of the worlds first satellite - Sputnik. I also missed watching Neil Armstrong step foot on the moon and the first space shuttle take off for the stars. Those events were way before
19、my time.As a kid, I was fascinated with what goes on in the sky, and when NASA pulled the plug on the shuttle program I was heartbroken. Yet the privatized space race has renewed my childhood dreams to reach for the stars.As a meteorologist, Ive still seen many important weather and space events, bu
20、t right now, if you were sitting next to me, youd hear my foot tapping rapidly under my desk. Im anxious for the next one: a space capsule hanging from a crane in the New Mexico desert.Its like the set for a George Lucas movie floating to the edge of space.You and I will have the chance to watch a m
21、an take a leap into an unimaginable free fall from the edge of space - live.The (lack of) air up there Watch man jump from 96,000 feet Tuesday, I sat at work glued to the live stream of the Red Bull Stratos Mission. I watched the balloons positioned at different altitudes in the sky to test the wind
22、s, knowing that if they would just line up in a vertical straight line we would be go for launch.I feel this mission was created for me because I am also a journalist and a photographer, but above all I live for taking a leap of faith - the feeling of pushing the envelope into uncharted territory.Th
23、e guy who is going to do this, Felix Baumgartner, must have that same feeling, at a level I will never reach. However, it did not stop me from feeling his pain when a gust of swirling wind kicked up and twisted the partially filled balloon that would take him to the upper end of our atmosphere. As s
24、oon as the 40-acre balloon, with skin no thicker than a dry cleaning bag, scraped the ground I knew it was over.How claustrophobia almost grounded supersonic skydiverWith each twist, you could see the wrinkles of disappointment on the face of the current record holder and capcom (capsule communicati
25、ons), Col. Joe Kittinger. He hung his head low in mission control as he told Baumgartner the disappointing news: Mission aborted.The supersonic descent could happen as early as Sunday.The weather plays an important role in this mission. Starting at the ground, conditions have to be very calm - winds
26、 less than 2 mph, with no precipitation or humidity and limited cloud cover. The balloon, with capsule attached, will move through the lower level of the atmosphere (the troposphere) where our day-to-day weather lives. It will climb higher than the tip of Mount Everest (5.5 miles/8.85 kilometers), d
27、rifting even higher than the cruising altitude of commercial airliners (5.6 miles/9.17 kilometers) and into the stratosphere. As he crosses the boundary layer (called the tropopause), he can expect a lot of turbulence.The balloon will slowly drift to the edge of space at 120,000 feet (22.7 miles/36.
28、53 kilometers). Here, Fearless Felix will unclip. He will roll back the door.Then, I would assume, he will slowly step out onto something resembling an Olympic diving platform.Below, the Earth becomes the concrete bottom of a swimming pool that he wants to land on, but not too hard. Still, hell be t
29、raveling fast, so despite the distance, it will not be like diving into the deep end of a pool. It will be like he is diving into the shallow end.Skydiver preps for the big jumpWhen he jumps, he is expected to reach the speed of sound - 690 mph (1,110 kph) - in less than 40 seconds. Like hitting the
30、 top of the water, he will begin to slow as he approaches the more dense air closer to Earth. But this will not be enough to stop him completely.If he goes too fast or spins out of control, he has a stabilization parachute that can be deployed to slow him down. His team hopes its not needed. Instead
31、, he plans to deploy his 270-square-foot (25-square-meter) main chute at an altitude of around 5,000 feet (1,524 meters).In order to deploy this chute successfully, he will have to slow to 172 mph (277 kph). He will have a reserve parachute that will open automatically if he loses consciousness at m
32、ach speeds.Even if everything goes as planned, it wont. Baumgartner still will free fall at a speed that would cause you and me to pass out, and no parachute is guaranteed to work higher than 25,000 feet (7,620 meters).It might not be the moon, but Kittinger free fell from 102,800 feet in 1960 - at the dawn of an infamous space race that captured the hearts of many. Baumgartner will attempt to break that record, a feat that boggles the mind. This is one of those monumental moments I will always remember, because there is no way Id miss this.
