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220kV地区变电所电气一次系统设计01,220,kV,地区,变电所,电气,一次,系统,设计,01
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2PB02 Active Shielding Design for a MVLV Distribution Transformer Substation Concettina Buccella Mauro Feliziani A lberlo Prudenzi Dept. of Electrical Engineering, University of LAquila, Poggio di Roio, 67040 CAquila, Italy prudenziing.univaq.it Tel.: +39-0862434437, Fax: 39-0862-434403, Email: , felizianing.univaq.it, Abstract The shielding of the low frequency magnetic field is obtained by using a system of fed active coils that produce a magnetic field opposite to the incident one reducing the total magnetic field. In this paper the design of a real active shield system is proposed to mitigate the magnetic field in the MVLV distribution transformer substation located at the Engineering Building of the University of LAquila. The design of the active shield system is developed starting from the experimental data obtained by the measurement of the magnetic field inside the MVLV substation. INTRODUCTION The recent exposure limits of human body to electric and magnetic fields at low frequency demands for a reduction of the extremely low frequency (ELF) fields I-9. The general public basbecome increasingly aware of possible effects fiom exposure to ELF magnetic fields. Recently, in a WHOOARC study the ELF magnetic fields have been classified as Group 2B “Possible Carcinogenic” on the basis on epidemiologic studies of childhood leukemia I. The traditional passive shielding technique is not always convenient to mitigate the ELF magnetic fields in some practical applications since a large quantity of material can be often required to build a shield adequate to mitigate low frequency magnetic fields. A better solution is to design a system of low frequency current coils, i.e. active shield, which produce a magnetic field opposite to the disturbing one in order to reduce the total magnetic field 6-7. By this way it is possible to obtain good shielding performances, often at a lower cost in comparison to the passive shielding technique 8-9. In this paper the development of an active shielding configuration is presented for the medium voltage (MV) / low voltage (LV) distribution transformer substation located at the Engineering Building of the University of CAquila. A scheme of the substation is shown in Fig. 2 where the MV and LV panels and the transformer cubicles are represented. Y Fig. 1 Sketch of the MVLV distribution transformer substation located inside the Engineering Building of the University of LAquila. ttttt MEDIUM VOLTAGELOW VOLTAGE DISTRIBUTION TRANSFORMER SUBSTATION The configuration of the examined MVLV substation with the layout of the power cables and bars is represented in Fig. 1. In the substation it is possible to identify the medium voltage bars at 20 kV, the transformer 20 kVl0.4 kV and the low voltage 0.4 kV bus bars of a switch board panel allocating four LV rising mains. Fig. 2 Map of the MVLV substation with the measuring points (+) inside the substation. The magnetic field has been measured by using the Wandel & Goltermann EFA 3 field analyzer system at the points (represented by the symbol + in Fig. 2) in the x-y plane at two altitudes: 1 . 2 m and .-1.7 m, according to the Italian technical standard 6. The distance between 0-7803-7277-8/0U$10.00 02002 IEEE. 350 two adjacent measuring points has been fixed as 25 cm along x- and y-axis. The spatial distributions of the magnetic flux density, B, measured in the x-y plane at z=1.2 m and F 1.7 m, are shown in Figs. 3 and 4 for a LV load of 9M) A. These measured values have shown that there is not a predominant component of the magnetic field inside the substation, hut all the field components along the x-, y-, and z-axes are present. Their percentage depends on the point where the field is measured. In order to design a suitable active coil system each component of the magnetic flux density (B, By BJ must be examined and shielded separately by independent active coils. x 0 1 Fig.3 Map of the measured r.m.s. magnetic flux density B in pT in the x-y plane at z=l.2 m. NUMERICAL MOD& The magnetic flux density inside the MViLV distribution transformer substation depends on the currents flowing into the conductors. A direct current I produces in the surrounding space a magnetic flux density B as: where Ar = r-r is the difference between the position vector r of the observation point P and the position vector r of the element dl , Equation (I) is assumed to be valid also to calculate low frequency magnetic fields in a homogeneous region. To this aim the conductor bars and cables have been discretized in wire sections where the known currents flow. By a simple numerical procedure, the magnetic flux density vector B has been calculated by superposition. Fig. 5 shows the computed and measured distributions of the magnetic flux density along the x axis at 0 . 2 5 m and 1 . 2 m. Considering the difficulty to identify the exact position of the sources and consequently the approximated values assumed for the distances between conductors, a good agreement between measured and computed values can be observed. (19 a8 - P (17 (16 - (15 (14 - (13 - A a5 1 1.5 2 25 3 35 4 Xlnl Fig.4 Map of the measured r.m.s. magnetic flux density B in pT in the x-y plane at z=1 .I m. ACTm SHIELD DESIGN By examining the measured map it is possible to design an active coil system which produces a magnetic field B, opposite to the incident B. In this way the total field Bt= B + B. can be reduced. From (I) it is possible to derive the magnetic field produced by a square loop current I. Assuming the square loop of dimensions 2 x 2 6 and parallel to the x-y plane at a distance d, the components of the magnetic flux density produced by the active shielding, B, B, and B, are given at the generic point P(x,y,z) by: where xi , yi are respectively the projections along the x- axis and y-axis of the distance between the generic point P(x,y,z) and the i-th comer of the coil, and 5 = dxi2 + yi 2 + (z - d)? is the distance between the i-th comer of the coil and the point P, as shown in Fig. 6. For several active coils the components of the magnetic field can be obtained applying the superposition. 35 1 kY 4.75 rn 0 0.5 I 1.5 2 2.5 3 3.5 4 4.5 0 X Fig.5 Measured (a) and computed (b) r.m.s. magnetic flux density along thex-axis at 1 . 2 m andr0.25 m. A system of 20 square coils, placed on the inner perimeter of the x-z plane at y=-1.5 m as shown in Fig. 7, absorbing a current equal to 2 A, has been built in order to attenuate the magnetic field in the proximity of the three cubicles inside the MVLV substation. Figs. 8 and 9 show the x- and y-components of the incident and total magnetic flux density at PO and 21.1.2 m for a LV load of 900 A. Figs. 10 and 11 show the same components in the same conditions, but at 1 . 7 m. In these figures the lines identified by the symbol a represent the measured incident magnetic flux density component and the lines identified by the symbol b the total computed magnetic flux density component. The maximum attenuation is obtained in the zone where the incident field is maximum, but an amplification of the magnetic field in proximity of the active coils is produced. t 1 2a dC I(d,-b,-a) Cd(d,b,-a) I 2b - Fig.6 Square loop in they-z plane. Fig.7 Active shield configuration. Fig. 12 (line a) shows the measured x-component of the incident magnetic flux density along the y-axis at 4 . 7 5 m and 1 . 2 m. A system of 100 square coils, placed on the x-z substation wall, at y=-1.5 m, feeded by a current of 15 A, has been used to shield the magnetic field density on the lateral z-y wall at 4 . 7 5 m. The magnetic flux density, in presence of this active shield system, has been measured and computed by the presented numerical procedure. The line identified by the symbols b shows the measured Bn and the line identified by the symbol c the computed total magnetic flux density at the same points. s o a5 1 1.5 z 25 3 35 4 X M 5 Fig.8 Measured incident field y-component By (a) and calculated total field y-component Bry with active shielding (b), a t 0 . 2 5 m and 1 . 2 m. 352 1 0 os 1 1 5 2 2s P 3s I I S x lml Fig.9 Measured incident field z-component B, (a) and calculated total field z-component Bn with active shielding (b), at y=O m and 1 . 2 m. 10 I I 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 x It -51 , Fig.10 Measured incident fieldy-component By (a) and calculated total field y-component BTy with active shielding (b), at y=0 m and 1 . 7 m. 1 I 0 0 5 1 1 5 2 2 6 1 3 5 I 4 5 x Irn1 Fig.11 Measured incident field z-component B, (a) and calculated total field z-component Bn with active shielding (b), a t p 0 m and 1 . 7 m. Fig.12 Measured incident field x-component B, (a), measured total field x-component Bn (b) and calculated Bn (c) with active shielding, at A . 7 5 m and 1 . 2 m. CONCLUSION In this paper the active shielding technique has been used to reduce low frequency magnetic fields. The design of an active shield system for the MV/LV distribution transformer substation located at the Engineering Building of the University of LAquila has been proposed. A system of square coils bas been able to produce magnetic field components opposite to the incident ones. Since the incident field presents a spatial behaviour very indented, the reduction of the magnetic field intensity is difficult. In order to attenuate the magnetic field in the proximity of the three cubicles a system of square coils has been used. The obtained maximum reduction of the magnetic flux density is about 60%. REFERENCES A i st1998. C. fkzcecellq C. Caruso M. Feliziani. :Reduction of low frc uency magnetic fields by fieldsontrolled active shields, EMC 2081. St. Petersbug Russia June 19-21 2001. 7 M. RebHedAndez abd G. G. Ka$&Attenuation of low fre ucncy magnetic fields usn active shie mg, Electric Power .!$sIefn Research, 45. 57-83 1998. 8 R. B. Schultz $E. Plank and D.E. Brush Shieldin lheo and ractice iEEE Tram. Eleclromog. Conpol., vol. f0, no?, pp. 9 R. G. Olse n ow frequenc s ieldng ofeleclmma e ic fie1 Proc. o Iff In: S mp on Jigj Vohage Eng., Mo&a!, Can$;: Aug.2!L29,199$ Ps7-20i. y 1988. 353 220kV变电所电气一次系统设计文献综述一、课题的背景和意义随着经济的发展和人民生活水平的提高，对供电质量的要求日益提高。电力已成为人类历史发展的主要动力资源，要科学合理的驾驭电力必须从电力工程的设计原则和方法上理解和掌握其精髓，提高电力系统的安全可靠性和运行效率。从而达到降低生产成本、提高经济效益的目的。220kV变电站作为当今城市的主要变电节点和用户的主要接入点，其直接关系到电网运行的可靠性、经济性1。本次设计的目的在于系统的掌握，增强了理论联系实际的能力，提高工程意识，锻炼独立分析和解决电力工程设计问题的能力。二、课题的研究现状目前，我国电力工业的技术水平和管理水平正在逐步提高，现在已有许多变电站实现了集中控制和采用计算机监控。电力系统也实现了分级集中调度，所有电力企业都在努力增产节约，降低成本，确保安全运行。随着我国国民经济的发展，电力工业将逐步跨入世界先进水平的行列。电力工业的发展，单机容量的增大、总容量在百万千瓦以上变电站的建立促使变电站结构和设计不断地陈改进和发展2-4。随着近几年计算机技术的不断提高，国内变电站的不断发展，为了适应新时代对变电站技术的要求，变电站必须进行技术改革，向着更为精准、自动化的有调控能力的方向发展5。目前变电站的发展趋于数字化、智能化、自动化。数字化变电站是以变电站一、二次系统为数字化对象，由智能化的一次设备和网络化的二次设备分层构建，采用标准化的网络通信平台6-7（IEC6185），实现信息共享和互操作，满足安全、稳定、可靠、经济运行要求的现代化变电站8。数字化变电站具有“全站信息数字化、通信平台网络化、信息共享标准化、高级应用互动化”等四个重要特征9-10：一、二次设备的灵活控制，具备双向通信功能，通过信息网进行管理，实现全信息采集、传输、处理、输出数字化；采用基于IEC61850的标准化网络体系；通过统一标准、统一建模实现变电站内外的信息交互和信息共享；实现各种站内/外高级应用系统相关对象间的互动，满足智能电网运行、控制要求11。智能变电站是智能电网的重要组成部分。当前变电站智能化升级改造的主要内容包括：一次设备智能化和在线监测、统一信息平台构建、运行维护智能化、辅助系统智能化改造12。其中，智能化辅助系统已成为智能变电站的重要支撑部分。智能化辅助系统纵向负责与上级统一信息平台的信息交互，横向负责与变电站自动化系统（SCADA系统）的信息交互和互动，以满足智能变电站对辅助系统的新需求13。变电站自动化的核心是其通信技术，从上世纪90年代开始，变电站自动化过程中先后出现过几种通信方案。最初是采用RS485总线将设备联系在一起，以主从的方式进行通信，但是这种通信方式比较简单，仍然是一种串行的点对点通信，有着很多技术缺陷。我国过去大量引入现场总线技术，并且由于总线技术有着简单易用以及组网方便的特点而在变电站自动化系统的建设当中广泛应用14。嵌入式网络单片机新技术在变电站自动化通信中得到了应用。常见的应用模式有两种：一是每个智能电子装置配置一个嵌入式以太网接口让每个智能电子装置作为一个以太网节点直接连到以太网上；二是几个智能电子装置通过RS485或者现场总线等方式连在一起，进而以曲入式以太网接口作为一个以太网节点连到以太网上。目前我国在那家的高压以及超高压变电站自动化系统通常都采用后一种模式，在完成通信功能的同时，还可以万有引力间隔控制单元完成本单元的测量以及控制等功能15。三、研究内容本次设计题目为设计220kV降压变电所一次系统，包括电气主接线的选择与比较，选择主变压器的容量和型号，计算短路电流，根据短路计算结果选择电气设备，最后进行防雷系统设计。（1） 主接线的设计变电站常用的主接线形式有：桥形接线，单母线接线，单母分段接线，双母线接线，双母线分段接线，带旁路母线制接线，3/2断路器接线。桥形接线分为内桥和外桥。内桥接线主要用于线路较长，不需经常切换变压器的情况；外桥接线主要用在变压器投入和切除操作比较频繁、通过桥断路器有穿越功率的情况下。单母线和单母分段接线形式接线简单、清晰，采用设备少、操作方便等特点。双母线、双母分段、双母分段带旁路接线形式主要用于配电装置的进、出线回路数多时，为增加可靠性和运行上的灵活性，可在双母线中的一条或两条母线上加分段断路器，形成两母线单分段接线或双母线双分段接线。一般用于110kV、220kV侧。双母线单分段或双分段接线克服了双母线接线存在全停可能性的缺点，缩小了故障停电范围，提高了接线的可靠性。3/2断路器接线形式有两条主母线，在两主母线之间串接三台断路器，组成一个完整串。每年串中两台断路器之间引出一回线路或一组变压器每一元件占有3/2台断路器。500kV侧多采用此接线16。（2）主变的选择主变压器的容量、台数，直接影响主接线和配电装置的结构。它的选择除依据基础资料外，还取决于输送功率的大小，与系统联系的紧密程度，同时兼顾发电机电压负荷增长速度等方面。（3）短路电流计算计算短路电流的目的主要是为了选择断路器等电气设备或对这些设备提出技术要求；评价并确定网络方案，研究限制短路电流的措施；为继电保护与调试提供依据。（4）电气设备的选择电气设备的选择在保证安全、可靠的前提下，并注意节约投资。电气设备要能可靠工作必须要按照正常工作条件进行选择，并按短路状态来校验热稳定和动稳定。（5）防雷接地设计根据防雷设计的整体性、结构性、层次性、目的性，根据周围环境、地理位置、土质条件以及设备性能和用途，采取相应雷电防护措施。对处在不同区域的设备系统进行等电位连接和安装电源防雷装置及浪涌电压保护装置，使得处在不同层次的设备系统达到统一的防雷效果。四、总结变电站是电力系统的一个重要组成部分，由电器设备及配电网络按一定的接线方式构成，它从电力系统取得电能，通过其变换、输送、分配，然后将电能安全、可靠、经济的输送到每一个用电设备的转换场所。作为电能传输与控制的枢纽，变电站必须改变传统的设计和控制模式，才能适应现代电力系统，现代工业生产和社会生活的发展。参考文献1 曹绳敏.电力系统课程设计及毕业设计参考资料M.水利水电出版社，1995.2 范锡普.发电厂电气部分第二版M.北京中国电力出版社，1995.3 西北电力设计院.发电厂变电所电气接线和布置M.水利电力出版社1992.7.4 西安交通大学.发电厂变电所电气主接线设计M，2000.5.5 王锡凡.电力工程基础M.西安交通大学出版，2000.1.6 熊信银.发电厂电气部分M.北京：中国电力出版社，2004.7 刘笙.电气工程基础M.科学出版社，2002.8 王士政.电力工程类专题课程设计与毕业设计指导教程M.中国水利水电出版社，2007.9 黄益庄.变电站综合自动化技术M.中国电力出版社，2001.10 陈跃.电气工程专业毕业设计指南M.中国水利水电出版社，2003.11 弋东方.电气设计手册电气一次部分M.中国电力出版社，2002.12 刘吉来，黄瑞梅.高电压技术M.中国水利水电出版社，2004.13 何仰赞.电力系统分析M.华中科技大学出版社，2002.14 周泽存，沈其工等.高电压技术M.中国电力出版社，2007.15 吴希再.电力工程M.华中科技大学出版社，2004.华北电力大学科技学院毕业设计(论文)任务书所在院系 电力工程系 专业班号 农电08k2 学生姓名 张洪源 指导教师签名 审批人签字 毕业设计(论文)题目 220kV地区变电所电气一次系统设计： 220/110/10kV，进/出线回数2/7/11 2012 年 2 月 19日一、毕业设计(论文)主要内容1. 查阅资料，熟悉课题，撰写开题报告。2. 变压器台数、容量确定及主接线设计。3. 短路计算。4. 电气设备选择及校验。5. 室内外配电装置设计。6. 防雷及接地系统设计。7. 翻译外文文献、撰写论文。二、基本要求1. 按照任务书的要求与进度完成毕业设计各个阶段的设计工作。积极主动与老师沟通，作好指导记录。2. 要求查阅具有权威性和代表性的文献资料，对论文研究领域的国内外动态形成较完整的认识。3. 变电站的设计应满足可靠性、经济性的要求。4. 设计方案合理、短路计算准确、设备选择适当、防雷设计切合实际。5设计成果： . (1) 设计说明书、计算书、设备概算表各一份。 .(2) 设计图纸基本要求
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