Analytical formula of induced electric fields in a spherical conductor by an ELF dipole magnetic field source

An analytical formula of induced electric field E in a spherical conductor by an ELF dipole magnetic field source is mathematically derived in vector form based on the equivalent mutlipole moment method with reexpansion technique (RE‐EMMM), where M _‖ and are parallel and perpendicular components of M , respectively. The validity of the formula is confirmed in the following three ways: (i) the derivation of the formula from the Sarvas equation with the reciprocity theorem derived by Eaton; (ii) the convergence of the formula to that of homogeneous magnetic field when M _‖ is located at the infinite distance; (iii) comparison of the analytical solutions with numerical solutions by RE‐EMMM. Furthermore, a formula for the trajectory, which satisfies E = 0 , is derived for the field by M _‖. © 2008 Wiley Periodicals, Inc. Electr Eng Jpn, 166(3): 8– 17, 2009; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20739     

Analysis of magnetically induced ELF current in biological spherical model with biomembrane

In this paper a biological three‐medium spherical model which consists of tissue, its membrane, and the extratissue medium is employed, and detailed distributions and characteristics of the induced current in the modeled structure are calculated by using a semianalytical solution developed for this model. It is demonstrated that both the change in the thickness and electrical properties of the biomembrane and the difference in conductivity between the inner and outer substances significantly affect the current passing through the membrane and the resultant profiles of the induced current. These analytical results are consistent with the experimental results, suggesting the influence of real membranes, and they indicate an important influence of the biomembrane on the induced current characteristics under specific membrane conditions. © 2001 Scripta Technica, Electr Eng Jpn, 135(2): 17–25, 2001     

Analysis of electric field induced by ELF magnetic field utilizing fast‐multipole surface‐charge simulation method for voxel data

This paper presents a fast‐multipole surface‐charge‐simulation method for calculating three‐dimensional Laplacian fields in voxel models. This method treats a surface of a voxel that has different inside and outside conductivities as a surface element of the indirect BEM (boundary element method). The main features of the proposed method are as follows. (1) An O(D²) performance in the memory capacity and operation cost is provided by applying the diagonal form fast multipole method (FMM), when the number of voxels is about D³. (2) The boundary matching is imposed by the continuity of the total flux passing through each element, which guarantees the solution globally satisfying Gauss's law; therefore the solution is globally stabilized. This method is successfully applied to calculate the electric field induced by an applied homogeneous ELF (extremely low frequency) magnetic field in a human head model that has 1 mm ×1 mm 1 mm voxel size. © 2008 Wiley Periodicals, Inc. Electr Eng Jpn, 165(4): 1–10, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20529     

Current distributions inside a cylindrical model of a human body with internal and external tissues having different conductivities in electric fields

The health effects of weak currents induced in a human body as a result of the interaction between the body and power line electric fields have been investigated. A body model (cylinder + hemisphere) filled with tissues having different conductivities was used to analyze internal current densities. In this analysis, only the magnitudes of the induced current densities were analyzed. In this paper, the finite element method is applied to the analysis of the distributions of the horizontal and vertical currents induced in the cylindrical model. The calculation method was verified by comparing the calculated results with experimental results obtained elsewhere. The basic characteristics of the induced current distributions in the cylindrical model with two tissues having different conductivities have been clarified. © 1998 Scripta Technica. Electr Eng Jpn, 122(3): 19–27, 1998     

A review of studies on the electric field and the current induced in a human body exposed to electromagnetic fields

How high an electric field or current is induced inside a human body when exposed to an electromagnetic field has recently attracted much attention. The background for this is twofold; concern about the possible health effects of electromagnetic fields (usually called ‘EMF issues’), and their positive application to medical treatment or new research subjects. This paper reviews various aspects related to this topic in terms of the following items: basic formulas for field calculation, effect of electromagnetic fields, calculation methods, an Investigation Committee in the IEEJ, and future research subjects. © 2006 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Analysis of Magnetic Field Distribution Under Power Lines with Changing Direction and Carrying Different Current

Transmission power lines are a common source of extremely low frequency （ELF） magnetic fields which are usually analyzed as serial lines in one direction. Overhead vertical-type double-circuit power li...     

放电电流密度对DMFC交流阻抗的影响

测试了膜电极组件(MEA)在不同工作电流密度(J)下的交流阻抗谱,并用等效电路L1R1 (CR2)[ QR3(L2R4)]进行拟合.内阻变化最平缓,先减小,后略微增大,变化幅度小于初始值的10％;阴极法拉第阻抗随着电流密度的增大而减小,当J＞ 1.00 A/cm2时,产生的水膜导致三相界面减少后,该阻抗又增大;阳极反应...     

高压交流输电线路曝露场强限值下人体感应电场和感应电流分析

人体处于高压交流输电线路下方时,会产生静电感应和电磁感应。当感应电压和感应电流数值过大时,会对人体造成伤害,为此国际非电离辐射防护委员会(ICNIRP)以及IEEE规定了人体在高压输电线路不同曝露情形下的曝露场强限值。首先运用有限元法,考虑人体对地绝缘和人体接地2种情况,分析了高压输电线路曝露场强典型限值下人体所产生的感应电压和感应场强的大小;接着利用解析法计算了不同曝露限值下的人体感应电流、感应电荷密度以及感应电流密度;最后将计算结果与ICNIRP导则给出的曝露限值进行了比较。结果表明,人体处于职业曝露限值场强10 kV/m下,人体内部最大感应场强为2.082×10-3 kV/m,感应电流密度为0.176 m A/m2,接近或低于ICNIRP导则规定的限值范围,不会对人体造成不适感。     

Analysis of control laws related to rapid electric drives of alternating current

The control laws of an ac rapid electric drive are analyzed. In these drives, the electromagnetic moment is formed if the energy of the magnetic field is stabilized. The control law that secures the most rapid formation of the electromagnetic moment under limited power is also examined.     

工频磁场作用下电能表锰铜分流器 感应电流的仿真分析

锰铜分流器作为单相智能电能表的电流采样装置,在工频外磁场干扰下会产生感应电流,进而影响电能表计量的准确性。文中先理论分析了锰铜分流器在工频磁场干扰下产生感应电流的物理原理,然后使用某公司的Flux软件对锰铜分流器进行有限元仿真分析,最后通过实验装置测量锰铜分流器在工频磁场中产生的感应电流,将仿真结果与实测结果作对比分析,验证了仿真结果的准确性。     

Measurements and predictions of electric and magnetic fields from power lines

Electric and magnetic field measurements around overhead and underground power lines have been performed extensively within a transmission and distribution electric grid. Measurements have been performed at different heights of the human body close to such transmission and distribution power lines that operate at a frequency of 50 Hz, at different currents and at three different voltages of 11, 66 and 132 kV. These measurements were performed in an attempt to firstly verify that the existing measurements fall within the signified guidelines for electric and magnetic field exposure, published in 1998 by the International Commission on Non-Ionizing Radiation Protection. Furthermore, and most importantly, were used to validate/develop a model capable of predicting the magnetic field produced in both overhead and underground transmission and distribution power lines using experimental measurements. This is achieved by establishing a linear correlation between the current load of one of the two three phase circuits and the magnetic field, in an attempt to predict the magnetic fields produced in power lines using the SCADA system at overloaded periods.     

Study on dependence of AC transport current losses in YBCO‐coated conductors on distribution of critical current density and n value

We measured AC transport current losses in three kinds of thin‐film YBCO‐coated conductors made by different processes. The results showed that the loss characteristics were different and that some of the conductors did not follow the Norris strip model which is generally believed to well explain the loss characteristics of YBCO conductors. In the paper, an analytical model in which distribution of critical current density and n value of the conductor are taken into consideration is proposed to describe the AC transport current loss characteristics more generally than the Norris strip and elliptical models. It is shown that the analytical model explains well the measured loss characteristics of the three kinds of conductors. © 2005 Wiley Periodicals, Inc. Electr Eng Jpn, 152(2): 26–38, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20056     

凸极冲击发电机端部结构及磁场分析

本采用准三维有限元端部涡流场计算方法,针对一台ＴＦ２００－８／２１５０型凸极冲击发电机的端部结构设计要求,经过理论分析、多种方案计算以及试验验证表明,推荐的部结构既具有电机端区磁场分布合理、结构件损耗小、温升低,在工程上又具有低成本,工艺上简单易行的特点。所提出的计算方法合理实用,精度完全满足工程计算的要求,可推广应用于定子采用整圆压板的常规凸极同步电机端部磁场计算。     

自耦变压器绕组漏磁场及涡流损耗的二维数值分析

利用ANSYS软件建立了油浸式自耦变压器的有限元模型,采用“场-路耦合”方法分析了变压器绕组的漏磁分布,得到绕组的涡流损耗分布情况.将有限元计算结果与工程计算结果对比,说明了计算方法的准确性,对自耦变压器的设计具有一定的理论参考价值.     

高海拔地区特高压杆塔的合成电场和电位转移电流实测研究

针对2000 m高海拔地区±800 kV特高压直流带电作业过程中,作业人员将承受特高压杆塔产生的合成电场和电位转移电流的问题,开展了特高压杆塔的合成电场和电位转移脉冲电流的实测研究。首先,从理论上分析了考虑离子流条件下特高压杆塔的合成电场计算方法和电位转移电流特性。然后,建立特高压杆塔带电作业和电位转移有限元仿真模型,并进行了仿真计算分析。最后,在高海拔特高压试验基地搭建了试验平台和测试系统,开展了特高压杆塔的合成电场和电位转移脉冲电流的现场实际测量工作,试验结果可以为高海拔地区特高压杆塔带电作业的安全防护标准提供制定依据。     

偏心及返回导体对特高压用计量CT误差影响分析

为明确电能计量装置自身误差受电磁场影响程度,对特高压用计量电流互感器(CT)开展一次绕组偏心及返回导体对误差影响的定量分析。首先根据磁路平衡原理建立在圆柱坐标内CT误差数学模型,推导出不同位置的外加磁场点对CT误差影响计算公式,并结合实例得到有限元与解析解结果一致,证明推导公式的正确性;然后在二维电场中对1 000 k V工程中典型CT尺寸及一次电流进行磁场分布仿真,定量的得到对于特高压用计量CT,一次绕组偏心大于1/8的CT半径后会铁心内部会产生局部饱和,导致误差产生突变进而导致超差可能;此外,仿真结果指出外部返回导体距离CT中心应大于3倍CT半径后,返回导体引起的磁场对CT误差的干扰才能被忽略;最后搭建实际特高压误差测试平台对一次绕组偏心开展试验,测试数据与仿真结果趋势一致。     

变电站220 kV及以上区域工频电磁场强度特性分析

针对500 kV变电站内500 kV配电区域的工频电场强度普遍高于220 kV配电区域和35 kV配电区域、变电站工频电场强度超标点主要集中于500 kV配电区域和220 kV配电区域等状况,选取6座不同类型的500 kV变电站进行500 kV配电区域和220 kV配电区域电磁场强度检测,分析并总结出500 kV变电站...     

500 kV变电站工频电场的测量与分析

为了掌握500 kV变电站的工频电场分布,采用EFA-300低频电磁场分析仪,选取50Hz带通滤波、最大有效值方式,在某500 kV变电站厂区内,每间隔6 m测量电场强度值,将1092个测量数据绘制成电场强度分布图,找出其中电场强度较高的区域。测量结果显示,除个别区域外变电站内工频电场基本满足ICNIRP标准限值,分析变电站电场分布规律表明,电场强度较高的区域集中在主变、开关、断路器、互感器等设备及其连接线附近的区域,且场强最大值位于三相中的边相附近,应重点考核这一区域的工频电场值。     

高压直流双回输电线路合成电场与离子流的计算

高压直流双回输电线路在我国尚无设计与运行经验。为此,文章对双回直流线路电晕效应产生的离子流与综合电场强度进行了计算,分析了导线不同的布置方式以及线路间距、对地高度、导线分裂数、导线半径等结构参数对地表离子流和场强的影响。结果表明,两回线路上下排布方式的地表合成场强与离子流密度较小;在相同导线尺寸与同等架设高度下,合理排布的双回线路的地表场强与离子流远小于单回线路,且双回线间距越小地表场强与离子流越小;同塔双回线路的电磁环境要优于单回线路。     

750 kV交流输电线下人体的工频电场效应分析

随着输电线路电压等级的不断提高,工频电磁场问题越来越受到人们的关注。分析了750 kV输电线路下简化人体模型的电场效应,构建了双手下垂、双手上举、撑伞以及行走的人体模型,比较了不同姿势下人体感应电场的分布情况。以双手下垂模型为例,研究了架空输电线离地高度对人体电场效应的影响。仿真计算结果表明,人体的存在会使其所在空间的电场分布发生畸变,人体姿势的改变会影响感应电场的分布情况,局部场强最大值总是出现在人体轮廓的尖端部位,导线离地高度越大,其下方人体的感应电场值越小。不同姿势下人体模型的局部场强最大值在允许的数值范围之内,750 kV超高压输电线路的工频电场不会对人体健康造成危害。