确定工频磁场公众曝露限值的分析

工频磁场公众曝露限值的确定是我国工频电场、磁场曝露限值国家标准制定的关键因素。为此结合各国工频磁场限值采用情况以及电磁场人体健康影响的医学评估结果,分析了我国典型输电线路以及特殊线路情况下的工程磁感应强度状况。通过世界卫生组织(WHO)"国际电磁场计划"的调查统计可以看出,采用WHO推荐的国际标准已成为国际主流趋势,中国需要引起重视;目前国内输变电线路正常运行时周围环境中的磁场水平确实不高,但并不表明可将磁场限值降低到某个任意的水平,相反还需考虑到线路运行状况、采用新的导线技术和电缆运行等因素,这些均会使工频磁场水平显著增高。     

特高压工频电磁场对人体健康影响及其曝露限值

我国输变电工程在建设过程中遇到的环保纠纷日益增多,工频电场、磁场曝露限值问题一直没有国家标准可以依循是其重要原因之一。因此在我国交流特高压输变电工程建设的背景下,就目前在输变电工程建设过程中遇到的纠纷事件,结合我国特高压工程电磁环境状况,并考虑国际相关标准和导则采用情况以及世界卫生组织(WHO)"国际电磁场计划"的电磁场人体健康影响的风险评估结论,对国内一些不同观点进行探讨分析,针对工频电场和磁场的健康影响以及曝露限值的确定进行分析,说明工频电场和磁场对居民区没有重大环境影响;针对我国工频电场、磁场曝露限值制定以及ICNIRP导则的研究方法和技术问题,提出需要注意分析国内一些不同观点对ICNIRP导则的解读正确性。     

国际标准工频电磁场公众曝露限值比较及启示

为了促进我国电磁场控制限值国家标准的出台,针对输变电工程的工频电场和磁场,介绍了世界卫生组织推荐的国际非电离辐射防护委员会(ICNIRP)导则和电气与电子工程师学会(IEEE)标准在电磁场基本限值、参考水平以及最大允许曝露等方面的规定和变化,比较分析曝露限值的应用原则、制定依据及防护措施,由此提出对我国电磁场控制限值的具体建议,得到结论:IEEE标准较ICNIRP导则更多地考虑了具体工程环境下的限值处理问题;用参考水平或最大允许曝露来确定是否符合或者超过基本限值;建议国家标准同时采用4kV/m和10kV/m两个电场控制限值,保留100μT作为磁场控制限值.     

云数据中心与变电站共站时的工频磁场防护策略

云数据中心(IDC)与高压变电站共站建设时,变电站的工频磁场会对共站址建设云数据中心的信息存储设备产生不良影响。为了确定云数据中心合理的工频磁场限值、确保云数据中心信息设备的电磁安全,比较分析了云数据中心工频磁场的测量结果、计算结果及公众全天工频磁场限值;并对根据工频磁场抗扰度严酷要求研制的用于云数据中心信息存储的服务器进行了工频磁场抗扰度测试。结果表明,当控制云数据中心与变电站强工频磁场源的距离10 m时,通信云数据中心的稳定持续工频磁场抗扰度和短时工频磁场抗扰度的磁场强度分别取100A/m和1 000 A/m;此外,通过改善信息存储设备耐受工频磁场的特性,可以取消云数据中心建筑物的工频磁场屏蔽措施,节省巨额屏蔽费用。所研制的服务器能够耐受与变电站共站的云数据中心可能出现的最为严酷的工频磁场环境。     

基于三维GIS的无人机巡检航迹规划研究

目前多旋翼无人机已在电力系统巡线中得到了广泛应用,结合无人机航迹规划研究现状,提出基于工频电磁场干扰研究的三维GIS无人机巡检航迹规划系统,通过建立导线对无人机工频电场和工频磁场干扰仿真模型,计算工频电磁场对无人机机身及机载设备影响,确定了安全飞行最小安全距离,并以确定的最小安全距离、线路杆塔三维模型及巡检任务相关信息实现在三维GIS上的无人机巡线路径规划、航迹跟踪和手动导航等功能,通过现场实际应用验证了航迹规划对巡检工作的重要性。     

500kV变电站站内工频电磁场检测分析

结合目前电力行业工频电磁场的检测判定标准,对广东省2座500 kV变电站站内工频电磁场进行检测分析,得出站内存在工频电场和工频磁场的结论。从保护变电站运行人员和公众免受低频电磁场影响的角度出发,提出相应的防护建议及措施。     

电磁场测试仪的应用效果评价

公众对变电站和线路工频电磁场的投诉依据,大多是基于利用简易电磁场测试仪对变电站和线路周围的工频电磁场进行测试的结果,而采用简易电磁场测试仪和标准规范中规定的常规电磁场测试仪的测试结果有较大差异。为此,评价了8种简易电磁场测试仪的性能,并在变电站和线路周围的电磁环境进行了实地测试,发现简易电磁场测试仪同常规电磁场测试仪的测试结果有较大差异,即:工频电场的检测结果最大相差近1倍,工频磁场的检测结果最大相差15倍;不同型号的简易电磁场测试仪间的测量结果也存在较大差异,工频电场的检测结果最大相差1倍,工频磁场的检测结果最大相差14倍。因此,对于简易电磁场测试仪的测量结果应该持谨慎态度,准确的工频电场强度和工频磁感应强度需要用常规电磁场测试仪进行测量。     

3种典型220kV GIS变电站进线方式的电磁场分析

高压输变电系统产生的工频电磁环境成为当今人们关注的热点问题。本研究利用COMSOLMuhiphysics（多物理场有限元仿真软件）,模拟分析了3种典型220kVGIS（气体绝缘组合电器设备）变电站进线方式在周围空间所产生的工频电场和磁场分布特征及影响规律。首先建立3种输电线路的模型;然后利用有限元法进行软件仿真,计算电磁场在离地1．5m和15m高度处的水平分布;最后按照国际非电离辐射防护委员会（ICNRIP）1998年发布的《限制时变电场、磁场和电场磁暴露（300Hz以下）导则》对结果进行评估。计算结果表明,220kV电压等级的3种进线方式产生的工频电磁场均低于ICNRIP规定的公众暴露限制。     

10 kV空心电抗器周围工频磁场的简化计算及影响范围

10 kV空心电抗器是110 kV和35 kV变电所中重要的工频磁场源。现有的空心电抗器周围工频磁场的计算方法需要电抗器的详细设计数据,而这些数据通常是制造商的技术秘密。笔者采用只需电抗器的铭牌参数和外形尺寸的简化方法分析10 kV空心电抗器周围的工频磁场分布。并用该方法分析电抗器的设计、布置等对周围磁场水平的影响。根据相关标准限值对这种电抗器的工频磁场暴露和干扰影响范围给出了定量的评价,可供变电所设计时参考。     

电力电缆线路的电磁环境影响因子分析

近年来电力电缆线路在城市输配电网中占有的比例越来越高,人们对电力电缆的电磁环境问题也逐渐开始关注。在参照架空输电线路电磁环境特性及其影响因子的基础上,结合电力电缆本身的特点,对其主要电磁环境影响因子(工频磁场)进行了模型建立和算法研究,并对3种典型分布的电力电缆工频磁场强度做了仿真分析,结果表明三相线路三角形排列能够较大程度地减小地面磁场强度。最后测试2条实际电力电缆线路的工频电磁场,其工频电场强度基本为背景值,符合理论分析;所测工频磁感应强度水平也在现行国家标准规定的磁场曝露限值要求以内。     

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.     

输电走廊工频电磁场的测量和解决方案

随着超高压电网的迅速发展,输电线路走廊的电磁辐射问题引起越来越多的关注.结合工程实例—某500 kV交流线路靠近小学校园引起师生身体不适,运用模拟电荷法和模拟电流法,分别分析了该线路走廊的工频电场和工频磁场的空间分布特性.同时,现场测量数据表明:在晴朗天气条件下,教学楼顶部分区域的电场强度接近国标限值;在阴雨(湿度较大...     

深圳地区220 kV输电线路工频电磁场效应问题

针对市民对深圳市区220kV输电线路的“电磁辐射”的投诉,实测和分析了220kV输电线路及变电站电磁场强度,结果显示,工频磁场测量值为0．01283mT,远低于国家标准的0．1mT,电场强度不超过国家规定的居民区工频电场评价标准4kV／m,该输电线路的工频辐射能量非常小,其辐射性质很弱,与国际上普遍认为工频电磁场对人体健康没有危害的认识一致。     

Evaluation and measurement of magnetic field exposure over human body near EHV transmission lines

Power frequency (50/60 Hz) magnetic field exposure still draws the attention of many researchers worldwide to investigate its harmful effects on living bodies. In light of this attention, as the population increases, the overlap between the power transmission lines and the settlement areas causes a problem (as in the case of exposure in random, residential, commercial and other areas, which lie very near or under the power transmission lines). In this paper, the power frequency magnetic fields, over a human body, at different positions, near extra high voltage (EHV) transmission lines are demonstrated, both analytically and practically. For the analytical part, the human body is approximately simulated as a parallelepiped. Two different positions for a human are selected near 500 and 220 kV power transmission lines. The magnetic field intensity along the vertical center line of the human is calculated. The effects of two different line configurations (for 220 and 500 kV power systems) and human positions, with respect to the transmission line, are considered. The paper also presents the actual practical magnetic field values measured near actual power transmission lines (220 and 500 kV) using a magnetic field measuring instrument. These transmission lines represent parts of the transmission network of the Egyptian united power system, near Cairo and El-Asher of Ramadan, under the actual loads. The results obtained, from the analytical studies and practical measurements, are compared with the international standards of the magnetic field exposures.     

Electromagnetic Environmental Impact of 500-kV Double -Circuit Transmission Lines

The strength of the power frequency electric intensity and magnetic field of the 500-kV double circuit transmission lines was calculated by using the equivalent charge method and the Ampere’s Law, and the environmental impact factors of the fields were evaluated. By optimizing the phase sequence, the frequency electric intensity and magnetic field strength can be reduced. Within a distance of 25 m from the center of the transmission line, the power frequency electric intensity and magnetic field strength fall off sharply with the distance increase. Finally, the best phase sequence and the minimum ground clearance of the transmission lines were obtained to meet the requirements of the least impact on envionment.     

Electric and magnetic fields

Increasing electrification brings increased human exposures to electric and magnetic fields, commonly called EMFs, and growing evidence suggests that exposure to even low frequency, low energy, electric and magnetic fields may be related to adverse health effects. This paper focuses on magnetic fields and strategies that address them. The challenges faced by scientists in understanding magnetic field interactions with humans, and of mitigating their effects, are discussed. The management of magnetic fields created by power systems are discussed including shielding and interference technology     

500 kV双回输电线路转角塔附近屋顶畸变电场分析

同塔双回输电线路转角塔附近的民房屋顶空间工频电场畸变严重,是制约输变电工程规划、设计和环保评价的重要因素。文中建立了500 k V双回输电线路转角塔附近空间工频电场的仿真模型,通过仿真计算与实测数据对比验证了模型的有效性,分析了影响屋顶电场畸变的因素,并按电场曝露限值标准推算房屋距线路的安全距离。研究表明,房屋距离线路的三维距离越近,电场越集中,房屋屋顶的曝露场强畸变越严重。房屋高度对电场的影响随距离增大而减小。最后给出了不同线路转角情况下转角塔附近不同高度房屋的安全距离,可为500 k V双回输电线路的工程规划、设计和环境影响评价提供参考。     

Determining EHV transmission line magnetic fields by applying the vector magnetic potential concept

These days renewed attention is being given to the biological effects of non-ionizing radiations from the power frequency electromagnetic fields of extra-high-voltage (EHV) transmission lines. Prior to fixing limits about the safe levels of human exposure to such radiation, it is essential to determine its field magnitudes. In this paper the concept of vector magnetic potential has been extended for a multiphase multiconductor transmission line and expressions for the flux densities of the resulting magnetic field components have been developed. This approach for determining the transmission line magnetic fields quantitatively is new and straightforward. It requires only easy-to-obtain physical parameters having specific values and involves no uncertainty. The proposed approach was applied to determine the magnetic field distribution within and beyond the rights of way of five transmission systems at 132, 230, 345, 500 and 765 kV. The results obtained were in close agreement with the measured field values. The proposed approach is expected to be useful for transmission line designers as a convincing and fast analytical tool for designing the allowable line current magnitude, conductor height and spacings, and number of circuits in order to result in a prespecified magnetic field. However, the results reported herein are expected to benefit researchers engaged in assessing whether magnetic fields of the orders of magnitude obtained for various transmission systems can have any adverse effects on the health of living beings exposed to the lines.     

Evaluation of magnetic induction inside humans at high voltage substations

The exposure to power frequency magnetic fields including those resulting from electrical power substations is playing a vital role in the human biological study. This paper presents a thorough investigation into the evaluation of the internal induced electric fields and induced current densities that are induced inside the human body due to the exposure to the external magnetic fields produced by a conventional 220/66 kV power substation.The effects of different parameters such as human location, human dimensions and the incident angle of the external magnetic field on the induced electric fields and current densities inside the human body are considered, through the theoretical cases. On the other hands, a typical case is presented to account for the induction levels over the human height due to external magnetic fields corresponding to the actual measured values at different locations in the substation.