Inspection of the efficiency of conductive clothing examination

High voltage live-line maintenance (LLM) is a commonly applied method worldwide to execute planned works in the grid economically [1]. In case of bare-hand technique workers wear a so-called conductive clothing acting as a Faraday-cage which protects them against the high electric fields during the work.     

Comparison of methods for determining corona inception voltages of transmission line conductors

Corona inception voltages are important parameters for power transmission-line conductors. However, there is no specific criterion for the determination of the corona inception voltage on such conductors. A corona cage is an effective and economical means for testing transmission-line conductors as it allows the duplication of surface electric fields, and hence the corona phenomena, at lower conductor voltages. Measurements with an ultraviolet imager, a partial discharge detector, a current-measuring radio-frequency interference receiver, and a sound level meter were used to observe the transition region between no corona and strong corona and hence determine the corona inception voltages of two practical conductors, types LGJ500/35 and LGJ400/50. Good agreement was found between the four approaches. The corona inception voltage was also calculated from first principles after determining the electric field near the surface strands using a charge simulation method, and compared with the peak inception voltages found from the measurements. Comparison was also made with the values obtained be applying Peek's equation. In both the calculations, Peek's surface roughness factor ‘m’ was applied with a value of 0.81 giving close agreement with the measurements.     

Induction charging risk assessment: Charged board alike discharges to metal and human body

Charge can easily be induced on electronics or on other conducting parts if they are exposed to external electrical fields. In production facilities where sensitive electronics are handled, strong electrostatic fields should be avoided due to the risk of causing electrostatic discharges (ESDs) that could damage components. In electronics manufacturing this is usually achieved by grounding all conductors and removing all insulators from an ESD Protected Area (EPA) in the facility. However, it is not always possible to remove all insulators from the EPA as they are sometimes an essential part of the production processes. In this case, a method of risk assessment is necessary to evaluate safe operation. We have studied induction charging of a dummy PWB (Printed Wiring Board) through a grounded MOSFET transistor, by grounding it directly to metal or through the human body, when the PWB is exposed to a static electric field. The experimental setup can easily be turned into an induction charging probe by changing the MOSFET transistor to a low leakage current, high voltage capacitor of suitable size and measuring the voltage over this capacitor.     

Effect of pollution severity class and service year on corona characteristics and electromagnetic environment degradation of aged conductors

Corona discharge and electromagnetic environment on AC long-term operated conductors are important issues for extra-high-voltage transmission lines. To investigate the relation between conductor age and electromagnetic environment, including audible noise and radio noise, several groups of long-term operated conductors in China are selected for corona cage experiment. According to corona tests, corona discharge becomes more serious as the applied voltage improves. Difference of electromagnetic environment between conductors of different operated year increases. Corona discharge and electromagnetic noise become more serious as the service year lengthens. When the operated years are close, the general environment is important in electromagnetic environment degradation.     

多芯屏蔽电缆电容的矩量法求解

 介绍了基于电压积分方程的矩量法计算具有圆形截面多导体传输线电容的基本原理,给出了三例屏蔽单芯或多芯电缆电容参数的计算结果,计算结果显示SYVZ-9电缆相邻导线间存在电容耦合,不相邻导线间几乎无电容耦合。     

Measurements of atmospheric potential gradient fluctuations caused by corona ions near high voltage power lines

High voltage power lines produce corona ions which can create disturbances in the Earth's vertical potential gradient. It has been hypothesised that these ions mediate adverse health effects such as the observed increase in leukaemia near to power lines. A fixed site monitoring station has been installed near two high voltage power lines which measures the vertical potential gradient throughout the year in all conditions. Ten minute samples of time varying potential gradient are sorted by wind direction to indicate whether the monitoring station is downwind of a power line and assessed for its variability by calculating mean, inter-quartile range and the number of turning points. Mean and inter-quartile range are related to wind direction, showing higher values when the wind is coming from the power lines.     

雷电电磁脉冲对架空电力线的耦合效应

 从传输线模型出发,通过建立雷电回击通道、大地和电力线系统一体化模型,采用时域有限差分法计算得出雷电回击电流的近场分布,将场值代入离散的传输线方程后,计算了架空电力线终端的感应过电压。通过对多导体架空线和单导体线终端感应过电压的分析,发现由于其它导体的存在,多导体系统中单根导体两端的感应电压峰值比相同高度处单一导体两端的感应电压峰值低10%～20%;并且对于垂直导体结构,最小感应电压产生在距离地面最近的导体上;而对于水平导体结构,最小感应电压产生在中间导体上。     

Erasable Ferroelectric Domain Wall Diodes

The unipolar diode-like domain wall currents in LiNbO3 single-crystal nanodevices are not only attractive in terms of their applications in nonvolatile ferroelectric domain wall memory,but also useful in half-wave and full-wave rectifier systems,as well as detector,power protection,and steady voltage circuits.Unlike traditional diodes,where the rectification functionality arises from the contact between n-type and p-type conductors,which are unchanged after off-line production,ferroelectric domain wall diodes can be reversibly created,erased,positioned,and shaped,using electric fields.We demonstrate such functionality using ferroelectric mesa-like cells,formed at the surface of an insulating X-cut LiNbO₃ single crystal.Under the application of an in-plane electric field above a coercive field along the polar Z axis,the domain within the cell is reversed to be antiparallel to the unswitched bottom domain via the formation of a conducting domain wall.The wall current was rectified using two interfacial volatile domains in contact with two side Pt electrodes.Unlike the nonvolatile inner domain wall,the interfacial domain walls disappear to turn off the wall current path after the removal of the applied electric field,or under a negative applied voltage,due to the built-in interfacial imprint fields.These novel devices have the potential to facilitate the random definition of diode-like elements in modern large-scale integrated circuits.     

重复高压脉冲产生与成形一体化装置研制

 介绍了脉冲变压器与分布参量形成线相结合的高功率脉冲产生与成形一体技术,简要阐述了采用该技术的高压脉冲发生器的基本设计思想。研制的脉冲变压器与形成线一体化装置利用变压器的同轴开环铁芯来充当分布电参量脉冲形成线的内外导体,将脉冲功率源中最重要的两个独立部件有机结合起来,实现了结构的紧凑性。高压脉冲发生器在重复频率100 Hz、变压器工作电压1.65 MV时能够稳定运行,输出脉冲电压760 kV,峰值功率23 GW,脉冲宽度大于40 ns。     

脉冲波沿多导线传输系统传播的矩阵分析

本文从电压和电流的基本方程出发,分析脉冲波在多导线传输系统的传播现象和多导线传输系统导线间的相互耦合作用。分析结果说明,在一轮换的双迴三相输电系统里,系统扰动将会产生四种不同速度的脉冲波,对这四种不同速度的脉冲波将有四个不同的特性阻抗。应用这些关系,将能解释线路上脉冲波传播的某些特殊现象,和按照给定的边际条件计算出波的畸变、反射和折射等等,从而对线路实测结果提供理论依据。文中举例说明这分析方法。这脉冲波传播的理论分析被进一步推广应用到稳态交流运行情况,并推导出双迴输电线的等效电路。     

Vibrations of narrow microbeams predeformed by an electric field

Vibrations of a fixed–fixed narrow microbeam electrostatically actuated by applying a voltage difference to it and a parallel rigid conductor are analyzed. For gaps between the two conductors that are comparable to the beam's thickness, the fundamental frequency of the beam may first increase with increasing applied voltage, before suddenly dropping at the pull-in voltage. Available models fail to accurately describe this behavior of the frequency versus voltage diagram for narrow microbeams, that results from a combination of strain-hardening and electrostatic softening effects. A distributed electromechanical model, that accounts for electrostatic fringing fields, finite deflections and residual stresses, is proposed. A recent estimate of the electrostatic force incorporating fringing fields due to both finite width and finite thickness of the microbeam is employed. The lowest frequency is extracted with a simple and computationally efficient one degree-of-freedom model obtained by approximating the deflection field with the static deflection of a fixed–fixed microbeam loaded by a uniformly distributed force. The model's predictions are in good agreement with those from three-dimensional finite-element simulations.     

Single-phase AC losses in prototype HTS conductors for superconducting power transmission lines

We report single-phase AC loss measurements on 8-, 4-, and 3-layer, multi-strand, HTS prototype conductors for power transmission lines. We use both calorimetric and electrical techniques. The agreement between the two techniques suggests that the interlayer current distribution in 1-m long conductors are representative of those in long conductors. The losses for the 8- and 4-layer conductors are in rough agreement, with the 8-layer losses being somewhat lower. The 3-layer conductor losses are substantially higher — probably due to unbalanced azimuthal currents for this configuration.     

非线性传输线高功率实验北大核心CSCD

设计了基于交叉耦合铁氧体非线性传输线高功率射频微波产生系统,系统由脉冲形成线、非线性传输线以及高功率匹配负载(或组合振子辐射天线)组成。由100kV高压电源和高压微波电缆构成单传输线高功率脉冲形成线,形成线输出脉冲幅度35kV,脉冲半宽60ns。高压脉冲经过非线性传输线的脉冲压缩和调制,与高功率匹配负载相连时,实验得到了峰峰值31kV、中心频率308 MHz、3dB带宽为13%的射频振荡脉冲;与组合振子天线相连时,实验得到了中心频率380MHz、3dB带宽为12%的宽谱辐射。实验结果与数值模拟基本吻合。     

Magnetic field effects in proteins

ABSTRACT

Many animals can sense the geomagnetic field, which appears to aid in behaviours such as migration. The influence of man-made magnetic fields on biology, however, is potentially more sinister, with adverse health effects being claimed from exposure to fields from mobile phones or high voltage power lines. Do these phenomena have a common, biophysical origin, and is it even plausible that such weak fields can profoundly impact noisy biological systems? Radical pair intermediates are widespread in protein reaction mechanisms, and the radical pair mechanism has risen to prominence as perhaps the most plausible means by which even very weak fields might impact biology. In this New Views article, I will discuss the literature over the past 40 years that has investigated the topic of magnetic field effects in proteins. The lack of reproducible results has cast a shadow over the area. However, magnetic field and spin effects have proven to be useful mechanistic tools for radical mechanism in biology. Moreover, if a magnetic effect on a radical pair mechanism in a protein were to influence a biological system, the conditions necessary for it to do so appear increasing unlikely to have come about by chance.     

高压交流输电线路故障检修技术研究

对高压交流输电线路故障检修技术进行研究,可以提高电力质量,减少因线路故障产生的一系列人财有损情况的发生。当前方法将短期的输电线路检修当作单重不确定性的优化问题,对其进行建模以及求解。而在现场运行过程中,架空线路可靠性指标不能准确表达线路故障发生的可能性,其理论基础相对薄弱,仅考虑了单重不确定性的问题,无法对高压交流输电线路进行高精度地检修。为此,提出一种基于层次分析的高压交流输电线路故障检修方法。该方法先将高压交流输电线路故障划分为：单相接地故障、高压交流输电线路短路故障、高压交流输电线路导线断路故障。然后利用多个电流测量点,通过FFT程序对电流故障分量相位进行求解,根据比较相邻测点相位差判别故障区域,最后利用图论实现高压交流输电线路故障检修时间控制函数,以及线路故障检修经济控制目标函数的制定,与分类和定位结果结合完成高压交流输电线路故障的检修。实验结果证明,所提方法可以有效地对高压交流输电线路故障进行检修,具有一定的利用价值。     

腔体内传输线耦合的电磁仿真软件与传输线方程的混合算法

研究了一种有限积分法软件与传输线方程相结合的混合算法,用于解决复杂电磁环境下屏蔽腔体内传输线的电磁耦合问题。利用有限积分法软件实现屏蔽腔体的建模,仿真得到腔体内部空间电磁场分布,并设置电场探针提取出传输线的激励场。利用传输线方程建立腔体内传输线的耦合模型,将得到的传输线激励场引入到传输线方程作为等效分布电压和电流源。利用时域有限差分(FDTD)格式对传输线方程进行离散,从而迭代求解出传输线终端负载上的电压和电流响应。通过与文献以及传统数值算法的计算结果进行对比,验证混合算法的正确性。研究表明,该混合算法在模拟电大尺寸腔体内传输线的电磁耦合方面,具有较高的精度和计算效率。     

Engineering of solid state ionic devices

Solid state ionic devices such as high performance batteries, fuel and electrolysis cells, electrochromic devices, chemical sensors, thermoelectric converters or photogalvanic solar cells are of tremendous practical interest in view of our energy and environmental needs. The challenges are the achievement of higher energy and power densities, longer lifetimes, cheaper materials, lower cost, improved sensitivity and higher stability. The engineering of new devices is based on the better fundamental understanding of materials for galvanic cells and their interaction in order to approach solutions more systematically than in the past. The fundamental aspects of the generation of voltages and electrical currents are compiled and analysed in view of the materials requirements. Conflicts exist in forming chemically stable interfaces of functionally different electrolyte and electrode materials, achieving simultaneously high energy and power densities in view of low conductivities of chemically stable materials, fast chemical diffusion in electrodes which should have a wide range of non-stoichiometry for delivering and absorbing the mobile ionic species, practical problems of using less expensive polycrystalline materials which have high intergranular resistances and finally reaching both ionic and electronic equilibria at the electrolyte - electrode interfaces at low temperatures. The engineering of new or improved solid state ionic devices is commonly based on individual materials considerations and their interaction in galvanic cells. Simultaneously high ionic conductivity and chemical stability may be reached by designing structures of poly-ions of the non-conducting components with the conducting species in-between. The chemical stability may be based on kinetic restrictions for sufficiently long periods of time of operation of the devices. Electrodes should not be made of metallic conductors but of electronic semi-conductors with fast enhancement of the diffusion of ions by internal electrical fields. Device considerations are based on the development of single element arrangements (SEAs) which incorporate the electrodes into the electrolyte in the case of fuel and electrolysis cells. The electronic conductivity is generated by the applied gas partial pressures or the applied voltage. The same simplification may be applied for electrochromic systems which consist of a single active layer instead of the conventional three galvanic cell materials. A new design of active chemical sensors probing the environment by the magnitude of the applied voltage or current may overcome the limitations of cross sensitivities and interfacial reactions which allows the simultaneous detection of several species by a single galvanic cell. The paper has been prepared for presentation at the International Conference on Ionic Devices — 2003, Anna University, Nov. 28–30, 2003, Chennai, India.     

Skin effect in massive conductors used in pulsed electrical devices: II. Massive conductors in electric circuits

Approximate relationships between the current and voltage drop across a set of massive conductors are established. They include two constant parameters: external inductance L of the conductors and skin parameter S. Specific shapes of the voltage across the massive conductors are illustrated with oscillograms. Mathematical processing of current and voltage oscillograms to estimate L and S is developed.     

Development of YBCO power devices in Japan

A new Japanese national project, called M-PACC, to develop high temperature superconducting electric power devices started in June last year (FY2008–FY2012). This project aims to develop three different types of electric power devices that are expected to provide stable power supplies with large capacity and small size by using YBCO coated conductors. The first program is the development of a 2 GJ class superconducting magnetic energy storage system to control stable electric power systems. It is planned to develop several sets of element coils for a 20 MJ class system as a technological feasibility study for a 2 GJ class coil. The second program is the development of two different types of power cables with higher performance than existing power cables; one is a three-core 66 kV–5 kA class large current cable and the other is a single-phase 275 kV–3 kA class high voltage cable. These cable were required several technological developments, namely, large current and low AC loss, high voltage insulation and low dielectric loss, and power and heat balance for both cables. The third program is the development of a 20 MVA class power transformer with 66 kV/6.9 kV as a distribution transformer. In this project, power transformer systematization technology including 2 kA class large current coil technology, anti short-circuit wire winding technology, AC loss reduction technology, and winding technology will be developed.     

Tesla-PFN型长脉冲功率源加载线的结构设计

 为解决Tesla-PFN型长脉冲功率源在高电压下多个加载线串联时加载线之间出现的电磁干扰问题,对一种环形串联加载线的结构进行了优化设计,重点解决了加载线与形成线的阻抗匹配及加载线的高压绝缘问题。优化了过渡段结构,使形成线与加载线阻抗匹配较好,输出脉冲顶部平坦;利用静电场分析软件计算了加载线的电场分布,通过调整屏蔽环的形状和位置使电场分布更加均匀。