Lightning Shielding Simulation Model of Transmission Line

Transmission lines are easily hit by lightning, and lightning shielding failure is an important reason of lightning accidents of transmission line. So researches on lightning shielding of transmission line should be strengthened. On the basis of the abundant understand to known lightning shielding models of transmission line, a new lightning shielding simulation model of transmission line is presented in the paper. In this model, the effect of attracting lightning of upward leader is considered reasonably, and the method of variable descending step is adopted to simulate the descending process of lightning leader. The simulation calculating results show that the model is in good agreement with field experience of transmission line. It can guide lightning shielding design of transmission line and estimate the performance of lightning shielding of transmission line.     

Analysis on the Lightning Protection Performance of 500 kV Double-circuit Transmission Line

Using double-circuit transmission line is the developing tide for main 500 kV configuration to reduce line holding ground, so analyzing it's lightning protection performance is important to extend double-circuit transmission line in ultra high voltage network. The lightning protection performance of 500 kV double-circuit transmission line is studied with EMTP and EGM. The statistical method is applied to analyzing the lightning protection performance of back stroke by considering the randomness of working voltage's phase when lightning stroked the top tower. The result is that the line lightning protection level is different when the working voltage of conductor is different. It also improved the EGM by considering the effect of wind speed when analyzing the lightning protection performance of shielding failure. Furthermore, the results are given that wind speed has effects on the protection angle and the rate of shielding failure by using the program to calculate it.     

Model and Numerical Analysis of Radiation Field Created by Lightning Overvoltage Wave on Transmission Lines

The radiation field created by the transmission line stroked by lightning far from the lightning channel has been analyzed by the FDTD method.The authors we establish the calculation model and FDTD calculation method of transmission line,and discusses the import of lightning excitation source.The simulation of lightning stroked on a single transmission line in free space or stroked on three-phase high voltage transmission lines in actual environments has been done,and gives the distribution of transient radiation field around the transmission lines when lightning overvoltage wave transmits along the transmission line.The simulation result shows that: the effect of the transient radiation field caused by lightning over voltage wave done with environment is obvious,and the high frequency component of transient radiation field may disturb or do harm to the electronic facility or communication facility around the transmission lines.     

Analyze the Present Status in the Calculation Methods of Lightning Protection Performance for Transmission Line

Lightning is the main reason that endangers transmission line working safety and reliabilty today. The theory and characteristic of methods that not only estimate the lightning performance for back strike such as standard method, traveling wave method, Monte Carlo technique, treeing fault method, EMTP and so on but also for the shielding failure such as standard method, EGM, leader progression model and so on are summarized. The criterion of flashover for insulators is referred simply, furthermore, it gives the opinion that the development of research for the future.     

Lightning Proof Performance of 500 kV Transmission Line in Chongqing Area

Considering the importance of 500 kV line and taking 500 kV transmission line in Chongqing as an example, the authors calculate lightning strike outage rate (including return stroke and lightning shielding failure) using regulation method, outage rate of return stroke using travelling wave method, and outage rate of lightning shielding failure using EGM. By comparing and analysing the calculating fesults, weakness of insulation and the area of easy to striking are found out, and corresponding improving measure is brought forward. The results show bigger gradient of lightning higher return stroke tripping, and in regulations result of accounting return stroke tripping is more closed to practical experience, accounting shielding failure rate exists obviously defect, and in EGM accounting shielding failure rate have take much factor, result is more close to practical experience.     

基于VLF/LF三维闪电探测系统的贵州省全闪分布特征分析

为进一步加强云闪分布特征分析,增强对雷暴云内物理过程的认识,利用2015—2017 年VLF/LF三维闪电探测系统的数据资料对贵州省闪电特征进行空间和时间分布特征分析。结果表明：无论云闪还是地闪,均以负闪为主;闪电发生主要集中在夏季,冬季闪电最少,闪电月际分布主要为单峰型,仅冬季Z比率大于1;闪电主要发生时段为16 时至次日凌晨2 时,Z比率与全闪频数随时间的变化呈正相关,相关系数0.618;全省闪电密度整体呈西高东低趋势,年均闪电密度为5.07 次/(a ·km2);云闪主要发生在高度2k~7 km,全年云闪高度呈下降趋势;雷电强度主要分布在5k~45 kA,平均陡度为7.34 kA/μs。本研究有利于对闪电特征开展更全面的探究和分析,同时对强对流天气监测和预警也有重要意义和价值。     

雷暴天气下建筑物周围电场畸变区域的研究分析

为了探究在雷暴发生时建筑物周围电场畸变区域的规律,利用Integrated Engineering Software电磁暂态仿真软件,模拟分析雷暴云及建筑物结构对周围电场畸变特征的影响。结果表明：当雷暴云过境时,群体建筑物遭受雷击的概率会减小,这主要是因为群体建筑物之间的屏蔽效应,改变了周围区域的电场畸变程度,降低了产生上行先导的概率和遭受雷击的概率。对于单体建筑而言,当雷暴云过境时,建筑物周围电场畸变区域呈半球形状,电场的畸变程度与建筑物的高度呈线性相关,高度越高,畸变区域越大,将导致前方流注扩展的区域变大,从而增加了下行先导发生的概率,这也是越高的物体易遭受雷击的原因。     

The Influence of Beam Column Stiffness Ratio of Mine Shaft Tower to Shear Lag Effect

Making use of large finite element analysis software ANSYS, combine with the mine shaft tower actual frame tube structure project to model analysis, by means of concrete performance of mine shaft tower under the effect of horizontal load, come to a conclusion that beam column stiffness ratio has a great influence on shear lag effect. Then analyse the phenomenon of beam column stiffness ratio to shear lag effect, make a comparison on calculated results and simulation analysis results, to move an improved method. It has a great guiding significance for the mine shaft tower structural design.     

Computerized Simulation of the Transmission Line in High-speed PCB

With the rapid development in logic circuit,the effect of transmission line in PCB becomes a confined factor.In the design of high-speed PCB,the factors which affect the integrity of signal can be found by computerized simulation of the transmission line,simultaneously the signal quality could be optimized.The capacitance matrices of transmission line in high-speed PCB have been computed with this method that is the total charge Green's functions with method of matrix,then the time-domain model is built.Connected to IBIS model of the I/O buffer these models can be used in computerized simulation of the transmission line.The result of simulation is equal with the result produced by EDA software-Specctraquest of cadence Co.and the efficiency of simulation is advanced.     

Construction Technology for Bid Construction Part B of Yangtze River Bridge in Jiangyin City

In this paper, the advanced construction technology and site management applied in bid construction part B of Yangtze River bridge in Jiangyin was presented in detail. This bridge is the largest span bridge in China, where the advanced technology applied is: 3-d coordinate control surveying in bridge tower, small powder for artificial pile, over-form and climb form in construction of tower column, temperature control for casting mass concrete. It is of great value for reference to large bridge building.     

Development of a Novel Intellectual Transmission Line Inspection System

The power transmission line is one of the important parts of electrical power system,the management and inspection of the transmission lines have been significant routine job ensuring the reliability of the transmission system. This paper describes in detail the basic principle of the intellectual transmission line inspection system using Geographic Information System(GIS) and Global Position System(GPS) technology.This novel inspection system is composed of pocket PC,GPS receiver and management PC,and takes full advantage of modern computer and network communication technique.Owing to the advantages of high reliability,practicability and scalability,the practical application of this intellectual inspection system shows that it completely meets the requirements for fast speed,high efficiency and real-time performance.     

Simulation of ice shedding on transmission lines considering ice shedding velocity effect

Ice shedding on transmission lines results in longitudinal unbalanced forces on adjacent transmission towers,which significantly threaten the safety of transmission lines.The methodology of ice shedding simulation on transmission lines is developed by using the finite element method and validated by comparing the simulation results with those obtained from the model scale experiments done by previous researchers.The responses of the tower line system induced by simultaneous ice shedding on the conductor and ground wire are analyzed.The developed methodology is then applied to study ice shedding considering unzipping effect,in which the influence of the velocity of ice shedding on the responses is investigated.Results from this study show that the longitudinal unbalanced forces induced by simultaneous ice shedding from the ground wire are greater than those from the conductor under similar condition.During the analysis of ice shedding considering unzipping effect,the slower the velocity of ice shedding is,the closer the responses are to those resulting from static unloading;and the faster the velocity of ice shedding is,the closer the responses are to those resulting from simultaneous ice shedding.     

基于层次模型及权重分析的湖北省雷电灾害易损度区划

利用湖北省2008-2011年闪电监测数据和2000-2009年雷电灾害统计数据,选取雷击大地密度、大于50kA强雷击密度、雷电灾害频度、生命易损模数及经济易损模数作为湖北省雷电灾害易损性评估指标。提出了对雷灾频度因子的修正,只有把该参数放到同一起点比较,雷电灾害易损性分析及风险区划才具科学性,同时引入大于50kA强雷击密度作为雷电灾害易损性评估指标之一。采用层次模型及权重分析对雷电灾害易损性指标划分了5个等级,最后形成湖北省雷电灾害易损度区划。研究结果表明：高风险区的城市主要特征是雷灾频度较高、经济发展水平较好、人口密集;低风险区则与之相反。雷电灾害易损度不仅与单位面积上的雷电密度、雷灾频度关系密切,还与单位面积上的经济发展水平、人口密度息息相关。     

雷电灾害风险评估中P_B因子选取方法的分析及改进

在分析雷电直接击中建筑物导致物理损害的概率PB的影响因素的基础上,本文基于IEC62305推荐的不同防护等级的保护能力以及雷电流概率分布规律,推导出确定规范中LPL对应的PB因子优选值的一般过程。并针对推导过程完全依赖于规范推荐的防护等级及雷电活动特性,针对性差的特点,提出了根据建筑物直击雷防护实际情况以及项目所在位置雷电环境的统计特征确定PB因子的方法,该方法在一定程度上提高了PB因子选取的科学、准确性。同时,也对由于雷击物理过程复杂性、电气-几何模型的科学性、防护装置性能变化等使得PB因子取值中存在的问题进行了分析。     

基于GIS和AHP的雷电灾害风险区划分析与评估——以内蒙古雷灾为例

基于自然灾害风险理论,利用雷暴日和闪电定位资料、基础地理信息资料、社会经济资料以及雷电灾情资料,选取地形变化、水系、土壤电导率、雷暴日、地闪密度、土地利用、人均GDP、敏感单位防雷能力等11个指标,运用层次分析法构建了雷电灾害风险指数,建立雷电灾害风险评估模型,从雷电灾害的致灾因子、孕灾环境、承灾体和防灾减灾能力4个方面进行了系统的分析,并运用ArcGIS进行了1km×1km雷电灾害综合风险区划。区划结果表明内蒙古东部大部和中部南部地区属于高风险区,中部北部地区属于中风险区,低风险区域主要分布在西部地区。通过选取雷灾资料进行雷电灾害的灰色关联评估,以验证区划结果的正确性,评估结果与雷电灾害风险区划分布大体一致。     

中国农业上市公司绩效评价

农业是整个国民经济发展的基础,农业上市公司作为农业产业化的龙头,提高农业上市公司绩效对于农业发展具有重要的意义。本文先对27家农业上市公司2007、2008和2009年的财务数据进行移动平均,并运用因子分析法对所得结果进行绩效评价,得出了当前农业上市公司规模普遍较小、经营绩效呈“两头小,中间大”的橄榄型分布、各子行业发展不均衡的结论,并提出了提高农业上市公司绩效的政策建议。     

Vibration Analysis and System Simulation for a Stalled Wind Turbine

The aerodynamic characteristic of wind turbine is calculated by applying the Blade Element Momentum(BEM) theory.Also finite element mode analysis is done for the tower and the rotor.Then the multi-dynamic model of the wind turbine is built in Adams.Also the drive chain is calculated by applying state space method and programmed in Matlab/ Simulink.With that the combined simulation of vibration characteristics is carried out on the base of MATLAB/Simulink and ADAMS,in which the transmission effects and aero-elasticity coupling is fully considered.The results show that the method is able to simulate the vibration characteristic almost the same as software Bladed,which is well-known for analyzing performance and loads for the design and certification of wind turbines.     

菏泽市雷电灾害风险区划研究

为了明确不同县区雷电灾害风险的高低、防御和减轻雷电灾害,以闪电定位资料和经济社会资料为基础,采取归一化法、层次分析法、加权综合评价法,统筹考虑致灾因子的危险性、孕灾环境的敏感性、承灾体的易损性和防灾减灾能力4个评价指标,选择9个影响因子建立雷电灾害区划模型,绘制出菏泽市雷电灾害风险区划图。结果得出：曹县和东明是致灾因子危险性高值区,两地的孕灾环境敏感性同样较高,牡丹区和定陶是承灾体易损性高的区域,防灾减灾能力的高值区在牡丹区和东明。曹县和东明是雷电灾害的高风险区,次高风险区为单县和巨野,中等风险区为定陶,次低风险区为成武和郓城,牡丹区和鄄城由于防灾减灾能力强或致灾因子危险性较低划为低风险区。     

An optimal equivalent subchannel algorithm for low voltage power line communication system

According to the low voltage power line channel features,combined with adaptive bit loading and power allocation algorithm,an optimal equivalent subchannel algorithm is proposed.Under the condition of fixed amount of transmitted bits and the minimum transmitted power model,impact of optimal equivalent subchannel on the system performance is studied.The optimization algorithm sorts subchannels with similar transmission features into groups,thus the signaling load can be reduced,and the spectrum can be better used.The simulation results show that system can get lower bit error rate(BER) by adopting optimal equivalent subchannel algorithm.     

基于层次分析模型的云南省雷电致灾评价及易损性区划

根据2008—2017 年闪电定位监测和雷电灾害统计资料,分析地闪活动的时空分布规律,建立包含雷电风险、地域风险和承灾体风险的雷灾易损性综合评价指标体系,运用层次分析法(AHP)构建指标权重判断矩阵,得出易损性综合评价指数R 的换算方程并确定各州（市）雷灾易损性等级,形成云南省雷电灾害易损性风险区划。结果表明：昆明、玉溪地闪致灾因子活跃,雷灾易损性综合评价指数高,是雷电灾害极高易损区,受灾涉及行业及影响范围广;普洱、曲靖、丽江、楚雄、红河、西双版纳为雷电灾害高易损区,该等级区域所占比例最大,分布范围最广;保山、昭通、临沧、文山、大理为雷电灾害中易损区;迪庆、怒江、德宏为雷电灾害低易损区,通过加强雷电防御设施建设,扩大预警覆盖面,强化防雷科普宣传能够提高承灾体抵御雷击的能力。