Simplified Method for Calculation of Current Distribution on Grounding Electrodes

A new method is presented to calculate the non-uniform of current distribution on grounding electrode. Based on the equivalence of low frequency current field and static electric field, the electrode is simplified to he a line charge model with limited length. The charge distribution on the model is calculated by solving equilibrant equations, and the current distribution along the axis of electrode was got. The current density at the end of electrode can he several times of that in the middle, the non-uniformity get worse with the increasing of electrode length and numbers. This is what lead to several problems on grounding systems such as inefficiency, the partial overheat and the severe corrosion of electrode.     

Shunt Active Power Filiter for Harmonic Compensation in DC Side of HVDC Transmission System

A shunt active power filiter(APF) used for harmonic treatment isintroduced in this paper. Basic circuit-theory and main configuration are analyzed. Control scheme and its realization are discussed. Computer simulation is used to verity theoretical analysis. It shows that APF is an interesting alternative for hasmonic treatment compared with conventional passive filter.     

Influence of HVDC System on the Shaft of Hydro-generator Unit

Widely concerns of the influence of the HVDC system on the Three Gorges power station have been shown so far. Based on the understanding of the mechanism of the non-characteristic harmonics introduced by HVDC system, the influence of interharmonics on the shaft of hydro-generator unit is studied. A MATLAB simulation model for the Three Gorges hybrid AC and DC transmission system with considering the effect of generator-unit shaft is established. Through time-domain simulation, the influence of the minor-associated component of interharmonics on the generator-unit shaft is analyzed, which arise from the asynchronous operation of the HVDC system. Also, the complex torque coefficient method in frequency-domain is used to analyze this problem. Same conclusions can be drawn from the results of timedomain and frequency-domain analyses.     

A Hybrid Filter Composed of Shunt Passive and Series Active Filter on DC Side in HVDC System

For requirements of suppressing harmonics on the dc side of HVDC system,a new hybrid filtering system a shunt passive and a small rated reactor transformer coupling series active filter is presented,and the harmonic compensation and control principles are discussed theoretically in this paper.Digital simulation results show excellent filtering characteristics of harmonic current and very high performance/cost by using a new hybrid filtering system proposed int this paper.     

The Theoretical Expression of Carbon Potential for Carburizing Atmosphere and Its Exact Measurement

The paper deals with the signification of carbon potential and its influencefactors. The exact expression of carbon potential has been deduced on the basis of reactionthermodynamics and masstransfer kinetics for carburization,and according to these a new methodto measure carbon potential quickly and exactly has been suggested.     

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.     

几种葡萄砧木的引种表现及抗寒性分析

旨在研究几种葡萄砧木的抗寒适应性。本试验以引进的1年生‘贝达’、‘山河1号’、‘SO4’、‘5BB’、‘抗砧3号’5种葡萄砧木为试材,进行植物学特性和生长特性调查,测定电导率、失水速率、萌芽率等指标,综合分析各砧木品种的抗寒适应性。结果表明,不同葡萄砧木叶片和新梢之间的形态特征表现不同;‘贝达’的新梢生长速率在各测定砧木中表现最高;‘抗砧3号’的移栽成活率和扦插成活率最低,分别为74%和79%,‘贝达’的移栽成活率和扦插生根率显著高于其他砧木,在新疆北疆地区具有较强的适应能力;综合评价各砧木抗寒性得出：‘贝达’＞‘山河1号’＞‘5BB’＞‘抗砧3号’＞‘SO4’。本研究结果为葡萄砧木利用及品种改良提供理论参考依据。     

Theoretical Analysis and Design of Resonant DC Base High Frequency Inverter

A theoretical analysis of the Resonant DC Base High Frequency Inverter is given. A optimal control scheme for the short circuit current of the resonant inductor is proposed. The system parameters,output current,output voltage and characteristics of the Resonant DC Base in this scheme are analysed. In the theoretical analysis the load is supposed as a resistor to void the calculating error while the load is treated as a constant current source. The analysis and test result have proved that the optimal parameters of the Resonant DC are only determined by the load resistance and the output frequency.     

Theoretical Analysis and Testing of Ground Treatment Using an Expansive Method in Very Thick Collapsible Loess

Through technological research of foundation treatments in the collapsible loess areas, we recommend a method of treating foundations in collapsible loess with quicklime piles. We set forth the basic principle of this expansive method. When a very thick foundation in collapsible loess is treated, the computational formula for the volume of expanding material in a quicklime pile is deduced based on cavity expansion theory. This theory is applied to engineering practice. Physical and mechanical properties of the compacted soil are tested. The result shows that the collapsibility of a foundation in loess has been eliminated, its physico mechanical indexes have been improved, and the soil compressibility and the modulus of compressibility also increase remarkably, demonstrating the correctness of the computation theory. The feasibility of the expansive method for very thick collapsible loess areas is further established.     

Comparative Analysis of Heat Exchange Performance ofEnergy Piles and Borehole Heat Exchangers in GSHP System

Due to their enhanced cost-effectiveness and efficiency over traditional borehole exchangers, energy piles are increasingly used in Ground Sourced Heat Pump (GSHP) projects. In this paper, the structural characteristics of these two types of heat exchangers and their heat transfer mechanism were discussed firstly. The thermal response tests (TRT) were performed on two testing energy piles in one GSHP project in Nanjing, China. The TRT results were then used to verify the numerical simulations, which suggests that the heat exchange performance of energy piles is superior to that of the traditional borehole exchangers. Meanwhile, the numerical simulation method used in this paper was considered applicable to the optimization design of ground heat exchangers in GSHP system.     

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.     

Using Agent Server to Enhance the Performance of Remote Data Service Based on HFC Network

The bi-directional Hybrid Fiber/Coaxial (HFC), which has almost 1GHz frequency bandwidth to transmit information, is the best access mode except Fiber to the Home (FTTH). Initial experiences indicate that real-world HFC networks are susceptible to a variety of radio-frequency impairments that significantly reduce the benefits of using high-speed cable modems. In this paper, the performance of data services in the TCP sub-layer of a HFC network is discussed and an agent server is used to enhance the performance of remote data transmission.[WT5HZ]     

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.     

基于传输线网络的特高压变电站智能组件端口电磁骚扰的建模仿真

随着智能化GIS设备的发展,GIS设备上集成了大量电子设备。GIS设备开关操作产生的特快速瞬态电磁过程主要经由“传感器—二次电缆—智能组件”这段电路对电子设备产生电磁影响。笔者首先基于传输线网络理论建立了开关操作产生的地电位升对“传感器—二次电缆—智能组件”回路的耦合计算模型,然后通过验证实验证明了计算模型的有效性和准确性,最后对不同屏蔽层接地方式下的各传感器端口和智能组件各端口及端口间的骚扰电压进行了仿真研究。计算结果显示,各骚扰电压受接地方式的影响较大;通过选择合适的接地方式,可以有效地抑制开关操作电磁骚扰。     

水分胁迫下蔗叶活性氧代谢的数学分析

水分胁迫加速了蔗叶活性氧的产生并消弱其清除能力。经回归模拟显示，蔗叶ＭＤＡ含量、质膜差别透性、Ｏ２＾－产生速率和组织自动氧化速率均随土壤含水量的降低呈指数增加，ＳＯＤ活性和ＧＳＨ含量呈抛物线变化，而ＣＡＴ活性呈对数降低；逐步回归分析定量地指出了水分胁迫下蔗叶ＳＯＤ和ＣＡＴ在清除活性氧、防止膜脂过氧化和质膜破坏中的协同作用关系，且受Ｏ２＾－产生的影响；经卡方测验证实，该回归模型各参数与大田干旱胁迫的     

Modeling and Performance Analysis of Unglazed Solar Collector/Regenerator

An analytical model of the unglazed solar collector/regenerator(C/R) was presented. There was an optimum flow rate per unit collector area at normal temperature which led to the maximum evaporation rate. The inlet temperature of absorbent solution and the wind velocity are key parameters to determine the optimum flow rate, in addition, the concentration of solution and solar radiation intensity have obvious effects on the maximum evaporation rate. When the outlet temperature of solution is higher than the inlet temperature, there is not an optimum flow rate, which reflects that the more the flow rate of solution is, the better regeneration efficiency is. With the 2m/s of wind speed, the evaporation rate reaches the peak. In this paper, kinds of factors influencing the performance of solar C/R were evaluated as well.     

The Research of the Mathematical Relationship Between RC Electrical Network and Viscoelasticity

The duality principle in electrical network was generalized to establish the one to one correspondence between generalized linear viscoelastic model and RC electrical network.On this basis,a guess was proved to be true that any generalized linear viscoelastic model with arbitrary complexity can be simplified as generalized Voigt chain equivalently.