Peculiarities of electromagnetic processes in a three-phase, three-level rectifier

The electromagnetic processes of a three-phase, three-level rectifier with a vector PWM are considered. The results are presented for the process analysis in the circuit at the point where the input current passes through zero. The best sinusoidal shape of the input current is shown to take place at the unit coefficient of the input current shift. The possibility of balancing the voltage at the output rectifier capacitors is also shown. Results are obtained from modeling in the Matlab Simulink environment.     

Numerical investigations of electromagnetic processes in a solid cylindrical shield

A mathematical model is suggested to describe the processes in a solid cylindrical shield in protection against an alternating magnetic field. The model is constructed with respect to the complex amplitude of magnetic vector potential. Since magnetic field lines are in a plane perpendicular to the axis of a cylindrical shield, the problem becomes two-dimensional. The electromagnetic parameters of the considered media are constant and isotropic. The plates at which the magnetic potential is set are the source of the magnetic field. A distribution of real and imaginary components of the complex amplitude of magnetic potential is described by four differential equations in the conducting medium and by two equations in the dielectric one. An equality of magnetic potential at both sides of the interface is predetermined at the interfaces. The Robin boundary condition provides equality of the magnetic vector potential to zero at an infinite distance from the shield. The obtained differential equation system supplemented with the boundary conditions can be numerically solved by the finite elements method using the Galerkin method. As a result, distributions of magnetic potential and magnetic field intensity in the absence and presence of a shield are determined; shielding attenuation is then calculated. It is found that, with increasing shield thickness and noise frequency, the efficiency of electromagnetic shielding is increased. The adequacy of the suggested model and technique of determination of the shielding efficiency is corroborated by comparison with the results of an analytical model for a copper cylindrical shield.     

交流架空线路导线电磁感应取能功率分析与研究

本文介绍了在智能电网背景下的架空线路在线监测装置对供电的需求特点,论述了当前交流架空线路在线感应取能的几种方式及其原理,重点对导线电磁感应取能技术进行了分析.通过导线电磁感应取能原理建立了取能的物理和电路模型,在对影响取能的各因素进行分析后,进行了该方式在特定取能条件下的最大功率估算,并对影响取能功率的因素进行了分析,...     

Analysis of power and energy loss based on long line equations

Expressions for power loss in a transmission power line are obtained based on the classical equations of a long line. It is shown that the loss and their components (in resistance and conductivity) consist of four terms depending on the square of current, the square of voltage, and the values of active and reactive power. The use of probability theory made it possible to obtain an expression to calculate the energy loss in the line characterized by a small methodological error. In addition, an approach was shown to reducing the energy loss in extrahigh voltage lines by control via reactive power flow using flexible alternative current transmission systems (FACTS).     

Features of electromagnetic processes in high-voltage power supplies with a series resonant inverter

Electromagnetic processes in high-voltage power supplies (HVPSs) based on a series resonant inverter are considered. It is shown that the analysis of a switching process in these devices should take into account the magnetizing inductance of the high-voltage transformer and capacitance of its windings. In order to decrease the dynamic losses in power semiconductor devices, the operating conditions were found and quantitative dependences between parameters of the HVPS were revealed by means of the developed HVPS mathematical model. The study results have been used in development of series of HVPSs for high-power electrophysical installations.     

高压线对机场全向信标及测距仪的电磁干扰分析

为了研究高压输电线对机场终端全向信标和DME测距仪信号的影响,选取某机场附近的高压输电线对其产生的电磁辐射进行了实际测试。通过控制和改变计算模型中参数的方法,研究了输电线路对VOR/DME信号的电磁干扰影响规律,得出飞机接收信号受高压线电磁干扰最大位置,依据电波传播的原理和国标有关规定,对在此位置的VOR/DME信号进行电磁干扰影响分析。结果表明,此处飞机能够接收到的VOR信号信噪比为42.7dB,符合国标规定的最低20dB的要求;DME信号的信噪比为97.3db,符合国家标准。在此基础上计算出高压输电线对机场VOR/DME台站的防护距离,提出了高压输电线路与机场范围VOR/DME台站的有源干扰防护距离建议。本文研究成果能够为机场附近高压输电线和机场区域通信导航监视等无线电设备的电磁兼容性设计提供依据。     

10kV长电缆空载线路合闸过程分析与应对策略

本文采用PSCAD仿真软件,对多种截面的长电缆线路空载合闸过程进行仿真分析,找出电缆线路空载合闸电流与电缆长度的关系,并仿真分析空载合闸电流的衰减过程.根据继电保护整定的基本原理,确定常用电缆线路配置电流速断保护的最大临界长度,给出长电缆线路保护配置的建议.根据10kV断路器、负荷开关等设备开断容性电流的能力,分析不同...     

Integration of a hydraulic production plant in a weak power system on a long radial line

Integrating power plants on long lines and weak power systems requires some care. To this effect, a study was conducted to determine if severe disturbances could result when a hydraulic production plant is integrated along a very long radial transmission line. Frequency responses were evaluated to identify possible resonant system operating conditions. Many events such as faults, transformer energizing and line opening were investigated. All power plant synchronous machines were represented including exciter and governor regulators. Impact of dynamic modeling of the load was examined. The study demonstrates that the overall protective strategy implemented will limit worst overvoltage constraints imposed to equipment and load within an acceptable level.     

Some thoughts on the numerical modelling of electromagnetic processes

The use of models in giving meaning to sense data is described. It is shown that models are essential to human understanding, but that there are no uniquely ‘best’ models. This leads to the discussion of the design of suitable models for engineering use. The role of physical and mathematical models is mentioned, and attention is drawn to geometrical and physical features. It is stated that numerical methods have overriding advantages, one of which is the possibility of numerical experimentation. The modelling of vector fields is discussed and attention is drawn to the ideas of differential geometry which attach the vector field to the space in which it acts. It is shown that variational methods, together with numerical experiments, can be used to derive invariant parameters which give both global and local information about electromagnetic systems in a particularly economical method of computation.     

High-frequency electromagnetic processes in electrical machines under pulse-width voltage modulation

The paper considers models and features of electromagnetic processes in systems, including electrical machines and semiconductor PWM converters. It is shown that tagging into account parameters and characteristics of high frequency electric processes is necessary in designing new electrical systems.     

Study of interconnected electromagnetic and thermohydraulic processes in the indirect inductive heating of a fluid medium

The problem of developing a mathematical model for the indirect inductive heating of liquids is considered when allowances are made for related (interconnected) electromagnetic, thermal and hydraulic processes in a system of conjugate (contacted) bodies. A model is suggested for the energy exchange process in an inductor-metal-fluid flow system with allowance for the effect of the liquid’s distribution on thermal flows and the specific power of electromagnetic sources.     

Combinations of switch states and analysis of electromagnetic processes in multilevel converters

A technique for analyzing electromagnetic processes using combinations of switch states in a multilevel converter is suggested. The influence of the imbalance of instantaneous voltages of dc section’s capacitors on the harmonic distortion of a phase current is analyzed.     

采用六相输电技术优化双回高压输电线路电磁环境的研究

随着输电线路电压等级的提升,特高压线路电磁环境问题已成为决定其杆塔尺寸的主要因素之一。文中对1 000 k V特高压双回线路和六相578 k V线路的电磁环境进行了计算和比较,结果显示采用同样的塔头和呼高情况下,六相线路的电磁环境优于三相线路。文中还研究了六相线路电磁环境随呼高的变化规律,地线及距地面最高的两根输电线的表面场强随呼高降低而降低,其余导体表面场强随呼高降低而增加;线路下方地面附近工频电场强度、无线电干扰及可听噪声均随着呼高的降低而增加。相比于同等相电压等级的三相线路,其导线表面电场强度更小。因此,六相输电可有效改善双回交流线路的电磁环境。     

Electromagnetic transients due to single pole tripping of a faulted long transmission line

This paper presents symmetrical components in the frequency domain for electromagnetic transients during single line to ground faults and single pole tripping conditions. The transmission line sections are represented by two port networks including the line frequency dependent parameters. The generators and transformers are represented by their operational impedances in the frequency domain. The boundary conditions due to single line to ground faults and/or single pole trippings are represented by superposition techniques. The final solution of the currents and voltages is then obtained using numerical Laplace transform inverse methods. The results show the overvoltage conditions on the faulted and unfaulted phases due to a single-pole tripping following a single line to ground fault. Furthermore the paper discusses details of the boundary conditions and the numerical solution.     

Relay setting considerations and operational experience of a long500 kV transmission line

The large capacitive susceptance, large load magnitude, and substantial phase unbalance before and after a single-pole trip operation have a substantial effect on the performance of the protective relaying systems of the Minneapolis-Duluth 500 kV line. Computer simulation studies show that correct operation of the relays can be assured if these effects are taken into consideration in determining relay settings. The selection, performance, and operation of the primary and secondary relay system are discussed, indicating that the relaying protection used achieved substantial security and dependability     

Analysis of electromagnetic field emitted from home plug power line used for indoor high-speed broadband communication

High-speed broadband power line communication (BPL) is a novel and practicable technique for Net-atHome or home area local area networking (LAN). Because of the characteristics of BPL, the electromagnetic wave emitted from the BPL transmission media will influence the indoor electromagnetic environment, which would also affect the performance of other wireless communications. Based on the analysis of the communication channel characteristic, network impedance and attenuation characteristic of the BPL, this paper proposes a novel model for calculating the BPL radiation and the computer simulation model, which are proved by the coherence of the simulation and the test data. The interferences from the high-speed BPL to indoor wireless communications are analyzed to stipulate the standards of high-speed BPL in the future. __________ Translated from Chinese Journal of Radio Science, 2008, 23(3): 539–544 [译自: 电波科学学报]     

Analysis of electromagnetic processes in the traction network under the interaction of electric locomotives in the regeneration and traction modes

An analysis of the results of simulation of electromagnetic processes in the “traction substation-catenary-electric locomotive” system with electric locomotives working in the feed zone in the traction and regenerative braking modes at different distances from the traction substation is carried out. A real-time computing complex was used for simulation. The mutual influence of electric locomotives and dispensing of active and reactive power was reviewed.     

A model for the quantitative electromagnetic analysis of an infinitely long solenoid with a laminated core

We present a semi‐analytical model for the quantitative investigation of the electromagnetic fields inside an infinitely long solenoid of rectangular cross section with planar laminated core comprised of interlaid dielectric and magnetic sheets. The model is based on a mathematical formulation of the electromagnetic boundary value problem inside the core as the superposition of two boundary value problems, one amenable to a closed‐form solution using separation of variables, and one amenable to a physics‐driven approximation in terms of an auxiliary problem that also lends itself to a closed‐form solution. The understanding of the underlying physics that is responsible for field penetration inside the laminate core beyond the limits imposed by the skin effect in homogeneous magnetic cores is facilitated by the solutions of these two boundary value problems. The model lends itself to the expedient quantitative assessment of the impact of laminate composition and core dimensions on the per‐unit‐length inductance and resistance of the solenoid and their variation with frequency. Copyright © 2010 John Wiley & Sons, Ltd.     

特高压交直流线路同塔架设对交流线路电磁暂态特性的影响

分别建立了±800 kV特高压直流输电线路与500 kV、220 kV交流线路同塔架设的电磁暂态仿真模型,分析了交直流线路同塔架设对500 kV、220 kV交流线路感应电压和感应电流的影响和对500 kV、220 kV交流线路潜供电流和恢复电压的影响。分析结果表明,和双回交流线路同塔架设相比,交直流线路同塔架设时,会对500 kV、220 kV交流线路产生如下影响:220 kV和500 kV交流线路中均会产生感应电压和感应电流;500 kV架设线路高抗时线路故障后潜供电流无过零点,否则潜供电流和恢复电压仅略有增加;由于220 kV交流线路通常不装设线路高抗,所以交直流线路同塔架设对其潜供电流和恢复电压影响甚微。针对500 kV架设线路高抗时潜供电流不过零的现象,提出了解决措施。     

A general procedure for investigation of electromagnetic processes of a valve engine under the full commutation

Features of physical processes in the electromechanical energy converter of a valve engine are described, and a general procedure of studying the electromagnetic processes in normal and emergency operational modes is developed that is based on them. As a result, the energy parameters and instantaneous values of output engine coordinates are obtained for these modes.