Basic electrical processes in dielectric liquids

The basic processes of electrical conduction in dielectric liquids are reviewed, attention being drawn to the similarities between conductive electrolytes and insulating liquids. The concepts of the electronic amorphous solid state are employed to provide a framework for the review. The conditions at metal electrodes can be incorporated naturally into the scheme, and it is known that the space charge layers occurring on them can control conduction. Although electrical breakdown itself is not considered, the underlying electronic processes which will develop when breakdown electrical fields exist in the liquid are considered     

Electrical Insulating Papers?an Overview

Electrical grade natural fibers continue to play an important role as components in dielectric systems.     

Instantaneous active and reactive powers in electrical network theory: A review of some properties

Research into electric power has been on-going since the end of the 19th century. The concepts of instantaneous active and reactive power are the result of the work carried out in the last few decades. In particular, they are used in the optimization of power systems, but they also form part of the general theory of electrical networks.Nevertheless, instantaneous active and reactive powers show noteworthy differences with other electrical powers. Here we review some of their properties and attempt to draw some conclusions that should be taken into account for their correct use. In particular we show the ambiguity of expressions such as “the branches of a network” or “the branches of a multi-terminal network” when these powers are involved.     

基于CatBoost的常用电器负载电弧故障识别方法

电气火灾造成的危害日益受到人们重视,其成因中占比最大的是电弧故障。电弧通常是由电气组件的损坏或过载而导致,进而可能会导致电气设备的损坏并引发火灾。电弧识别是一种重要的电弧故障预防性技术,可以监测电气设备中的电弧事故,以便及时采取应对措施,是智能用电的重要组成部分。文中就电弧故障识别方法展开研究,首先按照国标搭建了实验平台,然后分析不同家用电器负载组合的电弧特征,并进行特征提取;接着提出了一种基于CatBoost分类模型的电弧识别方法,使用CatBoost模型对提取到的特征进行训练,以实现电弧故障的快速识别;经过测试集验证,与现有的SVM、Random Forest等常用识别分类方法相比,提出的基于CatBoost分类模型的电弧识别方法具有更高的准确率和召回率,能够有效提高电弧事故的识别精度。     

Hydrodynamic model for electrical arc modelling [in circuitbreakers]

A hydrodynamic model for electrical arc modelling is presented. The model, which takes into account Joule heating, radiation, Laplace forces, arc-wall interactions and real gas effect, has been validated through comparisons with measurements. Industrial applications have already been computed and concern high, medium and low voltage circuit breakers     

正极材料高温热处理后锂硫电池电气性能变化

采用多壁碳纳米管(MWCNT)、气相生长碳纤维(VGCF)、活性炭(AC)为单质硫的载体,通过高温热处理的方法制备锂硫电池用S/C正极材料。通过对所得材料进行X射线衍射光谱法(XRD)、扫描电子显微镜法(SEM)、热重分析、恒流充放电及循环伏安测试等对材料的结构及电气性能进行分析。研究发现,锂硫电池的放电比容量及循环性能受碳材料的影响较大,其中S/VGCF复合材料的电化学性能较好,当以0.1 C的电流在1.5~3.0 V进行充放电时,其首次和第100次循环的放电比容量分别为1 205.62、613.18 m Ah/g。     

On the symmetry features of some electrical circuits

The use of symmetry of some nonlinear circuits, composed of similar resistive (more generally, algebraic) elements, is considered for the analysis of the input resistive function of such a circuit. The focus is on recursively obtained (‘fractal’‐type) 1‐ports, analysed using the concept of α‐circuit introduced by Gluskin. The methods under study should be of interest for the analysis and calculation of complicated nonlinear resistive (algebraic) 1‐port structures, e.g. grid cuts for different symmetry conditions. Copyright © 2006 John Wiley & Sons, Ltd.     

Electrical Insulating Liquids for Power Cables?an Overview

Today synthetic liquids are more widely used than conventional mineral oils, due to their superior electrical performance and greater availability.     

The effect of electrode-holding arms on the electrical parameters of the bus-tube section of current lead in an arc steel furnace

The essence of the electromagnetic effect of metalware located near current-carrying elements has been shown. Aftereffects, such as heating of metalware, additional active losses of power supply, perturbation in the magnetic field, and consequent changes in the active resistance and inductive reactance of the equivalent circuit of a furnace have also been considered. The existing technique of taking into account the influence of metalware located near current-carrying elements on the electrical parameters of the current lead of high-power technological equipment has been examined, with its drawbacks being revealed. A method for increasing the accuracy and range of applicability of the technique has been suggested. To do this, a more universal coefficient of neighboring metalware (CNM) has been introduced. The coefficient allows us to take into account the influence of metallic structures on the resistance and magnetic reactance of the furnace circuit. The results of numerical simulations for a bus-tube section of current lead in a 100-t arc steel furnace (ASF) have been presented. The results of simulations were compared with the experimental data obtained by physical modeling of current lead of a 100-t ASF. A numerical model validated by such a way was used to obtain the dependences of active resistance and inductive reactance and CNM on the geometry of the investigated section and the properties of electrode-holding arms. The obtained dependences are the basis for an engineering technique intended to design current leads for an arc steel furnace.     

Determination of the streamers characteristics propagating in liquids using the electrical network computation

This work is devoted to the modeling of branching streamers propagating in transformer oil using an equivalent electrical network and the electrical network computation. The proposed model enables one to determine the different characteristics of the streamer (i.e., the associated current and the electrical charge, the power and the energy injected in the liquid, the local electric field at the streamer head, the streamer shape and its velocity, the mobility of the charge carriers within the streamer channels, the local viscosity and temperature). It's shown through the simulated values of the mobility of charge carriers, the local viscosity and temperature that both electronic and gaseous mechanisms are implicated in the streamer development. The gaseous nature of streamers and the role of the local electric field are evident. The influence of the conductivity and additives as well as the electrode gap on the propagation velocity of positive streamers is analyzed.     

Latest technical trend of arc plasma,electrical contacts,and their applications

Arc plasma generated by arc discharges is used in various fields because of its extraordinary characteristics such as very high temperature and high energy density. On the other hand, the principle of current interruption by extinguishing the arc discharge between electrical contacts is practical and useful in many types of circuit breakers. Arc discharge and electrical contacts have been well investigated, and numerous procedures have been developed. In this review paper, we introduce the recent technical trends in arc plasma treating wastes, synthesizing new materials, and the latest circuit breakers equipped with arc plasma and electrical contact techniques. Copyright © 2007 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

On some optimal control problems for electrical circuits

Some optimal control problems for linear and nonlinear ordinary differential equations related to the optimal switching between different magnetic fields are considered. The main aim is to move an electrical initial current by a controllable voltage in shortest time to a desired terminal current and to hold it afterwards. Necessary optimality conditions are derived by Pontryagin's principle and a formal Lagrange technique. In the case of a linear system, the principal structure of time‐optimal controls is discussed. The associated optimality systems are solved by a one‐shot strategy using a multigrid software package. Various numerical examples are discussed. Copyright © 2013 John Wiley & Sons, Ltd.     

Dielectric Recovery of an Airblast Monoflow Model Interrupter with Insulating Nozzle

The effect of the upstream gas flow field and the electric field distribution on the dielectric recovery characteristic were studied using a GBI, with an insulating nozzle, operating in air. Four distinct stages of recovery were identified and changes in upstream pressure primarily influenced the first stage recovery. Also, increasing the upstream radial gas velocity improved the recovery speed during the early stages, but increasing the axial component resulted in an overall higher final dielectric strength.     

一起合成绝缘线路避雷器断裂事故原因分析

分析了500kV江茂线线路避雷器断裂事故原因,指出避雷器间电气连接不良是导致避雷器断裂的主要原因。     

Calculation of an interruption arc current and time of arc quenching in low-voltage current breakers

For the analytical calculation of an arc current in the process of arc quenching, an average statistical curve of a change of an interruption arc voltage is constructed and mathematically described. This curve is based on experimental data obtained during short-circuit current interruption by nonspeed and selective circuit breakers of different design, in particular, with different volumes of arc chutes. Features of short-circuit current interruption in a three-phase system are considered.     

Fabrication and electrical properties of PC-PNZT-PVDF-GO composites

The objectives of this research are to fabricate and investigate new smart composites for the sensing and actuation applications in civil engineering. The fabrication and properties of cement-based piezoelectric ceramic composites are emphasized. However, cement-based piezoelectric composites are still difficult to obtain great electrical properties due to the evidence of some pores in the composites. Therefore, a novel approach to effectively improve their polarization of piezoelectric ceramic is to add a semiconductor (graphene oxide) and an insulator (polyvinylidene fluoride) phases between piezoelectric particles by the introduction of a small volume fraction of a third phase. Microstructure of the new composites was investigated using Scanning electron microscope (SEM). Dielectric permittivity and ferroelectric properties were then investigated.     

磁性离子液体的物性及其影响因素

磁性离子液体作为一种具有磁性的功能化离子液体,近年来受到广泛关注。讨论了常见磁性离子液体的合成与表征方法,对影响磁性离子液体物性参数(如密度、粘度、磁化率、热性能、离子电导率)的有关因素进行了分析,为进一步深入研究磁性离子液体提供参考。