Nonlinear dynamical response of high-voltage transmission lines based on cable dropping

In order to study the dynamic response of high-voltage transmission lines under mechanical failure, a finite element model of a domestic 500-kV high-voltage transmission line system is established. The initial equilibrium condition of the coupling system model is verified by nonlinear static analysis. The transient dynamic analysis method is proposed to analyze the variation law of dynamic response under cable or insulator rupture, and the dynamic response of structural elements next to the broken span is calculated. The results show that upper crossarm cable rupture has no effect on cable tension at adjacent suspension points, but it has a significant influence on tension in the insulator and the tower component of the upper crossarm next to the broken span. The peak tension in the conductor of the upper crossarm at the suspension point exceeds the design value under insulator rupture. Insulator rupture has no effect on the tower component of the upper crossarm, but it has a significant influence on insulator tension of the upper crossarm. Insulator rupture should be taken into account in the design of overhead transmission lines. The research results can provide a theoretical basis for the design of transmission lines.

Mechanical analysis of transmission lines based on linear sliding cable element

In order to study the sliding characteristics when the cable structures are connected with other rods, a string of sliding cable dements （SCE） consisting of one active threenode SCE passing through the sliding point and multiple inactive two-node SCEs is put forward. Based on the updated Lagrangian formulation, the geometric nonlinear stiffness matrix of the three-node straight sliding cable dement is deduced. The examples about two-span and three-span continuous cable structures are studied to verify the effectiveness of the derived SCE. Comparing the cable tension of SCE with the existing research results, the calculating results show that the error is less than 1%. The sliding characteristics should be considered in practical engineering because of the obvious difference between the cable tension of the SCE and that of the cable element without considering sliding characteristics.

Mechanical response of transmission lines based on sliding cable element

In order to study the sliding characteristics when the cable is connected with the other rods in the transmission line structures,a linear sliding cable element based on updated Lagrangian formulation and a sliding catenary element considering the out-of-plane stiffness coefficient are put forward.A two-span and a three-span cable structures are taken as examples to verify the sliding cable elements.By comparing the tensions of the two proposed cable elements with the existing research results,the error is less than 1%,which proves the correctness of the proposed elements.The sliding characteristics should be considered in the practical engineering because of the significant difference between the tensions of sliding cable elements and those of cable element without considering sliding.The out-of-plane stiffness coefficient and friction characteristics do not obviously affect the cable tensions.

A Review of Medium Voltage Single-Core Cable Armouring, Induced Currents and Losses

Insulated underground cables have the potential to reduce power outages, maintenance costs, and transmission losses compared to overhead lines. On the other hand, they are exposed to several risks and physical damages, since they are buried in the ground. Though the cables are armoured in order to provide mechanical protection and achieve tensile strength, and also to provide effective conductance of earth fault currents. The main purpose of this paper is to introduce insulated underground cables, armouring process, and to analyze the induced currents in metallic parts such as sheath and armour that causeohmic losses which are categorized mainly in two groups as circulating current and eddy current. This paper presents a review on analytical techniques used to analyze the effect of magnetic fields, andcalculate the losses in the armour of the cables, besides providing the strategies and solutions used for armour loss reduction.

Analysis of DC Power Transmission Using High T_c Superconducting Cables

A conceptual superconducting DC cable model is designed and its magnetic fields distribution is analyzed with Ansoft/Maxwell soft. A DC Power transmission system is also studied by using the Matlab/Simulink. With the DC Line and AC Ground Fault, the system losses analysis is introduced.The analysis results mainly include the magnetic fields distribution of the HTS cable model with Ansoft/Maxwell, the system loss, the DC Line and AC Ground Fault with Matlab/Simulation.

Development and prospect of downhole monitoring and data transmission technology for separated zone water injection

This article outlines the development of downhole monitoring and data transmission technology for separated zone water injection in China.According to the development stages,the principles,operation processes,adaptability and application status of traditional downhole data acquisition method,cable communications and testing technology,cable-controlled downhole parameter real-time monitoring communication method and downhole wireless communication technology are introduced in detail.Problems and challenges of existing technologies in downhole monitoring and data transmission technology are pointed out.According to the production requirement,the future development direction of the downhole monitoring and data transmission technology for separated zone water injection is proposed.For the large number of wells adopting cable measuring and adjustment technology,the key is to realize the digitalization of downhole plug.For the key monitoring wells,cable-controlled communication technology needs to be improved,and downhole monitoring and data transmission technology based on composite coiled tubing needs to be developed to make the operation more convenient and reliable.For large-scale application in oil fields,downhole wireless communication technology should be developed to realize automation of measurement and adjustment.In line with ground mobile communication network,a digital communication network covering the control center,water distribution station and oil reservoir should be built quickly to provide technical support for the digitization of reservoir development.

基于S-CDMA技术CableModem的应用

在进行 Ｉｎｔｅｒｎｅｔ 接入方式对比的基础上，介绍了 Ｈ Ｆ Ｃ 结构 Ｃ Ａ Ｔ Ｖ 网对高速数据传输的适应性，并结合 Ｈ Ｆ Ｃ 网和 Ｓ－ Ｃ Ｄ Ｍ Ａ 技术的特点，提出了基于 Ｓ－ Ｃ Ｄ Ｍ Ａ 技术 Ｃａｂｌｅ Ｍｏｄｅｍ 应用的可行性。

Cable Modem的原理与反向噪声的控制

介绍CableModem的基本概念、传输方式、标准规范 ,并对影响CableModem工作稳定性的反向噪声问题进行技术分析 。

Analysis of the Quasi-Static Buffeting Responses of Transmission Lines to Moving Downburst

Downburst event is identified as a major cause to failure of transmission lines in non-coastal regions.In this paper,a novel nonlinear analytical frame for quasi-static buffeting responses of hinged and multi-span insulator-line systems are derived based on the theory of cable structure.The closed-form solutions are presented and applied to predict nonlinear response including displacements and other reactions of the system subjected to a moving downburst wind in a case study.Accuracy and efficiency of the derived analytical frame are validated via comparisons with results from finite element method.

VIDEO TRANSMISSION SYSTEM IN ITV APPLICATION

The transmission characteristics of video transmission mediums,coaxial ca ble and optical fiber,are discussed in the paper. The formulas for frequency bandwidth are given to evaluate the video transmission distance. For typical video transmission systems with BB/IM and PFM/IM tising optical fiber as the channel, expressions and calculating results for both S/N and sensitivity are given. Finally, the principle for se lecting different type of transmission systems according to transmission distances of the industrial TV is presented.

Transmission Line Modelling of Geomagnetic Induction in the Ocean/Earth Conductivity Structure

During geomagnetic disturbances, electric fields induced in the Earth and in power systems, pipelines and submarine cables can interfere with the operation of these systems. Calculations for submarine cables are complicated by the need to consider not just the induction directly into the cable but also the earth potentials produced at the coast at each end of the cable. To determine the coast potentials, we present a new model of the ocean and earth conductivity structure that spans the whole length of a cable from one coast to another. Calculations are based on the generalised thin sheet approach introduced by Ranganayaki and Madden but converted to a transmission line model that can be solved using standard circuit theory techniques. It is shown how the transmission line model can be used to calculate the earth potential profile from one side of an ocean or sea to the other. Example calculations are presented for a shallow sea, a shallow ocean, and a deep ocean that are simplified approximations to the North Sea, Tasman Sea and Pacific Ocean and show that the peak potentials occur at the coast. An examination is also made of how the width of a shallow sea and the width of the continental shelf affect these coast potentials. The modelling technique and example results provide a guide for more detailed modelling of geomagnetic induction along the routes of specific submarine cables.

Live-Grid Operation and Maintenance of the 35 kV/121 MVA Superconducting Cable System

A 33.5 m, 35 kV/121 MVA, three-phase, warm dielectric HTS power cable system was successfully installed and activated in China Southern Power Grid at the Puji substation in Kunming on April 19th of 2004, supplying electricity to four industrial customers （including two metallurgical refineries） and a residential population of about 100000. In this paper, we give an update on the operation and maintenance status of the system and comments on reliability issues. We conclude that the superconducting cable system is currently quite robust and feasible for particular utility applications, and it will be improved by advancement in cryogenic equipment and system technology.

A real time transmission system of long distance for nuclear logging

Some specified chips in traditional Manchester-Ⅱencoding/decoding designs are used to guarantee strictly the stability of the input wave,otherwise the capacity of anti-interference and resilience are degraded seriously.In this paper,a new Manchester-Ⅱencoding/ decoding system is used for nuclear logging by a 7 000 m armoring cable.A thorough hardware wave tracking decoding algorithm is proposed and realized in a FPGA hardware chip.An on-site measurements show that this transmission system can decode correctly in real time,with a bit error rate of better than 10^(-10).

Theoretical Analysis of Measurement in Operation Efficiency in Optical Cable Transmission Networks

It is necessary to study dynamic operation efficiency of transmission networks in order to realize high intensification of communication networks. The operation efficiency discussed here should exist not only in logic-circuit layer, but also in both path layer and medium layer. A theoretical method of the measurement of layers and comprehensive evaluations is presented based on the concept of transmission efficiency.

基于LSTM的高压输电电缆接头异常预警系统设计

高压输电电缆接头异常预警容易受到谐波电流影响,导致预警效果不佳,为此设计了基于LSTM的高压输电电缆接头异常预警系统。检测高压输电电缆接头异常电流谐波,获取电缆接头介质状态。设计CC2430微处理器预警模块,负责处理预警区域内电流数据。构建接地线电流检测模块,负责评估电缆接头异常。构建LSTM神经网络预警模型,对比分析实时状态与模型中检测点状态,获取当前电缆接头状态的预测值。采用移动平均技术分析电流数据的整体变化走向,判断电流预测数据与阈值关系,根据系统指示灯颜色区分异常等级。由实验结果可知,该系统电流数值最大值为125 A,变化曲线与实际曲线一致,说明该系统的预警效果较好。

虚实结合的传输线工作状态仿真与应用实验设计

针对传统微波实验少、教学难和设备维护成本较大、实验与工程脱节等问题,以同轴电缆故障检测为应用背景,将传输线理论与工程应用结合,设计虚实结合的传输线工作状态仿真与应用实验。采取工程问题引入、虚实结合、软硬搭配的方式,从传输线工作状态分析入手,利用终端短路和开路传输线模拟存在短路或断路故障的同轴电缆,通过仿真完成故障建模分析,掌握不同工作状态下电压、电流、阻抗和反射系数特性,自主设计方案完成故障检测。实践结果表明,传输线工作状态仿真与应用实验有利于学生深化对理论的理解、明晰理论的应用和提升解决工程问题能力,较好地满足实验教学要求。

基于架空光缆的高稳定频率信号传递技术研究

为解决架空光缆因晃动幅度大和温度变化剧烈引起的相位噪声恶化问题,采用双向传输与预补偿技术,设计了基于电子相位补偿的光纤频率传递方案,在包含30 km架空光缆、总长133 km的实际链路上进行频率传递试验,与单向传输设备相比相位噪声指标提高28 dB;采用双向传输光纤频率传递技术,在包含架空光缆与133 km全部埋地光缆进行对照测试,在5级风力情况下架空光缆传递相较恶化了4 dB,均可以满足架空光缆下频率传递使用需求;经实地试验表明,基于电子相位共轭的光纤频率传递技术可以优化经架空光缆传递后频率信号的相位噪声,为分布式雷达、分布式守时系统及航天测控等系统多站间同步方案提供支撑。

公铁合建斜拉桥钢桁-混凝土板组合梁受力特性

以某主跨808 m的公铁合建新型钢桁-混凝土板组合梁斜拉桥为背景,采用ANSYS软件建立局部组合梁细化的全桥多尺度有限元模型,分析其在不同工况下双层组合梁的受力传力特性和混凝土桥面板荷载分配比,并讨论混凝土桥面板厚度t_(b)、横梁刚度变化系数λ_(K)和钢与混凝土弹性模量比λ_(E)对组合梁受力传力的影响规律。结果表明:最不利组合工况下,钢桁架最不利Von Mises应力为183.6 MPa,混凝土桥面板最大拉应力为5.3 MPa,均满足结构受力要求;沿纵向路径,钢桁架和混凝土桥面应力在节间横梁间均呈“波形”分布;上下层混凝土桥面板顶、底面应力沿横向近似呈“W”和“M”状分布,表明桥面板承受一定沿横向不均匀分布弯矩;公路及铁路混凝土桥面最大剪力滞系数分别为1.45、1.36,更宽的公路混凝土桥面剪力滞效应更显著;公路及铁路混凝土桥面分别承担上、下层结构57.46%~79.99%和33.21%~62.81%的轴向荷载,为组合梁的主要传力构件;混凝土桥面板的应力随t_(b)及λ_(K)的增大而增大,随λ_(E)的增大而逐渐减小;混凝土桥面每层平均荷载分配比ξ与t_(b)成正比,与λ_(K)及λ_(E)成反比;当t_(b)、λ_(K)和λ_(E)参数的取值范围分别为0.8~1.4、0.4~1.6以及4~10时,组合梁混凝土桥面应力及荷载分配比ξ较为合理。

88.9mm套管电缆传输燃气动力补贴技术研究及应用

在油田开发的中后期油气田增产作业过程中,由于地质因素等造成油气井套管损坏,套管损坏制约着油气井正常生产,甚至可能导致井筒溢流等严重后果,及时有效地封堵加固受损套管,是保证油气井正常生产的重要技术手段。研究并设计了88.9 mm(3.5″)套管电缆传输燃气动力补贴工具。介绍了燃气动力补贴工具的原理和技术特点,借助有限元模拟对膨胀锥和锚定结构及工具参数进行了优化设计,并完成了地面试验和该技术及工艺的现场应用,补贴后全井筒试压50 MPa,稳压10min,压降0.7 MPa。现场应用表明:该工具设计合理,首次使用电缆传输便取得了成功。

滤波电缆原理与应用展望

电缆被称为工业的“血管”和“神经”,广泛应用于设备互联。然而,传统电缆不具备分布式滤波功能,通常成为电磁兼容(EMC)性问题的主要耦合路径。滤波电缆,可以通过在绝缘电线上包裹采用柔性印刷电路板(FPCB)制造的特定缺陷导体层(DCL)、在绝缘圆柱体上包裹缺陷导体传输结构(DCTS),使其能够在轴向上实现分布式滤波功能。DCL或DCTS上具有特定蚀刻图案的导体起到等效的集总电路作用,被加到电缆电路中实现滤波功能,从而抑制干扰信号。采用微波网络分析技术可以高效地分析级联特性。国内外的研究现状和本团队的主要研究成果表明,滤波电缆能够有效实现分布式滤波功能,有望为复杂电磁环境防护提供一种新的解决方案。