Aspects of High Voltage Cable Sections in Modern Overhead Line Transmission Systems

Electrical power transmission is dominated by overhead line systems at present.This is mainly based on more than hundred years of experience of utilities in running overhead lines.Furthermore,overhead lines have proven their operational reliability and functional assurance.In the past,cables were used in distribution networks in urban areas for the most part with the exception of direct current submarine cables.New developments of high voltage XLPE cables make it possible to use this technology for EHV level applications in transmission networks.Within this paper,mixed network configurations,consisting of overhead lines and high voltage cables,are investigated.An exemplary EHV transmission line with a total length of about 100 km,which is quite typical for Central Europe,has been studied.Several different line combinations are discussed with varied rates between overhead line sections and cable sections length in practice.The length of the cable sections are ranging from several kilometers up to lengths of 100 km.In this paper the work focuses on the transient behavior of combined 400 kV overhead and cable lines during switching processes and lightning impacts.A number of calculations were carried out to get an overview of the transient stress in numerous network nodes along the transmission system.Numerical programs like ATP/EMTP have been used for these simulations.Peak values and wave shapes of the transient voltage stress have been evaluated,based on different systems and within possible combinations.In respect of the insulation coordination and transient stress at network nodes,the voltage-time trends are also analyzed.The combination of high voltage overhead and cable transmission systems,especially such with lengths of more than about 50 km,are making tightened and extended demands to the network design,to the operational management and of course to the network protection also.As an output of this investigations,the results might influence the strategy in running this new type of combined transmission systems.

CHARACTERISTICS ANALYSIS OF THE INDUCED OVERCURRENT GENERATED BY CLOSE TRIGGERED LIGHTNING ON THE OVERHEAD TRANSMISSION POWER LINE

Techniques of artificially-triggered lightning have provided a significantly useful means to directly measure various physical parameters of lightning discharge and to conduct research on protection methods of lightning electromagnetic pulses.In this study,using capacitive and resistive dividers,current probes and optical fiber transmission devices,we measured and analyzed the induced overvoltage on the overhead transmission line and the overcurrent through Surge Protective Devices(SPD) when a lightning discharge was artificially triggered nearby on August 12,2008 at Conghua Field Lightning Experiment Site.The triggered lightning discharge contained an initial current stage and eight return strokes whose peak currents ranged from 6.6kA to 26.4kA.We found that overcurrents through SPD were induced on the power line both during the initial continuous current stage and the return stroke processes.During the return strokes,the residual voltage and the current through the SPD lasted up to the ms(millisecond) range,and the overcurrents exhibited a mean waveform up to 22/69μs with a peak value of less than 2kA.Based on the observed data,simple calculations show that the corresponding single discharge energy was much greater than the values of the high voltage pulse generators commonly used in the experiments regulated for SPD.The SPD discharge current peak was not synchronous to that of the residual voltage with the former obviously lagging behind the latter.The SPD discharge current peak was well correlated with the triggered lightning current peak and the wave-front current gradient.The long duration of the SPD current is one of the major reasons why the SPD was damaged even with a big nominal discharge current.

New Monitoring Technologies for Overhead Contact Line at 400 km.h-1

Various technologies have recently been developed for high-speed railways, in order to boost commercial speeds from 300 km.h： to 400 km.h-1. Among these technologies, this paper introduces the 400 km-h-1 class current collection performance evaluation methods that have been developed and demonstrated by Korea. Specifically, this paper reports details of the video-based monitoring techniques that have been adopted to inspect the stability of overhead contact line （OCL） components at 400 km.h-1 without direct contact with any components of the power supply system. Unlike conventional OCL monitoring systems, which detect contact wire positions using either laser sensors or line cameras, the developed system measures parameters in the active state by video data. According to experimental results that were obtained at a field-test site established at a commercial line, it is claimed that the proposed mea- surement system is capable of effectively measuring OCL parameters.

Software Tool for the Implementation of the Methodology for Revitalization of High-Voltage Overhead Power Lines

In power systems, a large number of OPLs （overhead power lines） are more than 40 years old and some even exceed 50 years old. The key issue for power systems managers, public utilities companies and electrical engineers today concerns the manner in which available financial resources should be invested in these OPLs to provide the greatest impact on the power system as a whole and to address the OPLs that require urgent revitalization. This paper presents the application of the software tool RevOPL, developed using Microsoft Access utilizing the ＂methodology for revitalization of high-voltage OPLs＂. The aim is to present both the methodology and software to objectively evaluate the condition of an OPL and determine its remaining service life. The application of this software tool provides a proposal for the scheduling and scope of planned revitalization activities, which are obtained through the optimization of the technical characteristics while remaining within the available budget.

The Study of Overhead Line Fault Probability Model Based on Fuzzy Theory

In the background of the design and construction of Smart Grid Operation Supporting System for District Power Networks, this paper established the weighted fault probability model of the overhead line which is based on equipment operating status, utility theory and fuzzy theory. In this model, the proper membership function is adopted to describe the influence of lightning, wind speed, line ice and temperature, and the outage rate of overhead line, derived from historical statistics, is amended. Based on this model, the power supply risk analysis software is developed to calculate the online risk indicators of district grid, and provide real-time decision support information based on risk theory for scheduling operations personnel.

Simulations of the Allowable Load Current of the Overhead Lines in the Latvian Power Network

This paper considers the influence of changes of the transmission lines of permissible load current depending on conductor and ambient temperatures, climate conditions. The theoretical background of the allowable conductor temperature as well as load current determination principles are proposed. On one hand, the principles are based on mechanical limitations; on the other hand, they are based on thermal limitations. The simulation tasks were based on specific data information of three existing overhead lines of Latvian power system as well as the planned 330 kV overhead line. Moreover, the special thermovision device was used for precious determination of conductor temperature of the existing transmission lines. The simulation results of the obtained data are reviewed in the paper.

Design of 1000-kV AC Single-Circuit Overhead Transmission Line

The UHVAC 1 000-kV transmission system is so far the one with the most advanced transmission technique applied and highest operation voltage.There are no guidelines or standards available for the design of 1 000-kV overhead transmission line in China.Study on key technologies and design schemes shall be carried out to ascertain the technical principles and construction standards for project construction,which are presented in this paper based on the Southeast Shanxi-Nanyang-Jingmen test and demonstration transmission line.A comparison and analysis of technical data and economic indices between UHV line and other lines are also described.

Determining of the Real Condition of High-Voltage Overhead Power Lines

Significant investments have been made regarding the construction of a great number of high-voltage overhead power lines of all voltage levels, and now the questions arise on where and how to direct the investments necessary for the maintenance of overhead power lines. To organise the process of maintenance of overhead power lines correctly, it is necessary to have the current information on the condition of particular components of a line. In this paper, special attention has been paid to the real condition of overhead power lines, with the aim of making the decision whether some of the following measures are necessary, and to what extent： the revitalisation for a certain number of years is perceived, the revitalisation up to five years and reconstruction of the overhead power line is performed, its restoration is performed or nothing is done. The approach to the perceiving of real condition of high-voltage overhead power lines is presented on a global block diagram. With the aim of setting out the list of priorities for revitalisation, the criteria have been defined with regards to the real condition of particular components of an overhead power line, as well as pursuant to the role and importance in an electric power system. The correctly defined criteria contribute to the solving of the problem of making a single list of priorities for the revitalisation of high-voltage overhead power lines. In that way, the recommendations are being given to the transmission companies, to achieve a higher reliability of an electric power system, with a minimum number of cancellations and a maximum extension of working life of all the components of overhead power lines. A correct maintenance of overhead power lines brings large financial savings to the owners of transmission companies, and that is the primary goal in a deregulated environment.

Hand-eye-vision based control for an inspection robot's autonomous line grasping

In order to ensure that the off-line arm of a two-arm-wheel combined inspection robot can reliably grasp the line in case of autonomous obstacle crossing,a control method is proposed for line grasping based on hand-eye visual servo.On the basis of the transmission line's geometrical characteristics and the camera's imaging principle,a line recognition and extraction method based on structure constraint is designed.The line's intercept and inclination are defined in an imaging space to represent the robot's change of pose and a law governing the pose decoupling servo control is developed.Under the integrated consideration of the influence of light intensity and background change,noise(from the camera itself and electromagnetic field)as well as the robot's kinetic inertia on the robot's imaging quality in the course of motion and the grasping control precision,a servo controller for grasping the line of the robot's off-line arm is designed with the method of fuzzy control.An experiment is conducted on a 1:1 simulation line using an inspection robot and the robot is put into on-line operation on a real overhead transmission line,where the robot can grasp the line within 18 s in the case of autonomous obstacle-crossing.The robot's autonomous line-grasping function is realized without manual intervention and the robot can grasp the line in a precise,reliable and efficient manner,thus the need of actual operation can be satisfied.

Algorithm Study and Software Design of District Grid On-Line Risk Assessment Based on Fuzzy Theory

In the background of the design and construction of Smart Grid Operation Supporting System for District Power Networks, this paper established the weighted fault probability model of the overhead line which is based on equipment operating status, utility theory and fuzzy theory. In this model, the proper membership function is adopted to describe the influence of lightning, wind speed, line ice and temperature, and the outage rate of overhead line, derived from historical statistics, is amended. Based on this model, the power supply risk analysis software is developed to calculate the online risk indicators of district grid, and provide real-time decision support information based on risk theory for scheduling operations personnel.

10kV架空线路间隔棒安装机器人上下线辅助系统研究

针对已研发的10 kV架空线路相间间隔棒安装机器人需要在地面完成上线和下线的问题,综合考虑上线和下线过程中机器人的安全防坠落、吊装时吊环的防滑以及高空远距离完成摘钩和挂钩等操作,研究了适合远距离摘挂的吊环,选用了不同的上下线吊钩以及同步上线或下线的电动绞盘系统,上下线辅助系统由举升杆、新型吊环、上下线吊钩、电动绞盘等组成。通过模拟试验验证了方案的可行性,试验结果表明:本辅助系统可帮助工作人员在地面完成对10 kV架空线路相间复合间隔棒安装机器人的上下线操作。

城市轨道交通9号道岔上方接触网结构设计与调整

道岔上方的接触网结构较复杂,是维修维护需要重点关注的区域。本文针对某地铁线路9号道岔上方接触网出现的受电弓弓角异常磨损、接触线侧面异常磨损等问题,从受电弓、接触网空间几何关系出发,分析了造成线岔区域异常磨损的原因,给出了线岔布置的原则和线岔结构的调整方案建议,为城市轨道交通9号道岔上方接触网布置提供参考。

大风区接触网线路参数对附加导线舞动的影响

针对大风环境下兰新高速铁路接触网附加导线发生剧烈舞动以及线间放电的现象,依据接触网附加导线结构特点,建立了附加导线有限元计算模型,并对附加导线进行找形计算。采用谐波叠加法模拟接触网附加导线处的随机风场,并对导线模型施加风荷载,利用无条件稳定Newmark法以及荷载增量法,分析接触网线路参数对附加导线舞动及线间距离的影响规律,并给出相应的舞动防治措施。结果表明:40 m及更小档距对导线在低风速及高风速下的舞动均有明显的抑制效果;将附加导线运行张力提高至6.5 kN,导线阻尼比提高至1.5%及以上能有效降低两条导线的舞动剧烈程度;接触网附加导线的档距过大,运行张力及阻尼比过小,将导致导线舞动时悬挂点张力过大,易引起导线掉线、断线等事故;随附加导线档距减小、运行张力及阻尼比增大,线间最小距离呈递增趋势;不同线路参数下(档距、运行张力及阻尼比)附加导线舞动时线间最小距离均随风速增大出现减小趋势。本研究可为兰新高铁大风区段接触网附加导线舞动及线间放电的防治提供有效的理论依据。

高压杆塔设备无线供电技术剖析

高压杆塔设备的种类和数量随着智能电网和5G新基建的蓬勃发展而日益增多,现有的蓄电池供电方式可靠性较差且所需运维工作量大,供电成为它们必须面对的重要问题。近年来,通过架空输电线路取电,再将电能无线传输给电力杆塔设备的供电技术,已经显示出具有良好的发展和应用前景。为此,该文从供电系统组成、取电装置、磁耦合机构、补偿网络、电能变换器及控制方法几个方面,对电力杆塔设备无线供电技术现有发展状况进行系统的分析,指出应用前景以及系统亟待解决的问题,并探讨无线供电技术在传输效率、抗偏移、鲁棒性以及产品化等方面的发展趋势。

融冰隔离开关防误操作方式探究

通过对一起带负荷操作线路融冰隔离开关分闸的事件的分析,并对事件发生前调度下令流程及融冰作业流程进行梳理,总结了此次事件成因。认为由于高原气候影响,致使融冰操作过于频繁,作业量的突增也加大了人为误操作的可能,针对此情况并结合现阶段电气化铁路接触网所使用的融冰方式,对后期融冰操作流程提出了相应改进意见。

架空线路综合在线监测系统设计与安装研究

架空线路综合在线监测系统注重与环境保护部门的合作,共同推动电力行业的绿色发展。因此,本文介绍了该系统与其他技术的融合与应用的重要性,如物联网、大数据和人工智能等,以提高系统的性能和效率。通过不断优化设计方案和提升系统性能,架空线路在线监测系统将为电力系统的安全稳定运行提供有力支撑,同时为构建绿色、低碳的能源体系发挥重要作用。

高压架空输电线路与变电站监测研究

随着科学技术的发展,各种先进的技术被广泛应用于电力领域,其中视频监控系统就是典型代表,电力企业可以将其应用于高压架空输电线路监测,用于掌握线路的情况,以消除其他因素对线路造成的不利影响。并且,在智能变电站快速发展时期,还应设计在线监测系统,实时掌握变电站动态,以保护变电站始终处在平稳运行状态。文章就高压架空输电线路和变电站监测展开研究,通过结合实例的方式,提出系统设计和布置的要点,以望借鉴。

电气化铁路接触网供电线T接方式优化方案研究

从电气化铁路接触网供电线长期运行情况来看,供电线采用T接方式上网可靠性低,是影响供电线安全的薄弱环节。就某次供电线上网点T接引线断脱造成的事故,分析既有供电线T接方式薄弱点,提出2种优化供电线T接方式设计方案。通过对比得出,供电线采用整锚段直接上网方案与实际维护检修能力相匹配。采用整锚段直接上网方式对供电线改造,经过1年多不间断地监测、检查表明,供电线故障率明显降低,运行温度进一步下降,维护检修更加便利。

160 km/h市域快线架空刚性接触网系统设计方案研究

架空刚性接触网作为传输列车牵引电能的载体及受电弓滑动取电的机械滑道,是市域快线供电系统的重要组成部分。为保证其能够持续、稳定、可靠地向列车传输电能,文章以国内第一条采用架空刚性接触网授流、速度高达160 km/h的全地下市域快线——广州地铁18号线为例,在分析其架空刚性接触网设计要求的基础上,采用理论计算、有限元仿真等技术手段对架空刚性接触网设计方案进行全方位研究,确定悬挂方式、导高、标准跨距、锚段长度、拉出值布置方案,以及分段绝缘器、膨胀元件及弹性线夹等关键设备的选型要求,并通过仿真及工程实例验证设计方案的有效性,以期为类似工程提供参考和借鉴。