Analysis on the fault characteristics of three-phase short-circuit for half-wavelength AC transmission lines

Half-wavelength AC transmission(HWACT) is an ultra-long distance AC transmission technology, whose electrical distance is close to half-wavelength at the system power frequency. It is very important for the construction and operation of HWACT to analyze its fault features and corresponding protection technology. In this paper, the steady-state voltage and current characteristics of the bus bar and fault point and the steady-state overvoltage distribution along the line will be analyzed when a three-phase symmetrical short-circuit fault occurs on an HWACT line. On this basis, the threephase fault characteristics for longer transmission lines are also studied.

Integrated protection based on multifrequency domain information for UHV half-wavelength AC transmission line

Half-wavelength AC Transmission(HWACT)can improve capability of AC transmission significantly.According to the basic principle of HWACT,the electromagnetic transient model of HWACT is built to analyze the fault transient process of transmission line.Based on fault characteristics of HWACT,the adaptability of traditional protections for transmission lines is analyzed briefly,such as current differential protection,distance protection and over current protection.In order to solve the problems of conventional protection caused by HWACT,a novel integrated protection based on multi-frequency domain information is proposed in this paper,which uses both the power frequency information and transient information.The integrated protection based on multi-frequency domain information takes advantages of power frequency and transient protections,which can not only improve the performance of traditional protection of AC transmission line but also realize fast fault judgment by transient travelling wave protection.

Steady-state voltage-control method considering large-scale wind-power transmission using half-wavelength transmission lines

Half-wavelength transmission can transmit large-scale renewable energy over very long distances.This paper proposes an improved steady-state voltage-control method for half-wavelength transmission systems considering largescale wind-power transmission.First,the unique voltage characteristics of half-wavelength lines are deduced based on the distributed parameter model.In the secondary voltage-control level,reactive power-transmission limits of half-wavelength lines are introduced as another control objective except for tracing the pilot bus voltage reference.Considering the uncertainty and fluctuation of wind power,the overvoltage risk-assessment method of half-wavelength lines is presented to determine specific voltage-control strategies.Simulation results demonstrate that the proposed voltage-control method delivers superior tracking performance according to a voltage reference value and prevents the overvoltage risk of halfwavelength lines effectively in different wind-power penetrations.

Critical Length Criterion and the Arc Chain Model for Calculating the Arcing Time of the Secondary Arc Related to AC Transmission Lines

The prompt extinction of the secondary arc is critical to the single-phase reclosing of AC transmission lines, including half-wavelength power transmission lines. In this paper, a low- voltage physical experimental platform was established and the motion process of the secondary arc was recorded by a high-speed camera. It was found that the arcing time of the secondary arc rendered a close relationship with its arc length. Through the input and output power energy analysis of the secondary arc, a new critical length criterion for the arcing time was proposed. The arc chain model was then adopted to calculate the arcing time with both the traditional and the proposed critical length criteria, and the simulation results were compared with the experimental data. The study showed that the arcing time calculated from the new critical length criterion gave more accurate results, which can provide a reliable criterion in term of arcing time for modeling and simulation of the secondary arc related with power transmission lines.

Measurement and Simulation of Induced Voltage and Current on 110 KV Crossing Transmission Lines under UHV AC Transmission Lines

The induced electricity of 110 kV transmission lines which cross the UHV AC transmission lines may threaten personal safety of the maintenance staff. In this paper, field measurement of the induced voltage and induced current on a 110 kV crossing line inside Jinhua in Zhejiang province is performed. The electrostatic induced voltage on the measured line is 12.24 kV. The power frequency electromagnetic field simulation model is established, and the calculation results are consistent with the measured. Influence factors analysis shows that the electrostatic induced voltage on the 110 kV line is 12.78 kV, the electromagnetic induced voltage is 12.3 V, the induced current through ground wire is less than 1A when the UHV lines operate at full load. The induced voltage and current decrease while the crossing distance increases. Parallel lines induction is much higher than crossing lines. The electromagnetic induced voltage after ground knife-switch shut down would exceed the human safety voltage 36 V while the crossing angle is less than 30?, so the temporary ground wire must be hanged to ensure safety of the maintenance staff.

Radio Interference Characteristic of Ultra-high Voltage AC Transmission Lines by Using Stochastic Modeling

For developing ultra-high voltage(UHV) AC power transmission systems,it is important to precisely estimate and to limit the radio interference(RI) level of power lines.Based on the stochastic characteristics in amplitude and repetition rate of induced corona current,by using the probability theory and mathematical statistics,we establish a stochastic model for the wide-sense stationary random process of corona discharges.Then combining the stochastic model with model-propagation-analysis method,the RI levels under three-phase UHV AC transmission lines are calculated.The results of the calculation based on stochastic model method and International Council on Large Electric Systems(CIGRE) excitation function are compared with that based on semi-empirical method and some other excitation functions.The stochastic model based on different excitation functions is also adopted to simulate the RI levels under finite test lines with two opened terminations.The results indicate that with the same average maximum gradient on conductor surface and the same conductor type,the number of corona discharge per unit length is one of the main reasons that causes the difference between different excitation functions.It is also concluded that for a long test line,the effect of standing wave on RI field strength is negligible in the middle of the line,but obvious near both terminations: for a 10-km line,the maximum difference in RI field strength is 2.78 dB,between the peak value of the standing wave near the ends and the steady value near the middle of the line.

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.

基于FSC和TCSC混合复用的交直流混联线路潜供电弧特性

为提高系统运行稳定性,高补偿度串补装置广泛投入使用,但线路故障后潜供电流存在高幅值的低频分量,潜供电弧难以自熄。针对此问题,基于交直流混联输电线路,研究了不同布置方式下串补度对潜供电流与恢复电压幅值影响,提出了一种固定串补(fixed series compensation,FSC)和可控串补(thyristor controlled series compensation,TCSC)混合复用抑制潜供电弧的方法。此外,为满足线路对高补偿度的需求,设计FSC和TCSC混合复用串补度最佳配置方案。结果表明,交直流混联线路采用串补度40%的双平台分散布置方式,潜供电流与恢复电压幅值达到最小,燃弧时间最短。高补偿度串补线路TCSC采用串补度10%、20%的配置方案更利于熄弧,提高重合闸成功率。

Steady-state Voltage Reactive Compensation Method for Half-wavelength Transmission Lines Considering Equivalent Power Supply Impedance

Half-wavelength AC transmission(HWACT)refers to transmission along lines with an electrical distance of half the power frequency wavelength.The voltage amplitude at the sending terminal is equal to that at the receiving terminal in steady-state.Furthermore,the voltage at the receiving terminal does not vary with load.However,the electrical distance has been extended in actual HWACT lines because of the impact of the equivalent power supply impedance,so the attractive characteristics no longer hold.As a result,reactive power compensation methods with constant power factor and constant voltage are needed and these are presented in this paper.The steady-state operational characteristics,the calculation methods of additional reactive power compensation and the admittance of a controllable shunt reactor are also given.The methods proposed in this paper are relatively simple to implement,and the calculations involved are straightforward,resulting in effective voltage stabilization.The results indicate that such compensation methods can increase the transmission capacity while maintaining a relatively low voltage along the line.

UHVAC输电线路大跨越段的防雷保护

为确保特高压输电线路的耐雷可靠性,对晋东南-南阳-荆门UHV输电线路的黄河大跨越段和汉江大跨越段的雷电性能进行了研究并介绍了UHV输电线路大跨越段雷电性能评估的计算方法,同时根据我国输电线路大跨越段的运行情况,参考俄罗斯标准,以大跨越段在雷电过电压下的雷击无故障时间(耐雷指标)来确定防雷保护方案,还计算了UHV输电线路大跨越段的年绕击跳闸次数和年反击跳闸次数及雷击避雷线跨越档距中央的反击跳闸次数,提出了按雷电过电压要求的跨越塔塔头间隙。研究表明,我国特高压输电线路大跨越段的耐雷指标不宜<50 a。

对AC UHV输电线附近可听噪声预测公式的评估

特高压输电中,导线的选择是由输电线下的可听噪声大小决定的,所以可听噪声的预测十分重要。为了从不同机构总结出的多种半经验公式中选择最适合用来预测我国特高压交流输电线下可听噪声大小的公式,结合我国对特高压交流输电线的要求,将相导线水平和正三角排列方式下可听噪声大小的不同预测结果与测量结果进行对比和分析。结果表明:相导线水平排列大雨时可用ENEL公式或IREQ公式计算,小雨时可用ENEL或GE公式计算;相导线正三角排列大雨时可用ENEL公式或BPA公式计算,小雨时只有BPA公式最适合。所以,我国特高压交流输电线下可听噪声的计算在相导线水平排列时选用ENEL公式,相导线正三角方式排列时选用BPA公式。

交流输电线路对油气管道的干扰限值

随着能源与经济的迅速发展,交流输电线路与油气管道交叉并行的现象越来越常见,交流输电线路稳态运行与故障状态下的交流干扰对人体、管道与阴极保护设备的危害倍受广泛关注。通过对比分析国内外有关交流干扰的规范标准和最新研究成果,提出了交流输电线路稳态运行、输电线路故障时的相关干扰限值问题。建议稳态工况下人身安全电压为33 V、故障工况下采用GB/T 50065—2011《交流电气装置的接地设计规范》中的人体可以承受的接触电压计算式;管道交流腐蚀程度采用GB/T 40377—2021《金属和合金的腐蚀-交流腐蚀的测定防护准则》判定;为了避免电弧损伤,管道与接地体应有一定的安全距离;管道涂层的电气强度为25 MV/m,耐受电压值为5000 V,雷电冲击的耐压值为109 kV;恒电位仪应能承受50 Hz、30 V的持续交流干扰与1500 V的瞬间干扰,Mg阳极在交流电流密度为30 A/m^(2)时,便无法保证提供足够的阴极保护,Mg阳极不发生极性逆转的交流电流密度为100 A/m^(2)。

常规直流逆变站交流送出线路距离保护适应性分析与对策

常规直流逆变站交流送出线路故障通常会引发换相失败,存在故障电压和电流波形畸变等问题,可能导致工频相量距离保护性能劣化。首先,分析了工程中广泛应用的正序电压极化距离保护在常规直流逆变站交流送出线路中的适应性,分析结果表明,当逆变站运行于单回交流出线工况时,传统正序电压极化距离保护不再适用;然后,基于交流线路的RL模型,提出了基于波形相关系数的时域距离元件,可以不受逆变站非线性输出特性的影响,并针对时域距离元件存在的出口近区故障方向判别问题,利用电流畸变程度判断故障方向;最后,通过仿真验证了时域距离保护方案的有效性。

城市高压交流输电线路对电磁环境的影响研究

电磁环境承载无线电通信、广播和观测等业务,支撑移动互联网、物联网、卫星电视和射电望远镜等新型基础设施,保护电磁环境成为交流输变电系统设计运行的关键。该研究选取城市常见的架空220 kV交流输电线路为研究对象,测量某线路附近地面及居民楼内电场和磁场强度,分析电磁干扰的来源、产生机理、频域特征和空间衰减过程,比照城市常见无线电业务的频段和调制方式,得到典型工况下输电线路对无线电信号信噪比的影响规律,提出输电系统影响下,电磁环境保护和通信增益措施。

交流电力与信息数据双向同传的低压交流输电系统分析

随着电力电子技术与通讯技术的不断发展,采用同一电力电缆或信号电缆进行电力与信号同时传输也是构建新型电力系统的一个重要部分。本文提出了一种交流电力与信息数据双向同传的低压交流输电系统,一端负责调制数据信号作用在逆变器,另一端负责调制解调数据信号,这是一种与数据线供电和电力线载波通讯不同的信电同传方式。在分析该系统结构和工作原理的基础上,进行了仿真分析验证,结果表明该系统能够支持交流电力与信息数据的双向同传,适合较低功率低压交流功率传输的应用场合。

利用电压变化特征的识别电力系统振荡的方法

电力系统发生振荡时交流线路距离保护的测量阻抗会进入动作区,导致距离保护误动作。目前我国线路距离保护I段和II段采取了振荡闭锁措施,以防止保护误动作,但是需要人工计算静稳电流定值,整定难度大;此外,线路处于重负荷状态时,会误闭锁距离保护,闭锁期间,线路故障无法切除。该文分析了系统振荡期间保护安装处电压余弦分量(Ucosφ)特征,系统振荡期间,Ucosφ变化范围是[-1 p.u.,1 p.u.];正常运行时,|Ucosφ|变化范围是[0.707 p.u.,1 p.u.];线路发生故障后,Ucosφ固定且数值较小,根据上述特征差异,提出了利用Ucosφ识别系统振荡与线路故障的方法。该方法利用Ucosφ替代静态稳定电流,无需人工整定,自适应识别系统振荡及线路故障,在系统振荡且会导致距离保护误动时,闭锁距离保护;线路故障时,可靠不闭锁距离保护,利用实时数字仿真系统进行了仿真验证。

35 kV交流输电线路直线塔无人机巡检自动化控制系统设计

为解决35 k V交流输电线路直线塔巡检无人机自适应能力差,导致巡检作业易出错中断的问题,该文设计一种新型无人机巡检自动化控制系统。此系统由MPU9250九自由度惯性传感器、加速度计、磁力计,采集输电线路直线塔无人机巡检状态数据,通过积分法、三角函数关系、倾斜补偿方法,解算获取直线塔无人机巡检的姿态、速度、位置数据信息;使用基于模糊PID的自动化控制器,计算无人机巡检的姿态、速度、位置偏差与偏差率,自动调整无人机旋翼转速,控制无人机巡检状态,完成35 kV交流输电线路直线塔无人机巡检自动化控制。实验中,此系统使用下,无人机巡检状态与指定轨迹一致,俯仰角、横滚角、航向角偏差值为0°。

特高压交直流输电线路带电作业安全防护及碳减排效应分析

特高压(ultra high voltage,UHV)交流与直流线路同廊道运行时带电作业区域电压高、场强大,交直流混合电场比单一电场更为复杂。为确保作业人员安全,结合实际±1100 kV直流和1000 kV交流线路,建立了包含输电导线、杆塔及带电作业人员的三维计算模型,通过分析开展带电作业时人员的体表混合场强、电位转移电流及暂态能量,对作业人员安全防护进行研究。结果表明:随着作业人员不断接近直流线路,体表场强受交流线路影响越明显,最高可使作业人员体表场强增大约9%,达到1920 kV/m;交流线路的存在将导致电位转移电流增长约7%,但对暂态能量影响较小。通过对特高压线路不停电检修所减少的碳排放量进行进一步计算,验证了特高压带电作业对减少碳排放具有促进作用。

基于ANSYS Maxwell建模的超高压输电线路工频电磁场分布研究

超高压交流输电线路产生的电磁辐射可能会对生物体造成危害。为探究超高压输电线路下方电磁场环境的问题,依据有限元仿真软件ANSYSMaxwell搭建500k V单回和双回输电线路的三维模型分析主要影响因素,重点仿真研究导线在不同的距地高度、排列方式、相序分布、相间距离、相导线分裂根数及子导线半径情况下对输电线路下方工频电场和工频磁感应强度分布规律的影响,并探讨了林地和墙体对磁场的抑制作用。