OPTIMIZATION OF TRANSIENT FEEDING TO PARALLEL-PLATE TRANSMISSION LINES FROM COAXIAL LINE

The transient feeding to parallel-plate transmission lines from coaxial line is optimized by using the Finite-Difference Time-Domain (FDTD) method and a simple FDTD feed model. Observing the reflected voltages, this letter presents the optimal feeding position and ratio of width to height for a given input impedance of the coaxial line.

Coupling analysis of transmission lines excited by space electromagnetic fields based on time domain hybrid method using parallel technique

We present a time domain hybrid method to realize the fast coupling analysis of transmission lines excited by space electromagnetic fields, in which parallel finite-difference time-domain (FDTD) method, interpolation scheme, and Agrawal model-based transmission line (TL) equations are organically integrated together. Specifically, the Agrawal model is employed to establish the TL equations to describe the coupling effects of space electromagnetic fields on transmission lines. Then, the excitation fields functioning as distribution sources in TL equations are calculated by the parallel FDTD method through using the message passing interface (MPI) library scheme and interpolation scheme. Finally, the TL equations are discretized by the central difference scheme of FDTD and assigned to multiple processors to obtain the transient responses on the terminal loads of these lines. The significant feature of the presented method is embodied in its parallel and synchronous calculations of the space electromagnetic fields and transient responses on the lines. Numerical simulations of ambient wave acting on multi-conductor transmission lines (MTLs), which are located on the PEC ground and in the shielded cavity respectively, are implemented to verify the accuracy and efficiency of the presented method.

Accurate Fault Location Modeling for Parallel Transmission Lines Considering Mutual Effect

:A new accurate algorithms based on mathematical modeling of two parallel transmissions lines system(TPTLS)as influenced by the mutual effect to determine the fault location is discussed in this work.The distance relay measures the impedance to the fault location which is the positive-sequence.The principle of summation the positive-,negative-,and zero-sequence voltages which equal zero is used to determine the fault location on the TPTLS.Also,the impedance of the transmission line to the fault location is determined.These algorithms are applied to single-line-to-ground(SLG)and double-line-to-ground(DLG)faults.To detect the fault location along the transmission line,its impedance as seen by the distance relay is determined to indicate if the fault is within the relay’s reach area.TPTLS under study are fed from one-and both-ends.A schematic diagrams are obtained for the impedance relays to determine the fault location with high accuracy.

Fault location for parallel transmission lines using one-terminal current traveling waves

With proper phase module transformation,parallel lines can be decomposed to the same directional net and the reverse directional net. The propagation characteristics of traveling waves in the reverse directional net were analyzed,and the refraction coefficient at the fault point for a single phase fault was derived. In addition,the module selection was discussed. Simulation results show that satisfying accuracy can be achieved with the proposed method. Moreover,it is immune to fault types,fault resistances,and outside system parameters.

Online One-End Fault Location Algorithm for Parallel Transmission Lines

Fault location and distance protection are essential smart grid technologies ensuring reliability of the power system. This paper describes an accurate algorithm for locating faults on double-circuit transmission lines. The proposed approach is capable of identifying the faulted circuit of a parallel transmission line by checking the estimated fault location and fault resistance. Voltage and current measurements from only one of the terminals of the faulty line are used. No pre-fault data are required for the estimation. The lumped parameter line model considering shunt capacitance is utilized for the derivation of the algorithm. It’s assumed that line parameters are known and transmission lines are fully transposed. The method is applicable to all types of faults. It’s evinced by evaluation studies that the proposed algorithm can correctly determine the faulted circuit in most cases. For exceptional cases, the current waveforms during the fault can be used to help identify the faulted circuit. The proposed algorithm generates quite accurate fault location estimates, and may be suitable for distance relaying.

Fault location of untransposed double-circuit transmission lines based on an improved Karrenbauer matrix and the QPSO algorithm

Some double-circuit transmission lines are untransposed,which results in complex coupling relations between the parameters of the transmission lines.If the traditional modal transformation matrix is directly used to decouple the parameters,it can lead to large errors in the decoupled modal parameter,errors which will be amplified in the fault location equation.Consequently,it makes the fault location results of the untransposed double-circuit transmission lines less accurate.Therefore,a new modal transformation method is needed to decou-ple the parameter matrix of untransposed double-circuit transmission lines and realize the fault location according to the decoupled modal parameter.By improving the basis of the Karrenbauer matrix,a modal transformation matrix suitable for decoupling parameters of untransposed double-circuit transmission lines is obtained.To address the dif-ficulties in solving the fault location equation of untransposed double-circuit transmission lines,a new fault location method based on an improved Karrenbauer matrix and the quantum-behaved particle swarm optimization(QPSO)algorithm is proposed.Firstly,the line parameter matrix is decomposed into identical and inverse sequence compo-nents using the identical-inverse sequence component transformation.The Karrenbauer matrix is then transformed to obtain the improved Karrenbauer matrix for untransposed double-circuit transmission lines and applied to identi-cal and inverse sequence components to solve the decoupled modal parameter.Secondly,based on the principle that voltage magnitudes at both ends are equal,the fault location equation is expressed using sequence compo-nents at each end,and the QPSO algorithm is introduced to solve the equation.Finally,the feasibility and accuracy of the proposed method are verified by PSCAD simulation.The simulation results fully demonstrate that the innova-tive improvement on the basis of the traditional modal transformation matrix in this paper can realize the modal transformation of the complex coupling parameters of the untransposed double-circuit transmission lines.It causes almost no errors in the decoupling process.The QPSO algorithm can also solve the fault location equation more accu-rately.The new fault location method can realize the accurate fault location of untransposed double-circuit transmis-sion lines.

端接复杂电路传输线网络的电磁耦合时域并行计算方法

针对端接复杂电路传输线(TL)网络的电磁耦合问题,仍缺乏高效的场路协同仿真技术。该文将传输线方程与时域有限差分(FDTD)方法、诺顿定理和置换定理以及NGSPICE软件相结合,并引入消息传递接口(MPI)并行技术,提出一种高效的时域混合并行算法(FDTDTL-NGSPICE)。首先,根据诺顿定理和置换定理,将传输线网络分解为传输线子系统和复杂电路子系统,并构建对应的等效电路模型。然后,使用FDTDTL并行算法计算传输线子系统沿线各点的电压和电流,并获取对应诺顿等效电路的电流源和等效导纳大小。最后,使用NGSPICE对复杂电路子系统进行传导干扰分析,获得复杂电路各元件上的瞬态响应,并将端口电压反馈给传输线子系统作为边界,实现传输线网络电磁耦合的场线路联合协同仿真。通过对3类典型场景的计算实例,分别使用时域混合并行算法和电磁仿真软件CST电缆工作室(CS)进行数值模拟并对比,验证所提算法的置信度。

750kV单回并行输电线路电磁辐射环境研究

采用《环境影响评价技术导则输变电》(HJ 24—2020)附录C、D推荐的计算模式对750 kV单回并行输电线路电磁辐射环境进行计算与预测。结果表明,经过耕地、园地、牧草地、畜禽饲养地、道路等场所,当导线对地最小高度为15.5 m时,单回并行线路下的工频电场强度最大值超过10 kV/m;需将导线对地最小高度提至16.5 m,才能满足4 kV/m控制限值要求。750 kV单回并行输电线路产生的工频磁场强度小于公众曝露控制限值(100μT),一般情况下不会成为线路建设的环境制约因素;但其产生的工频电场是电磁环境影响的主要因素,电场强度控制限值(4 kV/m)是线路建设的环境制约因素,同时也是输变电电磁环境重点控制因素。现场实测结果与理论预测结果符合性较好,表明采用的预测模式具有较好的应用性,研究结果可为750 kV单回并行输电线路的建设和环境监管提供支持。

一种基于CNN与FFT‑ELM的输电线路故障识别与定位方法

及时、准确地检测输电线路故障类型与位置是提高电力系统可靠性最重要的问题之一,为此提出一种基于卷积神经网络(convolutional neural networks,CNN)与基于快速傅里叶变换(fast Fourier transform,FFT)的极限学习机(extreme learning machine,ELM)分类模型并行的输电线路故障识别及定位方法。首先,以故障电压时序图作为输入,构建CNN;然后,利用FFT将时域故障电压数据分解,提取各频段的电压峰值与相角作为故障特征样本;接着,以提取的故障特征样本集作为输入,构建ELM网络;最后,通过特征融合层将2个神经网络进行融合,输出故障类型和定位结果。实验结果表明,此方法对输电线路故障识别的准确率为99.95%、故障定位误差在500 m以内、平均误差为263.5 m,可靠性优于其他模型。

交直流输电线路混合电场的人体感受试验及设计控制值研究

交直流输电线路同走廊和同塔架设是随着我国电网技术发展而出现的新输电方式,国内外尚无相应的交直流混合电场设计控制值标准。因此,设计同走廊和同塔架设的交直流输电线路时,导线对地高度和走廊宽度的选取面临无据可依的难题。该文提出确定交直流混合电场设计控制值的原则;开展不同交流(工频)电场和直流电场组合下的人体直接感受和暂态电击感受试验;通过对试验结果的统计分析,获得不同概率下人体不出现明显感受时的交流(工频)电场和直流电场关系曲线;在此基础上,得出确定交直流输电线路混合电场设计控制值的公式。该研究可为同走廊和同塔架设交直流输电线路设计中交直流混合电场的控制提供一定技术支撑。

Statistical Analysis of Radio Interference of 1000 kV UHV AC Double-circuit Transmission Lines in Foul Weather

Analyzing the impact of radio interference(RI)variation during foul weather conditions is an area that has received limited study.This paper provides a statistical analysis of RI measurements obtained from a long-term observation station close to the world’s first commercially operating 1000 kV UHV AC double-circuit transmission line in China.During six months of observations,the impact of RI was studied on the line during fog,drizzle,and light snow and rain.It was found that RI increases linearly with the natural logarithm of the precipitation intensity.The Levenberg-Marquardt algorithm(LMA)is employed to fit the RI value with the precipitation intensity.The reasonable distribution of RI in different foul weather is verified by one-sample K-S test.This test is seen as beneficial for further RI prediction based on statistical weather mode.

基于改进Cascade RCNN的输电线路防振锤脱落检测方法

无人机巡检输电线路时,因拍摄角度和距离问题,容易出现被输电线遮挡和远距离拍摄的防振锤脱落目标,导致目标特征被遮挡且分辨率较低,且部分防振锤出现滑移现象,导致目标识别准确率降低。针对以上问题,提出一种基于改进Cascade RCNN的防振锤脱落检测网络。第一,设计了对比学习网络,将正负样本与真实样本的特征进行对比学习,利用对比损失函数训练网络,使其能更加关注到被遮挡的防振锤脱落目标,提升其特征提取能力;第二,进行了分类器增强操作,筛选出网络级联结构中回归效果较好的感兴趣区域并送入最后的分类回归队列中,提高了分类器的分类能力,进而提升检测目标的分类分数;第三,设计了并行注意力机制模块,整合网络提取的特征,增大关键特征的权重,使网络关注到图像中更关键的区域;在特征金字塔中,将双线性插值方法代替为反卷积,提升特征还原能力。经交叉验证实验结果表明,改进后的模型召回率、精确率和平均精度达到了97.5%,91.0%和92.0%,相比基线模型分别提高了6.9%,28.4%和8.0%。

特高压输电线路检修工况下感应电压与电流计算分析

针对特高压输电线路在检修工况下因受同塔或临近运行导线的影响,面临严重的电磁感应问题,建立了检修导线挂接地线前的感应电压及挂接地线后的感应电流计算模型,定量地研究了输送功率、并行长度、并行间距、杆塔接地电阻等参数对上述感应电压及感应电流的影响规律和影响程度,并建立±1100 kV吉泉线的实际工况模型,计算分析了吉泉线在检修工况下沿线的感应电压、感应电流幅值和分布规律。研究结果为特高压输电线路的检修作业,以及特高压输电线路检修用消弧接地线的参数选型提供了依据。

Effect of Different Arresters on Switching Overvoltages in UHV Transmission Lines

The amplitude of switching overvoltages is a key factor for designing the insulation of UHV equipment. The effect of different arresters needs to be studied, since installing arresters is an important way to suppress switching overvoltages in UHV transmission lines. Switching overvoltages on the 1000 kV Huainan-Huxi double-circuit transmission line were simulated for different operating modes and different arrester designs using the electromagnetic transient program PSCAD/EMTDC. With parallel resistors, the switching overvoltages are less than 1.70 p.u. （1.0 p.u.=1100×√ 2 /√3 kV）. If the arrestors are better, the switching overvoltages can be reduced even lower to 1.55 p.u. Without parallel resistors, the arresters can reduce three-phase energizing overvoltages to 1.70 p.u, while the single-phase reclosing overvoltages still exceed the limit. The results show that the parallel resistors cannot be eliminated if the arresters are only installed at each end of the transmission line. Also, better quality arresters significantly lower the switching overvoltages.

多回输电线路并架的不平衡性分析

以卡森模型为基础 ,对一段 2km未换位的同杆并架 4回输电线及避雷线的试验线路 ,用Matlab仿真计算了序参数及线路不平衡度。根据序参数计算结果研究了实际线路参数对各类不平衡系数的影响规律及特性 ,其主要影响因素有导线相序排列方式、导线对地高度、导线间距离以及导线自身属性等。分析结果表明 。

基于分布参数的同杆双回线单线故障准确测距原理

针对同杆双回线线间联系紧密,不能忽略线间分布电容对测距结果的影响,该文在同杆双回线分布参数模型下,利用相序变换后双回线反向网络图中不存在系统参数的优势,提出了一种使用单端工频电气量进行故障测距的算法,该算法从原理上解决了系统阻抗及过渡电阻对测距的影响,克服了目前同杆双回线不能精确定位的问题。该算法理论分析简单,迭代求解测距方程不存在伪根问题,ATP仿真结果表明该算法具有很高的测距精度。

特高压交流输电线路正常运行时对输油输气管道的感性耦合计算模型

随着我国经济的持续增长,交流输电线路对输油输气管道的电磁影响问题日益突出。基于管道-大地回路传输线模型,获得了交流输电线路正常运行时在输油输气管道上产生的感性耦合电压的解析表达式。经过严格推导,提出了管道两端接匹配阻抗时管道饱和平行长度的概念,即随着管道平行长度的增大,管道感性耦合电压先逐渐增大,然后略有降低,并最终基本趋于稳定。通过仿真计算,拓展了线路与管道斜接近时等效接近距离现有经验公式的适用范围,计算误差可控制在5%以内。研究成果可供电力部门和石油管道部门进行管道安全评估或确定管道与线路的最小安全距离。

绝缘子串并联间隙的工频大电流燃弧试验

绝缘子串雷闪或污闪后,后续的工频电弧会烧伤甚至损坏绝缘子,为此研究了用于保护绝缘子的并联间隙防雷保护装置。介绍了并联间隙防雷保护在国内外的研究和应用状况,采用自己研制的样品研究了结构简单、安装方便适用于110kV和220kV等级V型悬垂绝缘子串和I型悬垂绝缘子串的并联间隙防雷保护装置;充分考虑电网未来发展需求后确定了具体的试验方案且110kV和220kV绝缘子串并联间隙试验的短路电流均为50kA,短路持续时间均为0.2s。在西安高压电器研究所大容量检测试验室对样品进行的大电流燃弧试验证明,沿绝缘子串表面产生的50kA工频电弧约0.01s的时间便可移动到招弧角端部灼烧;招弧角可耐受50kA工频电弧持续燃烧0.2s并能保护绝缘子免受电弧灼烧。因此,绝缘子并联间隙防雷方式是一种合理有效的防雷保护措施,值得在我国输电线路上推广应用。

二平行传输线间的串扰分析

对共地平行传输线间的串扰耦合进行分析 ,得出耦合响应与信号频率、线间距及线距地高度的关系 ,给出电子电路设计中传输线布设的原则。并对 PCB布线提出参考。

基于双回线环流的时域法故障定位

该文提出了一种利用双端电流量实现双回线故障定位的时域测距算法。该算法利用双回线环流网与两侧系统无关且两端电压为零的特点,只用线路两端的电流量,就可计算出环流网的沿线电压分布,并根据从两端计算得到的电压分布差值在故障点处最小的原理实现测距。由于避免了使用电压量,故该测距原理不受电容式电压互感器档缪乖萏藕诺南拗?该算法能够利用故障全过程的任何一段数据实现测距,且该算法所需数据窗短,只要略大于被测线路传输时间的 2 倍即可。该算法采用分布参数线模,克服了忽略线路电容带来的误差,适用于高压长距离输电线。仿真结果表明:测距误差将小于 0.15km,且测距精度不受故障类型和过渡电阻的影响。