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.

SELECTION OF TRANSMISSION LINE MODELS USED IN POWER SYSTEM TRANSIENT SIMULATIONS

A method used for determining the number of equivalent π sections oftransmission line model according to the frequency range of interest and the model accura-cy defined herein is proposed.Factors influencing the discrepancies between continuous ordistributed parameter and multiple π or lumped parameter models are discussed.Generalconclusions concerning the π section lengths of line models used in transient stability,faulttransient and switching over-voltage studies are drawn.Time-domain simulation resultsconfirm the effectiveness of this method.

Minimization of Electric Power Losses on 132 kV and 220 kV Uganda Electricity Transmission Lines

The classical minimization of power losses in transmission lines is dominated by artificial intelligence techniques, which do not guarantee global optimum amidst local minima. Revolutionary and evolutionary techniques are encumbered with sophisticated transformations, which weaken the techniques. Power loss minimization is crucial to the efficient design and operation of power transmission lines. Minimization of losses is one way to meet steady grid supply, especially at peak demand. Thus, this paper has presented a gradient technique to obtain optimal variables and values from the power loss model, which efficiently minimizes power losses by modifying the traditional power loss model that combines Ohm and Corona losses. Optimality tests showed that the unmodified model does not support the minimization of power losses on transmission lines as the Hessian matrix portrayed the maximization of power losses. However, the modified model is consistent with the gradient method of optimization, which yielded optimum variables and values from the power loss model developed in this study. The unmodified (modified) models for Bujagali-Kawanda 220 kV and Masaka West-Mbarara North 132 kV transmission lines in Uganda showed maximum power losses of 0.406 (0.391) and 0.452 (0.446) kW/km/phase respectively. These results indicate that the modified model is superior to the unmodified model in minimizing power losses in the transmission lines and should be implemented for the efficient design and operation of power transmission lines within and outside Uganda for the same transmission voltages.

Optimal design scheme based on the segmental transmission line methodology for high-frequency interconnection in 3D micro/nano integration

With the continuous growth of signal frequency and package density, discontinuity of the high-frequency interconnection in 3 D micro/nano integration becomes unavoidable, which results in serious signal integrity problems. Traditional interconnection design schemes, such as termination and shielding/isolation, cannot meet the requirements under the unified constraints of specific cost, space occupancy, and performance. In this study, a transmission line design optimization scheme based on the segmental transmission line(STL) methodology is proposed. The genetic algorithm is used to select the optimal segment structure parameters of the transmission line to construct an STL with satisfying transmission performance or meet the specific signal amplitude adjustment requirements. This scheme can be adapted to various signal transmission scenarios to significantly improve the signal loss caused by reflection or other negative electromagnetic factors and meet the requirements for the modeling of discontinuous transmission lines. The simulation results show that this scheme is effective in the design scenario of performance improvement or equivalent modeling of discontinuous transmission lines and has significant advantages in circuit area reduction.

A Modeling Method for Transformer Windings Under VFTO Based on S-parameters

To study the Very Fast Transient Over-voltage (VFTO) distribution in transformer windings in gas insulated substation (GIS), a systematic methodology based on S-parameters is presented for establishing high-frequency model of transformer windings. Firstly, voltage transfer functions are derived from S-parameters which are calculated or measured from transformer windings. Secondly, voltage transfer functions are fitted with rational functions by the vector fitting method and then the rational transfer functions are order-reduced by optimal Pade-approximation algorithm. Lastly, the resultant voltage transfer functions are synthesized by network technology. Computational results are consistent with simulation results of Electromagnetic Transient Program (EMTP) and confirm the feasibility and validity of proposed methodology.

Impact of Weather Conditions and Dynamic Load Models on Steady State and Dynamic Response of Power System

This paper gives an insight on the effect of transmission line temperature variations, resulting from loading and weather conditions changes, on a power system＇s steady state and dynamic performance. The impact of dynamic load models on system stability is also studied. The steady-state and dynamic stability simulation results of a 39 bus system for constant line impedance （the traditional simulation practice） are compared to the results with estimated, but realistic, temperature varied line impedances using PSLF （positive sequence load flow） software. The modulated line impedances will affect the thermal loading levels and voltage profiles of buses under steady state response, while the dynamic results will show improved damping in electro-mechanical oscillations at generator buses.

基于AR谱估计和Adaline神经元的间谐波分析

将人工神经网络应用于电力系统间谐波分析,提出了Burg算法与Adaline神经元相结合的间谐波分析方法。通过Burg算法计算自回归(AR)模型参数,得到信号中谐波和间谐波的个数及频率初值,然后应用改进的Adaline神经网络精确分析谐波和间谐波的频率、幅值和相位。MATLAB仿真结果验证了Burg-Adaline间谐波分析方法具有分辨率高、精度高、收敛快的优点。

Numerical Analysis of the Output-Pulse Shaping Capability of Linear Transformer Drivers

Output-pulse shaping capability of a linear transformer driver （LTD） module under different conditions is studied, by conducting the whole circuit model simulation by using the PSPICE code. Results indicate that a higher impedance profile of the internal transmission line would lead to a wider adjustment range for the output current rise time and a narrower adjustment range for the current peak. The number of cavities in series has a positive effect on the output- pulse shaping capability of LTD. Such an improvement in the output-pulse shaping capability can primarily be ascribed to the increment in the axial electric length of LTD. For a triggering time interval longer than the time taken by a pulse to propagate through the length of one cavity, the output parameters of LTD could be improved significantly. The present insulating capability of gas switches and other elements in the LTD cavities may only tolerate a slightly longer deviation in the triggering time interval. It is feasible for the LTD module to reduce the output current rise time, though it is not useful to improve the peak power effectively.

Influences of Switching Jitter on the Operational Performances of Linear Transformer Drivers-Based Drivers

A whole circuit model of a linear transformer drivers （LTD） module composed of 60 cavities in series was developed in the software PSPICE to study the influence of switching jitter on the operational performances of LTDs. In the model, each brick in each cavity is capable of operating with jitter in its switch. Additionally, the manner of triggering cables entering into cavities was considered. The performances of the LTD module operating with three typical cavity-triggering sequences were simulated and the simulation results indicate that switching jitter affects slightly the peak and starting time of the output current pulse. However, the enhancement in switching jitter would significantly lengthen the rise time of the output current pulse. Without considering other factors, a jitter lower than 10 ns may be necessary for the switches in the LTD module to provide output current parameters with an acceptable deviation.

基于随机森林优化RL的电力工程造价预测

针对现阶段电力工程造价数据预测准确度较低的问题,提出了一种基于随机森林优化RL的相关预测算法。通过分析影响电力工程造价的因素,将其按照影响程度的大小进行分级,利用随机森林算法加以筛选,并采用筛选后的影响因素特征向量作为预测模型的训练和测试数据。同时,将电力工程造价预测问题转化为输电线路规划问题,再使用强化学习优化蚁群算法的参数来构建电力工程造价预测模型。经过实验对照,综合两种栅格尺寸结果,所提方案比两种对照组算法的电子工程造价分别降低了2.97%、3.78%。

多谐波源接入的城市配电网SAPF优化配置方法

针对分布式光伏和电动汽车充电设施等新谐波源渗透率高及分散接入造成的城市配电网谐波污染分散化与全网化问题,构建一种兼顾配电网谐波治理成本与治理成效的并联型有源电力滤波器选址定容双层优化模型。首先,外、内层模型分别以配电网谐波治理成本最小和电压畸变率最低为目标函数;然后,采用粒子群优化算法和遗传算法分别求解,实现配电网谐波治理效益最高的目标;最后,选取IEEE 33节点系统进行仿真,验证了所建模型对配电网谐波治理装置优化配置的有效性。

基于智能预警技术的输电线路在线巡视方法

针对常规技术对输电线路在线巡视效率低下、误差率高的问题,提出了基于智能预警技术的输电线路在线巡视方法,设计一套基于5G通信和无线数据通信技术的输电线路在线智能预警系统,通过ARM+DSP双核处理器实现输电线路故障识别。采用无人机技术实现高空输电线路巡检,通过改进型蚁群算法模型实现输电线路故障检测,并设计了故障检测定位技术,利用融入行波定位技术的蚁群算法模型提高了输电线路在线巡视能力。实验表明,方法定位精确、误检率低,具有一定的实际应用价值。

基于动态平衡布局的输电网潮流图自动生成方法

为解决输电网潮流图自动生成中厂站布局与线路布线问题,提出基于动态平衡布局的输电网潮流图自动生成方法。针对厂站布局,首先,在力导向算法的基础上引入基于图纸中心点的惩罚函数,以解决力导向算法布局不均匀的问题,提高布局的均布度;然后,利用厂站分布率参数控制算法平衡次数,引导厂站向图纸边界运动,解决布局自动适应给定图幅大小的问题;最后,通过位置映射变换将围绕图纸中心点的椭圆分布转换为矩形分布,解决引入惩罚函数布局均匀但不符合传统输电网潮流图绘制习惯的问题。针对线路布线提出以构建通道树为中心的布线方法,有效降低布线交点个数,提升布线效果。所提布局与布线算法在实际工程应用中取得了良好的效果,通过案例验证了输电网潮流图自动生成的正确性和有效性。

时间累积架空输电线路覆冰预测模型与算法综述

在覆冰条件的气象因素下,输电导线随时间累积形成的覆冰厚度、形状和分布变化,影响着电网系统的安全运行。按预测模型从覆冰生长到导线除冰各阶段存在的关联分析,讨论了各模型的优势差异以及相互存在组合的可能性。覆冰全周期存在着由微观到宏观的变化,影响着导线覆冰的生长进程。预测模型可按全周期组合,首先,对初始数据的降噪可解决数据发散,用主成分分析法的降维可提高预测精度。其次,模型中的支持向量机、混合的群智能优化算法、遗传算法组合等工具乃至交叉方式,都着力于覆冰过程的辨识与建模。再次,将热力融冰技术的负荷交流或涡流自热环应用在除冰阶段,使覆冰监测形成了动态闭环系统。最后,结合分析对输电线路覆冰预测的研究方向做了展望。

带散射体的电力系统多级传输线高频耦合模型

高频电磁场会与架空输电线路产生耦合,一旦高频电磁场的波长小于传输线的高度,经典传输线理论就不再适用。传统的全波数值算法虽然可以解决这一问题,但求解效率不高,需要消耗大量的时间与计算资源。此外,电力系统输电线路往往有多个垂直端,线路布局复杂,而以往针对电力系统传输线的高效求解研究都是只有左右两个垂直端的较为简单的模型,与实际电力系统传输线的结构不符,没有考虑中间带有垂直端的情况。为了解决这些问题,文中提出一种理论有效的方法来解决有损耗地面上方带有散射体的电力系统多级传输线的高频电磁场耦合问题。采用计算效率高的渐近法,并在渐近法中引入散射体的概念,以考虑更复杂的电路结构。最后通过数值算例验证了该方法的准确性和有效性。

结合ECC算法的电力监控网络智能接入协议

为了进一步降低电力监控网络遭受攻击的风险,基于ECC公钥加密算法,提出了具有较高安全性能的智能接入协议。通过研究电力监控网络的基本架构和安全体系,总结了电力监控终端所面临的多种攻击方式。并在此基础上,利用ECC公钥加密算法,深度改进适用于电力监控网络的智能接入协议,进而优化协议的加密耗时、解密耗时及安全强度等多项参数。仿真结果表明,与基于RSA算法的协议相比,基于ECC算法的智能接入协议具备更高的安全强度。

基于TCP/IP协议与关联规则的电力监控系统多线程通信方法

电力监控系统环境中存在过多噪声因素干扰,导致通信效率和质量低。为此,提出一种基于传输控制协议/网际协议(transmission control protocol/internet protocol,TCP/IP)与关联规则的多线程通信算法。将背景噪声看作电力监控信号的突变现象,查找回应突变函数的信号值,利用谐波分离算法,去除背景噪声。根据不同线程的传输特点,采用TCP/IP协议建立通信程序包,分别设置句柄、终止、挂起以及执行函数,为不同线程的通信数据,匹配不同的通信协议。试验结果证明:对电力监控系统源设备的传输信号多线程通信时,通信信号波频变化最为平稳,在0~2000 s的采样区间内,未出现传输为0现象;对背景噪声去噪后,波形相比原始信号变化明显较为稳定,没有出现过高或过低的幅值变化。所提方法通信信号表达平稳、效率较高,对原始信号的保留效果较好,去噪能力很强。

Wide band modeling of large power transformer windings for very fast transient overvoltage (VFTO) analysis

There are some difficulties in using multi-transmission-line (MTL) model for wide band modeling of whole windings of the large power transformer. In this paper, the normalized MTL model is firstly de- rived, with which not only the difficulty of modeling windings with different turn-lengths using MTL can be solved, but also the model can be extended to the modeling of the multi-winding transformer. Secondly, both MTL model and the lumped circuit model on turn basis are mathematically compared in validation of the frequency range and it is pointed out that the lumped circuit model on turn basis is generally valid below 2.5 MHz for EHV and UHV power transformers. Finally, based on the MTL equations, a novel lumped circuit model is derived and it is shown that the valid frequency range of the new circuit is extended to about 4 MHz for modeling large EHV and UHV power transformer windings.

基于多导体传输线理论的配电网电力电缆载波模型降阶分析

为降低配电网电力电缆载波模型复杂程度,首先,根据配电网常用三芯XLPE绝缘电力电缆结构,结合电力电缆三相金属护套相互接触的实际,以三相金属护套为整体进行分析,将电力电缆7阶多导体传输线载波模型降为5阶。接着,根据配电网终端电力电缆金属护套、铠装直连接地的特点,将其进行等效处理,并分析了等效单位长度参数矩阵各元素与实际参数的关系,再次将配电网电力电缆5阶载波模型降为4阶。仿真试验验证了降阶分析的正确性,电力电缆载波模型的两次降阶,显著降低载波模型复杂程度,降低运算量提升分析速度,为载波通信在电力电缆传输中的进一步分析提供参考。

Mitigation of Transients in Capacitor Coupled Substations Using Traditional RLC Filter Techniques

This article presents an extensive examination and modeling of Capacitor Coupled Substations (CCS), noting some of their inherent constraints. The underlying implementation of a CCS is to supply electricity directly from high-voltage (HV) transmission lines to low-voltage (LV) consumers through coupling capacitors and is said to be cost-effective as compared to conventional distribution networks. However, the functionality of such substations is susceptible to various transient phenomena, including ferroresonance and overvoltage occurrences. To address these challenges, the study uses simulations to evaluate the effectiveness of conventional resistor-inductor-capacitor (RLC) filter in mitigating hazardous overvoltage resulting from transients. The proposed methodology entails using standard RLC filter to suppress transients and its associated overvoltage risks. Through a series of MATLAB/Simulink simulations, the research emphasizes the practical effectiveness of this technique. The study examines the impact of transients under varied operational scenarios, including no-load switching conditions, temporary short-circuits, and load on/off events. The primary aim of the article is to assess the viability of using an established technology to manage system instabilities upon the energization of a CCS under no-load circumstances or in case of a short-circuit fault occurring on the primary side of the CCS distribution transformer. The findings underscore the effectiveness of conventional RLC filters in suppressing transients induced by the CCS no-load switching.