New Method of Measuring the Positive-sequence Capacitance of T-connection Transmission Lines

A novel method of measuring the positive-sequence capacitance of T-connection transmission lines is proposed. The mathematical model of the new method is explained in detail. In order to obtain enough independent equations, three independent operation modes of T-connection transmission lines during the line measurement are introduced. The digital simulation results and field measurement results are shown. The simulation and measurement results have validated that the new method can meet the needs of measuring the positive-sequence capacitance of T-connection transmission lines. This method has been implemented in the newly developed measurement instrument.

Study on Fault Location in the T-Connection Transmission Lines Based on Wavelet Transform

The results of T-Line Traveling Wave Fault Location is easily influenced by the wave arrival time and traveling wave propagation velocity;it proposes that the traveling wave uses wavelet transform to extract the modulus maxima of breakdown voltage, to confirm the time of the traveling wave reaching the three-terminal line. The speed of the traveling wave reaching three terminals is confirmed by the structural parameters of the transmission line. We apply the arrival time and propagation velocity to the T-type traveling wave fault location algorithm. Different transmission line distance select the corresponding algorithm, excluding the impact of fault branches and in some cases ranging accuracy, the failure dead zone will not appear. After MATLAB simulation analysis, the algorithm analysis is clear;the range accuracy is high, so that it can meet the requirements of fault location.

Deep Myofascial Kinetic Lines in Horses, Comparative Dissection Studies Derived from Humans

Seven superficial myofascial kinetic lines have been described earlier in horses in a comparative dissection study to the human lines. The lines act as an anatomical basis for understanding locomotion, stabilization, and posture. Further dissections verified three profound equine lines comparable to those described in humans and a fourth line not described previously. Forty-four horses of different breed and gender were dissected, imaged and video recorded. The horses were euthanized due to reasons not related to this study. A Deep Ventral Line (DVL) very similar to that in the human was verified in these studies. The line spans from the insertion of the profound flexor tendon in the hindlimb to the base of the cranium and oral part of the cavities of the head. It includes the profound, hypaxial myofascial structures, the ventral coccygeal muscles, the psoas muscles, the diaphragm, the longus colli/capitis muscles and the ventral capital muscles. The inner lining of the pelvic, abdominal and thoracic cavities with all the organs, vessels and nerves are also included. The line is closely connected to the autonomic nervous system by the vagus nerve, the pelvic nerves, the sympathetic trunk and several of the prevertebral nerves and ganglia. The new line identified in this study, is a Deep Dorsal Line (DDL), which starts in the dorsal tail muscles. It comprises myofascial structures of the spinocostotransversal system from the tail to the head including the nuchal ligament. It connects to the dura mater and has a major role in controlling the motion and stabilization of the Columna vertebralis. Both the DDL and the DVL include the coccygeal myofascia and periosteum of the skull. Due to differences in biped and quadruped anatomy the Front Limb Adduction Line (FADL) and the Front Limb Abduction Line (FABL) differ from the human lines. The lines are identified as slings in the brachial and antebrachial regions. The FABL includes structures for abduction and internal rotation connecting to the Front Limb Retraction Line (FLRL), and the FADL structures of adduction and external rotation in close proximity to the Front Limb Protraction Line (FLPL). The front limb lines support the movement of the front limb around the “thoraco-scapula pivot joint” medially at the level of the upper third of the scapula. The DVL identified in this study is similar to the human DFL whereas the front limb lines differ somewhat from the deep human arm lines due to differences in bi- and quadruped anatomy and biomechanics. We have identified and described this new equine DDL. The lines altogether explain a profound body balance and confirm the three-dimensional equine fascial network, which is of great clinical and biomechanical importance.

Study of Steady-state Performances for a Novel Line-start Single-phase Permanent Magnet Synchronous Motor With Three Parallel-connected Windings

对于三相感应电动机的单相运行,学者们已经提出了多种实用的接线方式,比如Smith接法、SEMIHEX接法。然而,对于三相异步起动永磁同步电动机的单相运行,很少有合适的接法提出。将并联式接法应用于三相异步起动永磁同步电动机的单相运行,提出了一种新型三绕组并联式异步起动单相永磁同步电动机。分析了三相异步起动永磁同步电动机同步运行时以及起动瞬间的正序、负序阻抗,基于对称分量法,对该接法电机的对称运行条件进行分析,得出了电容的确定方法,并利用遗传算法对电容值进行优化。提出了该新型电机稳态性能的计算方法;设计了一台高功率因数和一台低功率因数三相异步起动永磁同步电动机作为样机,并分别将其改接为三绕组高效单相永磁同步电动机,进行实验研究。实验结果表明,低功率因数的异步起动永磁同步电动机更适合改接成新型三绕组并联式单相永磁同步电动机。由低功率因数三相永磁同步电动机改接成的单相异步起动永磁同步电动机在额定负载下运行时,具有与同容量三相永磁同步电动机相近的效率和更高的功率因数。

Over Voltage Fault due to Disconnection of Consumer’s Transformer Neutral Wire

Practically,the load currents in three phases are asymmetric in the power system.It means that the impedances are different in all three phases.If the consumer’s transformer neutral cut off and/or was disconnected from the neutral of power supply source,then there will be some trouble and failure occurred.The current in the neutral wire drops down to zero when the neutral wire is cut off and the phase currents of all three-phase equal to each other since there was no return wire.The currents are equal but the voltages at the phase consumers are different.Especially for residential single-phase consumers,the voltage at the consumers of the phase varies differently for three phase systems when the neutral wire was disconnected at consumer side and even the voltage at the consumers one or two of those three phases becomes over nominal voltage or reaches nearly line voltage.In this case,the electronic appliances in that phase will be fed by high voltage than the rated value and they can be broken down.In the power system of UB(Ulaanbaatar)city,there are some occasional such kind of failures every year.Obviously,many electronic appliances were broken down due to high voltage and the electricity utility companies respond for service charge of damaged parts.

时速120 km地铁快线空气动力学试验研究

为探明设计时速120 km快速地铁列车在多区段桥隧衔接线路运行时的气动效应和气密性能,采用实车试验的方法,在武汉某多区段桥隧衔接地铁快线对某4车编组的新研A型密封性地铁列车开展空气动力学测试。实验测试系统采用LL-250-15A型Kulite压力传感器,通过测量列车外部和内部的瞬态压力变化,分析全线路车外压力波动特性,对比沿列车长度方向不同测点位置的压力变化幅值,并分析不同空调状态下的车内压力舒适性。经过3次实验测试分析,该实验的结果具有可重复性。研究结果表明:全线路运行时,列车在隧道段内加减速导致车外压力变化幅值明显大于高架段,气动效应最恶劣的位置为地下段人防门变截面处,列车上行通过该处时车外任意3 s内压力变化幅值为1 071 Pa,下行通过该处时车外任意3 s内压力变化幅值为905 Pa;相对于下行线全线路,上行线车外任意3 s内压力变化幅值大18.3%;列车正线运营时压力波保护阀会在压力变化剧烈区段进行动作响应,列车上行时,空调开启、压力波保护阀正常启用状态下,车内任意3 s内压力变化幅值相对于压力波保护阀打开未启用时减少了16%,下行时,减少了28%,空调压力波保护阀能够有效降低车外压力波动对车内气压变化的影响。本文研究成果可为快速地铁线路设计、地铁列车运营及地铁气密性优化提供参考依据。

基于PCSA-YOLOv7 Former的输电线路连接金具及其锈蚀检测方法

输电线路分布情况复杂且故障难以有效检测,其中连接金具长期暴露于复杂环境下易受到恶劣环境的影响出现锈蚀等故障。针对输电线路连接金具部件具有尺度多样性和存在着锈蚀故障检测精度低的问题,提出了一种基于双重注意力嵌入重构和Swin Transformer的输电线路连接金具组件及其锈蚀故障检测方法:PCSA-YOLOv7 Former。实验结果表明:该方法在构建的TLCF数据集上的综合检测性能领先于12类当前先进的目标检测算法,其中在测试集上的mAP_(0.5)达到94.9%,该方法相比于基线模型YOLOv7,其F1和mAP0.5指标分别提升了2.6个百分点和2.2个百分点,说明该方法能够更全面地理解输电线路连接金具图像中的多尺度语义信息并学习到不易区分的微小细节表征。

Impedance-based Stability Criterion for the Stable Evaluation of Grid-connected Inverter Systems with Distributed Parameter Lines

For a multi-inverter grid-connected system,the stability of the point of common coupling(PCC)voltage is evaluated considering the distribution parameters of the transmission lines.First,the systems on both sides of the PCC are equalized,a smallsignal equivalent circuit similar to the“current source-grid”is established,and a mathematical model for the voltage of the PCC is derived.Then,using Euler’s formula and Nyquist stability criterion,the PCC voltage stability of the grid-connected system is evaluated by the impedance analysis method under the premise that the single-side excitation is stable.In addition,the gridconnected conditions causing PCC voltage instability are studied.A phase compensation method based on an impedance phase compensation control strategy is introduced.The stability of the grid-connected system is improved by compensating the phase margin at the equivalent impedance crossover-section frequency on both sides of the grid-connected system PCC.Finally,a simulation circuit is built to simulate and analyze the proposed model and phase compensation method.The simulation results verify the accuracy and effectiveness of the theoretical analysis.

直连绳索取心钻杆分区热处理技术研究

为了提高绳索取心钻杆的性能,对直连绳索取心钻杆的受力情况、结构特点以及传统处理工艺进行分析,提出了分区热处理的工艺。通过对两端进行热加工处理,使钻杆中间管体区域和两端热处理螺纹区域性能出现差异,提高两端综合强度的同时改善螺纹部分的受力状态,可使钻杆柱既具有高强度又兼具柔性,大幅提高钻杆机械性能以及耐磨性。其中调质硬度HRC33~38能在保证管体延伸率与正火、回火基本一致的情况下,强度提高37.7%,硬度提高40%,抗冲击性提高46.7%。调质硬度HRC38~42时,材料的耐磨性提高9.1%。更适合全液压钻机施工及深孔钻进,为钻探施工提供了钻机、钻杆配套性的优选方案。

基于衰减指数的主动配电网纵联保护新方法研究

根据光伏并网系统中光伏与大系统电源故障输出特性的差异,提出一种基于电流衰减指数的主动配电网保护新原理.首先对采集的保护线路首、末端电流进行滤波、去噪,以避免噪声造成Prony计算不精确的问题;再将线路首、末端电流衰减指数作差与给定门槛值比较,以便判断故障区域;最后通过改变故障位置、故障距离以及光伏渗透率,验证该方法在不同情况下的适用性.通过Matlab仿真实验表明本文提出的方法能够准确判断线内、线外故障,并且其对判断故障相有一定效果.

输电线路塔架结构连接节点加固研究

为解决输电线路塔架上部结构与基础连接节点加固的关键问题,采用ABAQUS建立该节点有限元实体单元模型,并考虑自然灾害下不同受力工况,并与原规范和现行规范的计算结果进行对比。研究结果表明,考虑上部结构加固后,该节点最薄弱处为靴板与主材连接螺栓剪切破坏,整体承载力裕度需加强。由此提出在不停电施工前提下,与上部结构主材加固型式匹配的节点加固方案,并通过实际试验进行了验证。节点加固研究成果有利于提高输电线路使用价值,也为同类装配式建筑节点加固研究提供了新思路。

复杂背景下航拍图像输电线提取算法研究

针对提取航拍图像中输电线容易出现断裂、重叠,识别准确率低等问题,提出一种改进Hough变换输电线提取算法。通过灰度化对航拍图像进行预处理,Canny算法识别输电线边缘;利用去除小连通区域方法减少边缘图像背景噪声;改进Hough变换参数空间的极大值判定范围,实现单直线响应准则。实验结果表明,改进算法相对于LSD、EDLines、传统Hough变换方法,能够完整提取出输电线,并且准确率高、抗噪性好。

高棒线氮气节约优化改造实践

高棒线轧材生产线上使用氮气点较多,气体消耗量大,吨钢耗氮成本高,存在很多浪费的现象。通过优化改进氮气排出控制系统,并对可以置换成压缩空气的使用场景进行置换,节约了大量氮气资源。改造后,可以降低氮气消耗水平,降低生产成本,提高能源利用水平,达到了保障生产、节能降耗的目的。

燃气电厂主接线优化方案探讨

电气主接线是发电厂电气设计的首要部分,也是构成电力系统的重要环节。本文分析大中型火力发电厂不同的接线型式,通过断路器检修、单一回路故障以及一回路故障另一断路器拒动几种工况的分析,对比不同主接线型式的可靠性;通过分析主接线调度、检修及扩建时的差异,对比不同型式主接线的灵活性;通过设备选型及数量、占地面积情况,对比不同主接线型式的经济性。通过对主接线可靠性、灵活性和经济性的比选,为同类型发电厂主接线设计提供思路及参考。

高速铁路改线工程拨接技术研究

高速铁路改线通常面临既有铁路运输调配难、专业性强、技术要求复杂、施工难度大等问题。改线施工涉及既有地道拆除、工作坑开挖、箱涵顶进、接触网施工等诸多环节,工程中采取合理的施工方案是保证工程质量的重要环节。针对线路拨接过程中施工复杂、天窗时间短等特点,对改线过程中施工技术和方法进行研究总结,确保铁路运输和工程建设的有序进行,为高速铁路改线施工提供参考和借鉴。

分网接入方式下LCC-HVDC系统运动方程模型及交互振荡模式的阻尼特征(二):交互振荡模式研究

为研究分网接入方式下电网换相换流器高压直流输电(line commutated converter based high voltage direct current,LCC-HVDC)系统的交互振荡模式及阻尼特征,基于系统的状态空间模型及系列文章(一)建立的运动方程模型,提取了表征逆变侧电气与控制环节强耦合特性的多个弱阻尼交互振荡模式,研究了不同短路比工况下交互振荡模式的变化特征。在此基础上,通过复转矩系数法量化评估了整流侧/逆变侧内部自稳性路径及双极交互作用致稳性路径对主导交互振荡模式阻尼特性的贡献度。结果表明:1)不同短路比工况下交互振荡模式的阻尼比会进行重新分配;2)当逆变侧正负极短路比相差较大时,双极交互作用较弱,正负极系统的稳定性由2个交互振荡模式各自主导,且稳定性特征有所差异;3)当逆变侧正负极短路比相近时,双极间动态交互加强,交互振荡模式会同时主导参与系统两极的稳定性,正负极稳定性特征相似。

分网接入方式下LCC-HVDC系统运动方程模型及交互振荡模式的阻尼特征(一):扰动传递路径分解

与常规直流相比,永富直流逆变站存在功率全送和功率分送运行方式,而其处于分网接入方式时电网换相换流器高压直流输电(line commutated converter based high voltage directcurrent,LCC-HVDC)系统的交互振荡模式及特征尚不明确。针对这一特殊运行方式,采用模块化建模的思路建立可以反映系统电气/控制回路间交互耦合路径的运动方程模型。在此基础上,依据系统整流侧-逆变侧、正极-负极间的交互耦合路径分解得到影响系统主导模式稳定性的3条扰动传递路径,即整流侧内部自稳性路径、逆变侧内部自稳性路径、双极交互作用致稳性路径。最后,设置不同工况下的案例,量化评估不同作用路径提供的阻尼大小,并通过仿真验证运动方程模型及扰动传递路径分析结果的正确性,为后续研究分网接入方式下LCC-HVDC系统交互振荡模式的阻尼特征提供模型基础。

珠海北停车场平面布置方案研究

随着城市建设发展,城市轨道交通车辆基地由于占地规模大,其面临的用地受限问题日益突显。以南中珠城际珠海北停车场为例,选址位于铁路水系合围地块,周边控制因素较多,如何确定经济合理的平面布置方案是停车场设计的核心工作。首先分析地块周边控制要素,提出了地面方案、高架方案及双层方案三种平面布置形式,并从运营组织、工程投资等方面综合对比,推荐采用双层方案,解决了停车场布置用地受限问题。同时针对双层方案联络线设置进行了进一步的讨论,以期为之后类似车辆基地平面布置提供参考。

中吉乌铁路线路宏观走向方案研究

以中吉乌铁路为研究对象,从沿线经济据点分布、吉尔吉斯斯坦国家铁路网衔接角度、沿线天山山脉的地质条件以及沿线分布的矿产资源情况出发,通过对线路宏观走向方案的系统研究及比选,提出了中吉乌铁路在宏观走向方案上的建议。

带有联络线的地铁换乘站设计要点分析——基于武汉11号线四期芳草路站建筑设计的思考

本文通过对武汉11号线四期芳草路站建筑设计的总结,分析了带有联络线的地铁换乘站设计要点。