Research on Distance Judgement Method from Point to Line to Generate a Line

Regarding the problem that the traditional straight-line generating has a low accuracy, we study straightline generating with the distance of point to line. We explore generating a line to approximate the ideal line and the issue is to pick out the pixel point of approximating the ideal line. The paper plays a significant scientific role in elucidating linear optimization norm and it lays a foundation for showing a straight line. The algorithm is valuable for computer graphics.

Safety Distance Determination for 500 kV AC Transmission Line’s Helicopter Inspection

As an efficient and advanced line inspection method, helicopter line patrol is gradually more and more used in transmission lines inspection, promoting the elaborate operation of transmission lines and reducing the management cost. However, as a 'floating-potential conductor' near to a high-voltage transmission line, the helicopter would be at a high electric field region;and bring security risk to equipment and operating personnel. In this paper, the electric field strength near the cabin at locations of different distance from transmission lines is investigated by calculation, and the field in the helicopter cabin is also calculated with finite element method (FEM). The result indicates that the potential difference becomes higher with the decrease of the distance between the helicopter and transmission line. Considering the discharge energy and the guarantee of the persons’ safety, the safety distance is determined as d≥15 m.

Calculation of the Two High Voltage Transmission Line Conductors’ Minimum Distance

In the design of high voltage transmission lines inevitably needed to change the arrangement of wires, and the distance between the wires directly affected by changing the arrangement of the wires. The distance between the wires is difficult to judge by experiences. Therefore, it is urgently to develop a way to accurately calculating the minimum distance between the wires when changing the arrangement between the two wires, and determine the minimum distance can meet the requirements of standards and regulations or not. Through the thinking, based on the balance equation and the space curve wire calculus method, a more accurate method of calculating the two wires in a variety of conditions the minimum spacing was derivated, and the sensitivity of the minimum distance was analysized based on the method.

Transmission Lines Distance Protection Using Differential Equation Algorithm and Hilbert-Huang Transform

This paper proposed the scheme of transmission lines distance protection based on differential equation algorithms (DEA) and Hilbert-Huang transform (HHT). The measured impedance based on EDA is affected by various factors, such as the distributed capacitance, the transient response characteristics of current transformer and voltage transformer, etc. In order to overcome this problem, the proposed scheme applies HHT to improve the apparent impedance estimated by DEA. Empirical mode decomposition (EMD) is used to decompose the data set from DEA into the intrinsic mode functions (IMF) and the residue. This residue has monotonic trend and is used to evaluate the impedance of faulty line. Simulation results show that the proposed scheme improves significantly the accuracy of the estimated impedance.

NEW METHOD OF CALCULATING SHORT CIRCUIT LONG DISTANCE EHV AC TRANSMISSION LINES

In this paper a practical but sufficiently accurate method of calculating transient components in short circuit currents and voltages is proposed. It enables to find the roots of the characteristic equation of high order without forming and solving it. This method is convenient to use especially in case of complicated expansionary power systems.

Safe Distance for Inspection of 1 000 kV UHVAC Lines with Helicopter

Helicopter inspection of ultra high voltage （UHV） transmission lines has unmatched advantages compared to manual work due to the inspection angle and high-tech equipment on board, especially in detailed inspections of tower heads and defect-detections in virtue of infrared/ultraviolet techniques. This paper deals with some key technical problems in the inspections of i 000 kV UHVAC lines with a helicopter, such as the safe distance of live-line working, electromagnetic field intensity and flight control. Based on the study results, a set of UHV line inspection methods was worked out and applied to the inspection of live UHV lines.

Application of a Space-based Optical Interferometer Toward Measuring Cosmological Distances of Quasars

Measuring quasar distance through joint analysis of spectroastrometry and reverberation mapping observations is a new method for driving the development of cosmology.In this paper,we carry out detailed simulation and analysis to study the effect of four basic observational parameters(baseline length,exposure time,equivalent diameter and spectral resolution)on the data quality of differential phase curves(DPCs),and furthermore on the accuracy of distance measurement.In our simulation,we adopt an axisymmetrical disk model of a broad line region(BLR)to generate differential phase signals.We find that the differential phases and their Poisson errors could be amplified by extending the baseline,while the influence of optical path difference errors can be reduced during fitting the BLR model.Longer exposure time or larger equivalent diameter helps reduce the absolute Poisson error.Therefore,the relative error of DPCs could be reduced by increasing any of the above three parameters,then the accuracy of distance measurement could be improved.In contrast,the uncertainty of absolute angular distances(D_(A))could be improved with higher spectral resolution,although the relative error of DPCs would be amplified.We show how the uncertainty of distance measurement varies with the relative error of DPCs.For our specific set of model parameters,without considering more complicated structures and kinematics of BLRs in our simulation,it is found that the relative error of DPCs<20%is a limit for accurate distance measurement.The relative error of DPCs has a lower limit(roughly 5%)and the uncertainty in distance measurement can be better than 2%.

用解析法求解“Philo’s Line”

从数学分析入手,运用极值原理,找到了“Philo’s Line”在给定条件下的解析表达式,由此解析表达式作出“Philo’s Line”图形.为在铁路、公路、桥梁等工程设计中,确定过定角内一定点并与角的两边相交,且夹在交点间的线段最短的直线,提供了切实可行的方法.

基于故障主动控制的海上风电交流汇集线路时域距离保护

海上风机通过电缆线路与海上模块化多电平换流器(MMC)相连接,构成海上风电交流汇集系统。由于海上风电交流汇集线路双端均为电力电子设备,基于双端通信的差动保护存在一定风险;其短路电流幅值受限、相位受控且具有大量谐波分量,基于工频量的距离保护可靠性较低。鉴于此,该文提出一种故障主动控制下计及分布电容影响的时域距离保护方案。首先,提出降压限流控制策略,以避免海上MMC换流器在严重故障下的误闭锁;其次,为放大海上换流器故障特征并解决双端故障电流的相位差异导致单端距离保护性能下降的问题,利用海上MMC换流器的故障主动控制能力,通过锁相环调制特定频率的负序故障分量,该特定频率分量仅存在于换流器与故障点之间,从而避免了风机故障电流的影响;再次,充分考虑电缆分布电容的影响,基于线路π型模型推导故障微分方程,结合最小二乘法求解故障距离,并构造保护判据;最后,基于PSCAD/EMTDC仿真平台验证了所提方案的可行性及有效性。

Research on Total Electric Field for DC Lines Converted from Double-Circuit AC Lines

With rapid growth of power demand, transmission capacity is also in urgent need of upgrading. In some cases, converting existing AC transmission lines to DC lines can Improve the transmission capacity and reduce the construction investment. In this paper, the upstream finite element method was expanded to calculate the total electric field of same tower multi-circuit DC lines converted from double-circuit AC lines, and the validity of the algorithm was confirmed by experiments. Taking a DC line converted from a typical same tower 500 kV double-circuit AC transmission line as an example, the surface electric field and the ground total electric field in different pole conductor arrangement schemes were calculated and analyzed, and the critical height of pole conductors for DC lines in residential and non-residential area were determined. Then, the corridor width of DC and AC lines at critical height in residential and non-residential areas before and after AC-DC line transformation were compared. The results indicate that for DC lines converted from common 500 kV double-circuit AC lines, the ground total electric field can meet the requirements of corresponding standard with appropriate pole conductor arrangement schemes.

The Four Intersection-and-Difference Model for Line-Line Topological Relations

The description of line-line topological relations is still an unsolved issue although much effort has been done. The problem is involved in many practical applications such as spatial query, spatial analysis and cartographic generalization. To develop a sound and effective approach to describe line-line relations, it is first necessary to define the topology of an individual line, i.e., local topology. The concept of connective degree is used for the identification of topological differences in the geometric structure of a line. The general topological definition of a line is given, i.e., endpoints set and interior point set. This definition can be applied to the embedded spaces of different dimensions, whether co-dimension is equal to or larger than zero. On this basis, a generic model called the 4 intersection-and-difference is set up for the description of basic line-line topological relations, upon which a conceptual neighborhood graph is built with consideration of topological distance, it is concluded that the proposed model can represent the property of topological changes, and basic relations between line segments in IR^1 and IR^2.

Comparative evaluation of maize inbred lines (zea mays l.) according to dus testing using morphological, physiological and molecular markers

A major challenge facing those involved in the testing of new plant varieties for Distinctness, Uniformity and Stability (DUS) is the need to compare them against all those of 'common knowledge'. A set of maize inbred lines was used to compare how morphological, physiological characterization and RAPD molecular marker described variety relationships. All the inbred lines were confirmed as morphologically and physiologically distinct. At morphological level the maximum genetic distance (10.8) and least genetic distance (1.6) were found. For physiological characters distance varied from 0.35 to 1.92 and results from dendrogram, which was made on the basis of dissimilarity matrix, were grouped into five major clusters. From RAPD, random primers provide polymorphic amplification products;the distance varying 0.42 to 0.65 and dendrogram showed that these lines formed close clusters due to the less variation in these lines at molecular level. In the present study, the molecular markers also exposed useful genetic diversity and the visual displays appeared to disperse the lines somewhat more evenly over the plot than the morphological and physiological methods.

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.

抑制分布式静止串联补偿器对线路保护影响的方法研究

分布式静止串联补偿器(distributed static series compensator,DSSC)通过调节注入线路的电压可改变线路功率,优化电网潮流分布。针对现有交流线路保护算法难以适应DSSC串入线路运行的问题,提出了抑制DSSC对线路保护影响的方法。首先,分析了DSSC对交流线路保护的影响,证明了DSSC注入电压可能改变距离保护的阻抗测量值,导致距离保护有拒动或误动的风险。然后,提出了利用DSSC本体过流保护快速将DSSC旁路、或基于故障辅助判据主动将DSSC注入电压降为0的方法,以抑制不同类型的线路故障时DSSC对线路保护的影响。最后,基于硬件在环RTDS实时仿真平台以及浙江湖州DSSC示范工程现场进行试验,验证了所提抑制DSSC对交流线路保护影响的方法的有效性。

Impact of Sensor Technology for Line Protection Performance

The paper has presented the impact on the line protection performance with the introduction of MUs （merging units） in the process bus level. The paper begins with the introduction on modem digital substation structure and process bus. Then, the paper describes the performances of different sensors such as CTs （current transformers）, CVTs （capacitive voltage transformers）, FOCS （fiber optical current transducers） and FOVS （fiber optical voltage transducers）. With the use of above transducers together with MUs, the performance of distance protection function and line differential protection function have been investigated and presented. Finally, conclusions based on the study are presented in the paper.

强风作用下输电线路的脱冰响应研究

在强风作用下,输电线路的脱冰过程会产生冲击效应并缩短相间距离,极大增加了电气事故发生的可能性。该文基于新疆某线路局部区段的实际参数,建立强风作用下“导线-绝缘子”的脱冰响应有限元模型,分析了在不同风速、风攻角条件下输电线路脱冰档最大弧垂处的位移、不平衡动张力和各相间的最小距离。结果表明:风攻角对异形覆冰导线的气动系数与风载增大系数存在明显影响;在强风条件下的动张力幅值具有超过设计抗拉强度的情况,存在断线的可能;强风作用下输电线路的脱冰过程相较其初始构型位置是一种向上偏斜的位移过程,存在相间距离显著减小情况,运行时放电风险的概率远远超过无风脱冰工况。该文针对强风作用的输电线路进行研究,探究了复杂工况下的脱冰响应特征和运行时的放电风险,为输电线路在强风天气下进行紧急防冰、除冰技术提供一定的参考。

800 km客运班线事故特征及情景研究

为降低800 km以上客运班线事故潜在发生性,提高企业安全防控能力,研究分析了800 km以上客运班线事故典型特征,构建事故发生重要情景。基于2014—2020年800 km以上客运班线道路交通事故数据展开致因分析及事故易发情景研究。以人、路、环境为依据,选取关键特征构建了事故特征指标体系。利用决策树模型构建了安全风险模型,探索了运行时段、人因、天气状况、季度、事故发生地区、道路线形、路面状况、节假日情况、春运情况、公路技术等级和公路行政等系统关键因子与翻车、刮擦、碰撞、撞击固定物、追尾、坠车等事故形态间的潜在关系。剖析了事故发生时交通系统内人、路及环境等因素特征及形态,以此构建了800 km以上客运班线的事故易发情景。结果表明:运行时段、人因、天气状况是影响800 km以上客运班线事故发生的关键因子,且与季度、事故发生地区、道路线形、路面状况等因子存在多重耦合关系;节假日情况、春运情况、公路技术等级和公路行政等级不是影响800 km以上客运班线事故发生的关键因子。研究为降低800 km以上客运班线的事故潜在发生性及企业安全防控提供理论依据。未来,道路运输管理部门与道路运输企业应强化安全管理,规范驾驶员安全驾驶行为,普及事故易发情景下的防御性驾驶知识。

智能汽车内外饰造型意象耦合度评价方法研究

为帮助设计人员在智能汽车造型设计早期更好地控制内外饰传达的整体意象,提出一种基于眼动实验,结合感性工学理论的智能汽车内外饰造型意象耦合度评价方法。以耦合理论为核心,通过调研获取感性意象词汇集和内外饰并存图库,引入观察距离作为调剂因子统一内外饰意象评价,运用语义差分法构建内外饰总体意象空间并获取意象过渡线;运用眼动实验获取车内外关键设计要素及客观认知权重,经专家评审修正后计算其综合权重并与意象评分结合,探索基于意象认知耦合的智能汽车内外饰造型耦合度评价方法。该方法以3款智能汽车为评价对象,将评价结果与语义差分所得评分进行对比验证,结果表明该方法准确性良好,可以指导后续智能汽车内外饰造型耦合设计。

基于SVM的富水岩溶区双线盾构隧道下穿既有线临界安全距离研究

双线盾构隧道在极复杂的岩溶地质中下穿既有线施工时,会对地层造成较大扰动,从而增加既有地表沉降过大或坍塌的风险,严重威胁既有线的运营安全。同时,隧道穿越富水岩溶区域时,需要保持一定距离以避免与溶洞相交,确保双线盾构隧道围岩的稳定性。利用FlAC^(3D)软件建立不同工况组合下双线盾构隧道与左侧溶洞的临界安全距离数值模型,分析不同地下水位对既有线沉降和围岩塑性区范围的影响,并采用正交试验和多元线性回归方法建立双线盾构隧道在不同围岩等级、地下水埋深、开挖隧道埋深和溶洞孔径组合下与溶洞的临界安全距离计算公式。此外,还基于SVM模型对正交试验结果进行机器学习,得到可以预测岩溶地区双线盾构隧道临界安全距离的智能预测系统,实现双线盾构隧道下穿既有线临界安全距离的非线性智能预测。结果表明:当地下水位位于既有线以上时,其水位越高,既有线的沉降量越大、围岩塑性区范围越大,地下水对盾构隧道与溶洞的临界安全距离有很大影响,应用SVM模型和多元线性回归方法确定双线盾构隧道与溶洞之间的临界安全距离是行之有效的。