架空和电缆混合馈线的线损估算

提出了架空和电缆混合馈线的线损估算方法。在分析架空线和电缆线功率损耗的基础上,先构造混合馈线线损估算的非线性回归模型。模型以混合馈线所含架空线长度、电缆线长度、馈线首端的有功和无功功率为独立变量,通过高阶多项式反映混合馈线的损耗随独立变量变化的复杂关系。针对非线性线损估算模型中的待求回归系数,基于Gauss-Raphson法推导了迭代求解公式;设计了相应的计算程序,并采用实测数据对所提模型和算法进行了仿真计算和分析,得到的检验回归模型合理性指标表明,给出的线损估算模型有效、可行,为架空和电缆混合馈线的线损估算可提供高效率的途径。     

Effect of overhead ground wires on reduction of failure rates of surge arresters on power distribution lines

Surge arresters are sometimes damaged by lightning strokes with high energy, in spite of installation of conventional protection methods. In order to reduce the number of failures of surge arresters, we should consider another protection method, such as an increase in the withstand capability of surge arresters and installation of additional overhead ground wires. However, quantitative comparison of these methods for preventing damage to surge arresters against lightning strokes with high energy has never been performed. This paper describes the effects of additional overhead ground wires for preventing damage to surge arresters. The main results are: (1) The failure rate of surge arresters on a distribution line with two overhead ground wires is about one third of that with an overhead ground wire. (2) Installation of a second overhead ground wire six to eight spans from the end of a line reduces the failure rate of a surge arrester at the end as effectively as increasing the withstand capability by a factor of two. © 1998 Scripta Technica. Electr Eng Jpn, 122(2): 12–20, 1998     

Manipulator system for constructing overhead distribution lines

A manipulator for live-line construction of high-voltage overhead power transmission lines (line voltage 6.6 kV) is described. This system's development concept, makeup, functions, and design, as well as operability tests using actual-scale transmission line poles, are described. Development began in 1984, and a prototype model of a ground-mounted twin-arm manipulator was trial-manufactured in 1985. In 1988, a truck-mounted system was developed in which the twin-arm manipulator was mounted on a cherrypicker vehicle. A practical system was developed based on these implementations     

架空绝缘配电线路施工时的接地问题

在日常施工管理中 ,部分单位在架空绝缘配电线路施工中存在不安全的情况。例如 ,架空绝缘配电线路停电施工时的接地问题。在全部或部分停电的电力线路上工作时 ,停电、验电、挂接地线是保证电力线路施工人员安全的三项重要技术措施。《电业安全工作规程》第4.3.1条规定 :线路经     

黑龙江省电网架空输电线路舞动分布研究

为预防由于线路舞动而造成跳闸问题,基于2000-2010年黑龙江省电网架空输电线路舞动次数、运行经验、地形地貌及气象等因素基础上,对黑龙江省电网架空输电线路舞动区域进行等级划分,并绘制舞动分布图,以保证线路安全运行.     

架空绝缘配电线路综合防雷措施的应用

按照“疏导”与“堵塞”相结合的配网综合防雷思路,开发了一系列产品,其中,保护型绝缘子可“疏导”雷电流,玻璃钢绝缘横担提高了耐雷水平,保护型间隙横担通过引导架空线路闪络位置并采用限流元件与长闪络距离的协同作用截断工频续流,试验与应用结果表明,能有效降低架空绝缘配网的雷击断线与跳闸的机率。     

Analysis of one-line ground fault surge on simulated overhead distribution line

One-line fault location techniques of intermittent ground fault points on nongrounded distribution lines are necessary to supply steady electric power for customers. This paper proposes a novel method that uses frequency spectra of transient waveforms at a sending end when an intermittent ground fault occurs. In this method, if a ground fault position differs, it causes a different frequency spectrum pattern for the current or voltage transients at a send end (decided by surge reflection phenomena between the sending end and the ground fault point). Comparison between experimental data of one-line ground fault tests on a simulated overhead line (373 m line length, two branch points) and digital simulation analyses shows that the grounded capacitance of a power source transformer was useful in locating the ground fault point. © 1997 Scripta Technica, Inc. Electr Eng Jpn, 118 (1): 52–60, 1997     

Current collection characteristics and improvement methods of high-tension overhead catenary systems

With increasing speeds on electric railways, overhead catenary systems on narrow-gauge lines have been improved by increasing messenger wire tension. However, the contact loss ratio of the pantograph is comparatively high in heavy-simple or feeder-messenger wire-type overhead catenary systems. These catenaries have higher tension of the messenger wire. In order to investigate the causes of contact loss and to work out effective improvement methods, laboratory and field tests have been carried out. From the results thereof, it is confirmed that the contact force fluctuation is influenced by the wave reflection factor at the hanger, and a hanger which has a spring mechanism is found to effectively improve it. It is expected that rubber damping hangers or friction damping hangers will reduce contact loss of the pantograph and wear of the contact wire. © 1998 Scripta Technica, Electr Eng Jpn, 123 (4): 67–76, 1998     

Detection of and protection for internal low-current winding faultsin overhead distribution transformers

Changing protection practices for overhead power distribution transformers involves mounting the arrester on the transformer tank and using lightning-surge-tolerant fuses to provide protection. Concerns about protecting transformers against low-magnitude internal winding faults as a result of this practice are addressed in this paper. An analysis of a high-power test involving primary and secondary winding faults is presented. The magnitude, duration, and “signature” of the winding faults are determined and categorized. An analysis of the response of surge-tolerant fuses shows that they often will not detect low-current winding faults before they propagate to the available system fault current. Testing also demonstrated the performance of current-limiters to effectively reduce the available system fault current, thereby minimizing stress to the transformer. The use of current limiters is recommended with surge-tolerant fuses. The pressure rise in the tank for primary winding faults is mainly caused by low-fault current and, when protected with current limiters, the relief device easily vents the gases. The pressure rise for secondary winding faults is more rapid and can exceed the capability of the relief device to limit the overpressure     

浅谈中压架空绝缘配电线路的防雷措施

随着城网改造的深入发展,绝缘导线被广泛应用于中压配电网,它有效降低了电能损耗,提高了供电的可靠性,然而因其特殊性所导致的防雷问题也随之而来。1导线雷灾特点1.1绝缘导线架空线路绝缘导线遭遇雷击时,几乎全部发生断线事故,原因是当雷击绝缘架空线路时,绝缘层被雷击闪络击穿,瞬时会产生数千安培工频续流流过针孔状击穿点,其电弧受周围绝缘的阻隔,电弧集中在击穿点燃烧导致导线烧断,绝缘线路导线断线多集中在绝缘导线固定处。1.2裸导线线路裸导线线路被雷击闪络后,工频续流电弧因电动力作用将向导线的负荷方向侧移动,并在工频电流烧断导线…     

架空配电线和电力屏蔽电缆的传输特性测量与分析

中压配电线是广泛存在的资源,利用中压配电线来实现数据通信对配电自动化及公用通信是最经济、最便捷和最有效的方式。为了评价中压配电线作为通信媒体的传输特性,文章对位于南京市郊的一条中压10 kV配电线路进行了现场测量,对100~450 kHz频率范围内的线路阻抗、噪声及传输衰耗特性进行了系统地分析研究,并且利用计算机对测量的大量数据进行了统计分析,给出了一些具有价值的结论,讨论了其对宽带数字载波通信的影响。     

城市10kV配网架空设备改造的技术探讨

分析了目前深圳城市10kV配网架空设备的状况,结合实际探讨了各类架空设备的整改方案以及相应的技术要求。     

EMTP modeling of a triggered-lightning strike to the phaseconductor of an overhead distribution line

A triggered-lightning experiment and EMTP modeling of that experiment are used to study the responses of a two-conductor overhead power line to a direct lightning strike. The experiment was conducted at the International Center for Lightning Research and Testing (ICLRT) at Camp Blanding, FL. The lightning was artificially initiated (triggered) from a natural thundercloud using the rocket-and-wire technique, and its current was directed to the phase conductor. EMTP modeling of the line behavior yields results that are generally consistent with the measurements     

城市架空线入地改造供电模式初探

根据近几年闵行地区电网已实施的架空线入地工程,针对不同地区的需要提出了不同的供电模式和解决方案,并总结不同的供电模式和解决方案的利弊。     

Modeling of electrostatic-based pesticide spray systems

A microscopic model for the electrostatic spraying system is presented to investigate the effect of the voltage applied to the induction nozzle on the droplet's charge, mobility, and charge-to-mass ratio. The variation of these parameters along the jet was also included. The model also lays particular emphasis on the effect of the applied voltage on the spray current and the charge density at the nozzle. A macroscopic model for the electrostatic spraying system is also presented. The objective of the model was to study the spatial distribution of the droplet charge density, transit time, and trajectory in the region between the nozzle and the target in terms of the flow velocity of the spray and the space-charge-produced electric field. On the macroscopic scale, both the droplet charge density and the spray current increase with the voltage applied to the charging electrode. With the decrease of the spray flow velocity, the space-charge-produced electric field becomes dominant and tends to: contract the droplet trajectories toward the axis of the spray system, and hence enhance the droplet deposition efficiency; and decrease the charge density at the target with the possibility of minimizing back-ionization. On the microscopic scale, induction charging eliminates the ion current from the current to the target and the associated back-ionization. The calculated droplet charge and charge-to-mass ratio which increase with the voltage applied to the charging electrode, agreed with the values reported previously     

Analysis of shunt faults in the laterals of overhead power distribution feeders using superimposed components

In this study, a digital fault location and monitoring technique for overhead power distribution lines with laterals is presented. The technique is based on utilising the fault voltage and current samples obtained at a single location. In the implementation of the algorithm, the superimposed voltage and current components rather than total values are used to minimise the effects of preloading on the accuracy. The effectiveness of the method is verified through electro-magnetic transients program simulations.     

10kV架空配电线路不停电作业的应用探讨

随着国民经济的快速发展和人民生活水平的大幅提高,用户对供电可靠性的要求也越来越高。特别是2008年中国南方电网公司提出“以提高供电可靠率为总抓手”的总体工作目标,更凸显出提高供电可靠性的重要性。不停电作业是今后配网线路作业的主要发展方向,是提高配电系统供电可靠率和电网稳定性的有效途径。实现10kV配电线路不停电作业的各种作业方式：带电作业,移动电源作业法和旁路作业法;分析各种作业方法的优缺点和使用范围。     

防止配网架空绝缘导线雷击断线和跳闸的措施

随着城市配电网络大量采用架空绝缘导线,虽然减少了线路因树线矛盾、外力破坏造成的故障,但同时也提高了雷击断线的几率.通过分析绝缘导线易雷击断线的机理,结合国内外防止雷击断线及雷击跳闸的技术措施,提出了在线路运行过程中应采取的对策及措施.减少配电网络的雷击跳闸次数.     

Modeling of transoceanic fiber-optic WDM communication systems

The rapid growth of long-haul wavelength-division multiplexing (WDM) fiber-optic telecommunications challenges lightwave system designers to increase the transmission capacity per fiber pair, while reducing the time to market. This makes it essential to have fast and accurate computer modeling tools to aid the systems design. There is a natural engineering tradeoff between simulation speed and accuracy; fast approximations tend to be inaccurate, while the exact treatment of the physical processes affecting transmission are nearly impossible to capture in a time-efficient algorithm. The proof of a successful tool development lies in the comparison of simulation results to transmission system measurements. In this paper, we discuss a new simulation technique based on careful evaluation of the key physical effects that produce system impairments. We show that this new approach can produce fast and accurate simulations of long-haul WDM transmission systems