新型混合式限流断路器设计及其可靠性分析

混合式限流断路器兼备了机械开关良好的静态特性和固态开关无弧快速分断的动态特性,是国际上断路器研究的新方向。文中提出了一种基于快速晶闸管的新型混合式限流断路器结构,并针对低压场合,开展了2 kA/320 V混合式限流断路器样机的设计研制工作。深入分析了限流断路器的关断可靠性,证明了关键参数设计的正确性,并对参数设计进行了优化。试验结果表明,自行研制的超高速斥力开关能够在接到分闸指令280μs时间内完成触头分离,将电流转移到由大功率快速晶闸管组成的固态开关电路上,该快速晶闸管开关电路可在最短53μs时间内实现对 10 kA短路电流的可靠分断。     

基于IGBT软关断的混合式限流断路器结构与分析

回顾了混合式限流断路器的发展，针对4 000 A/400 V低压场合，提出了一种新型的基于绝缘栅双极晶体管(IGBT）软关断技术的混合式限流断路器的结构，在保证能迅速切断故障的同时兼顾了IGBT的瞬间特性，这种结构具有简单、实用的特点。文中介绍了其工作原理及设计要点，并进行了相关的仿真实验，在此基础上分析了混合式限流断路器的性能参数。实验表明，它综合了机械式断路器和固态开关的优点，可以在故障发生后极短时间内达到限制短路电流增大的目的，将在电力系统中得到更广泛的应用。     

500 kV变电所35 kV母线短路电流限制措施

针对500 kV玉林变电所增容扩建工程中出现的1号主变压器35 kV 侧短路电流水平超过40 kA,通过采取对新增的2号主变压器选用高阻抗变压器,1号主变压器35 kV侧总断路器回路串接限流电抗器的措施,将1、2号主变压器 35 kV侧短路电流水平均限制在40 kA以内.     

500kV变电所35kV母线短路电流限制措施

针对500kV玉林变电所增容扩建工程出现的1号主变压器35kV侧短路电流水平超过40kA，通过采取对新增的2号主变压器选用高阻抗变压器，1号主变压器35lkV侧总断路器回路串接限流电抗器的措施。将1、2号主变压器35kV侧短路电流水平均限制在40kA以内。     

超导限流储能系统的集成设计与试验

为了试验超导限流储能系统（SFCL-MES）的基本原理，设计了1台220 V/25 A/6 kW的SFCL-MES模型样机。提出了一种用于配电系统的SFCL-MES的系统结构，它由2个串联于变电站负荷的故障限流端口及1个并联于变电站母线的储能端口组成，既可以限制变电站的短路电流，又可以提高整个变电站的供电质量。分析了SFCL-MES的集成设计原理，讨论了SFCL-MES的4个组成部分：双向换流器单元、双向电流调节器单元、全波整流桥单元以及高温超导磁体单元的设计结构以及主要参数。在模型上对SFCL-MES的故障限流原理进行了试验，初步验证了它的有效性。     

断路器电磁操作机构辅助开关接点的调整

断路器电磁操作机构辅助开关的合闸常闭接点通电时间,应满足断路器动触头在合闸运动过程同静触头之间的金属短接时间,保证断路器的动触头完全达到合闸位置,才能切断操作电流。为此,需借助示波器类的测量仪器来进行电磁式操作机构操作电流动作全过程的测量,才能进行准确的调整。     

水电站典型厂用变支路接线及继电保护配置分析

对水电站3种比较典型的厂用变支路接线进行分析,讨论在厂用变支路分别采用真空发电机断路器、限流熔断器和负荷开关组合以及离相封闭母线直接连接的情况下,厂用变支路的保护用电流互感器参数选择和继电保护配置的解决方案。     

带串联补偿故障限流器的仿真和实验

采用短路电流限制器（FCL）快速限制短路电流是提高系统稳定性和断路器开断能力的有效方法之一。文中研究了一种具有串联补偿作用的FCL模型——由补偿电容和旁路电感并联后与限流电感串联而成。正常情况下，由电容和限流电感对线路进行串联补偿；发生故障时，根据短路电流的大小控制门极可关断晶闸管的导通角，改变投入的限流电抗，达到限流目的。用MATLAB对馈线短路的仿真及采用单片机控制方案的单相实验结果表明，该限流器限流效果良好。     

大容量高速限流开关装置及其应用

大容量高速限流开关装置通过DSP和DDS等技术开断和限制短路电流,具有开断电流大,限流时间快和截流时间短的特点,可有效对电气设备进行保护,避免了巨大短路电流对电气设备的灾难性冲击,避免了因主设备烧毁而引发的大面积停电事故,可满足现代电力系统发展的需求。     

HE系列SF6发电机断路器的应用

HE断路器应用自能灭弧原理和外接并联电容器降低恢复电压上升速率,电流开断原理及结构新颖简单,额定开断电流达110kA,具有体积小、重量轻、独立的三相单元结构等多项优点,提高了运行水平,优化了电站厂房设备布置,特别适合于现有系统的改造。葛洲坝和丹江口水利枢纽是国内最早使用HE断路器的电站,通过应用,为国内开关行业和电力部门积累了值得借鉴的经验。     

地下厂房施工过程的三维非线性数值模拟分析

根据冗各电站地下厂房开挖支护的施工顺序,以隐式杆单元模拟锚杆,以壳单元模拟混凝土喷层,采用三维非线性有限元技术,对洞室群的开挖支护动态过程进行了模拟计算。通过三维非线性有限元计算分析得到:洞室群动态开挖过程中围岩应力变形的分布规律,围岩塑性区的发展规律,锚杆受力变化情况。计算结果表明:整个开挖过程中,洞周围岩位移变化规律正常,量值较小,塑性区主要分布在洞室周边,围岩稳定性较好;但在洞室交叉口处围岩的变形较大,出现较大范围的塑性区,在此基础上提出了支护措施优化方案,并对优化方案的效果进行了评价。     

Evaluation of freshwater mussel relocation as a conservation and management strategy

The relocation of unionacean mussels is commonly used as a conservation and management tool in large rivers and streams. Relocation has been used to recolonize areas where mussel populations have been eliminated by prior pollution events, to remove mussels from construction zones and to re-establish populations of endangered species. More recently, relocation has been used to protect native freshwater mussels from colonization by the exotic zebra mussel Dreissena polymorpha. We conducted a literature review of mussel relocations and evaluated their relative success as a conservation and management strategy. We found that 43% of all relocations were conducted because of construction projects that were forced to comply with the Endangered Species Act 1973 and that only 16% were monitored for five or more consecutive years. Most (43%) relocation projects were conducted from July to September, presumably a period when reproductive stress is relatively low for most species and the metabolic rate is sufficient for reburrowing in the substrate. The mortality of relocated mussels was unreported in 27% of projects; reported mortality varied widely among projects and species and was difficult to assess. The mean mortality of relocated mussels was 49% based on an average recovery rate of 43%. There is little guidance on the methods for relocation or for monitoring the subsequent long-term status of relocated mussels. Based on this evaluation, research is needed to develop criteria for selecting a suitable relocation site and to establish appropriate methods and guidelines for conducting relocation projects.     

基于模型试验的河床砂砾石层基本特性研究

为了经济可靠地确定深厚覆盖层的基本特性参数,以大渡河双江口水电站坝基河床砂砾石层基本特性研究为工程背景,进行大尺寸模型试验,研究河床砂砾石层的旁压模量和动探击数随密度、级配以及上覆压力的变化规律。根据室内模型试验结果,结合现场旁压试验及钻孔试验成果,推断出坝址区河床砂砾石相关层位的密度,并依此进行砂砾石室内力学试验,获得设计所需力学参数。研究成果可为深厚覆盖层基本特性测试提供新的方法。     

Serial discontinuities in a Rocky mountain river. I. Distribution and abundance of plecoptera

Samples were taken year-round at eleven sites along the altitudinal profile (2900-1400 m a.s.l.) of the Gunnison River, a 329 km tributary of the Colorado River, to document the distribution of the Plecoptera and to evaluate responses to hypolimnial-release dams in the headwaters and middle reaches. Twenty-two species were present, with the greatest species richness occurring in an unregulated segment upstream of the middle reach dams; average nymphal biomass over the study period (175 organisms, 395 mg dry mass m^?2) was also greatest in this segment. Only four species (58 organisms, 48 mg m^?2) were present in the tailwaters of the headwater dam and values were greatly reduced (nine species; 35 organisms, 180 mg m^?2) below the middle reach dams. The stonefly community recovered ca. 80 km downstream from the last dam (15 species; 244 organisms, 250 mg m^?2), apparently in response to natural resetting of environmental conditions corresponding to those above the middle reach dams. At the most downstream site (11) only four species (four organisms, 16 mg m^?2) were present. The observed distributional pattern is a classic serial discontinuity in response to hypolimnial stream regulation in a temperate latitude river.     

基于BP神经网络-马尔科夫链模型的隧道围岩位移预测

在隧道工程施工中,围岩位移预测起着很重要的作用。将BP神经网络-马尔科夫链模型引入到隧道围岩位移预测中来,通过对训练样本的学习,利用BP神经网络实现了对位移时间序列的滚动预测,同时得到了实测值与预测值的相对误差;在此基础上利用马尔科夫链对相对误差进行修正,有效地提高了预测结果的精度。并将该模型应用于某公路隧道拱顶下沉位移时序预测中,结果表明该模型具有精度高、科学可靠的特点,为隧道围岩变形的预测提供了新的途径。     

Short communication. Pipelines as a refuge for freshwater snails

In the lower River Murray, Australia, populations of gastropods have declined markedly over the past 40 years. Of the native fauna of about 18 species, only the ancylid Ferrissia petterdi remains common (but in patches), and another five species feature in sporadic local resurgences. Until recently the viviparid Notopala was thought to be extinct. The introduced physid Physa acuta is widespread, but in low numbers. The decline probably is associated with flow regulation, high turbidity and the introduction of common carp. Snail populations have persisted, however, in irrigation pipelines fed from the river, where they periodically cause blockages. This paper reports the discovery of the only known populaion of Notopala hanleyi in a pipeline where the inner wall accumulates microbial and other organic matter, providing high quality food for snails. In the Murray before regulation most of the periphytic biomass was probably microbial, as fluctuating water levels would have maintained littoral communities in a highly productive, early state of succession his postulated that, by stabilizing seasonal water levels, regulation has promoted the production of filamentous green algae, an inferior food source, and so displaced snail populations from the open aquatic environment.     

浙江省水域调查录入系统的设计和应用

浙江省水域调查录入系统将调查数据与电子地图相整合,对分类水域数据进行统计计算,并对输入数据进行合理性和完整性检查,得到调查范围内现有水域的详细数据,实现了水域调查数据输入、计算、统计和查询的数字化管理,提高了工作效率和工作质量,为各地下阶段水域保护规划编制和水域管理工作提供了数据支持。对该系统的设计原则、功能和技术设计等作了介绍。     

Automated system for removal and pneumatic transport of fly ash from electric precipitator hoppers

A system for removal and pneumatic transport of fly ash is examined, in which air pulses act on batches (pistons) of ash formed in a duct. Studies are made of the effect of several physical parameters on the force required to displace a piston of ash and these serve as a basis for choosing a system for removal and pneumatic transport of ash simultaneously from several hoppers of an electric precipitator. This makes it possible to separate the ash particles according to size without introducing additional components. Formulas are given for calculating the structural and dynamic parameters of this system and measurements of indirect dynamic parameters are used to calculate the input-output characteristics of the system. In order to optimize the system, configurations for summing several ducts into a single transport duct for pneumatic ash transport are proposed. Some variants of dry ash utilization and the advantages of producing of size-separated particles are considered. __________ Translated from élektricheskie Stantsii, No. 2, pp. 26–30 (2008).     

The flood pulse advantage and the restoration of river-floodplain systems

The ‘flood pulse advantage’ is the amount by which fish yield per unit mean water area is increased by a natural, predictable flood pulse. Evidence for this increase is presented from tropical and temperate fisheries. It is argued that increasing multispecies fish yield by restoring the natural hydrological regime is consistent with increasing production of other trophic levels and with restoration from ecological and aesthetic viewpoints. When applied to a river-floodplain system, this restoration would provide a large, self-sustaining potential for recreation, commercial exploitation, and flood control. An interim ‘natural flood pulse’ restoration approach is proposed for systems modified for navigation. This approach approximates the natural hydrological regime in a river reach and is intended as a first step in the long process of restoring the watershed.     

基于CT-连续加荷水泥乳化沥青混凝土细观损伤规律研究

利用CT技术对水泥乳化沥青混凝土的细观损伤过程进行实时扫描观测,获得了混凝土试件在连续加荷下的CT图像。通过采用直观分析法、CT数分析法、CT数与损伤变量关系3种方法分析表明,水泥乳化沥青混凝土的破坏过程可分为压密、扩容、裂纹扩展、破坏4个阶段,同时混凝土在受压过程中具有韧性,在极限荷载之前各断面处于压密和微扩容的强化阶段,极限荷载之后混凝土从损伤到破坏发展比较平稳。