天津独流减河工程监控系统现地通信单元设计

提出一种配电网电容电流测量的新方法，在零序电压互感器的开口三角侧串联一个可调电感，通过注入一个变频恒流信号寻找配电网的谐振频率，改变可调电感的数值后寻找另一谐振频率，联立2个谐振方程求解电容电流，该方法消除了电压互感器漏抗对测量的影响。开发了配电网电容电流测量仪，经模拟试验和现场测试表明，该方法具有安全、快捷、准确等特点，适用于中性点不接地或经随调式消弧线圈接地配电网。     

调匝式消弧线圈自动调谐新方法

对调匝式消弧线圈的自动调谐，提出了利用谐振法结合曲线拟合法测量电容电流的新方法：找出谐振点左右的3点，代入拟合曲线方程，求出谐振点的感抗值（等于系统容抗），由此求出电容电流。该方法具有状态识别功能，能区分线路投切状态和调谐状态，无需相互通信便可实现变电站内部和变电站之间的多台消弧线圈的自动并联。模拟电网试验和现场运行试验结果令人满意。     

浅谈10kV电网中性点经小电阻接地自动跟踪补偿消弧装置

随着电网、经济的发展，变电站10kV出线中，电缆所占比重越来越高，导致10kV系统的电容电流越来越大，远远超过了规程规定的10A（10kV为架空线和电缆线混合的系统）。因此，需要在10kV电网中采用中性点谐振接地（经消弧线圈接地）方式。理想的消弧线圈能实时监测电网电容电流的大小，在正常运行时电抗值很大，相当于中性点不接地系统，在发生单相接地故障时能在极短时间内自动调节电抗值完全补偿电容电流，使接地点残流的基波无功分量为零。小电阻接地自动跟踪补偿消弧装置基本上能实现上述功能，能将接地故障电流限制在允许范围内，保证电力系统的可靠运行、人身及设备的安全。图1幅。     

谐振接地系统的新型自动调谐装置

分析了线路对地电容对故障电流负序分量和零序分量的影响以及故障电流负序分量在配电系统中的分布特征，提出了根据接地时刻线路负序电流的相对最大值确定故障线路、根据故障线路负序电流和消弧线圈电流的相位差决定消弧线圈的调节方向、以故障线路负序电流分量的最小值为调节目标的新型综合自动调谐方法。该调谐方法在完成调谐的同时也完成了故障选线，但它并不以正确的故障选线为前提条件，无须测量配电系统的对地电容，也不受配电系统运行方式的影响。即使在故障接地期间改变配电系统的运行方式，该方法也能及时判断并准确调节消弧线圈电感使配电系统重新回到谐振状态。对开发的新型自动调谐装置样机进行了动模实验，结果验证了所提出的方法的正确性和装置的可行性。     

消弧线圈在中压电网中的应用分析

随着电网的发展，大量电缆应用到配电网中，当系统发生单相接地故障时，电容电流变大，威胁到电网的安全、稳定运行。文章分析了电容电流的产生和危害及消弧线圈在非有效接地系统中应用的必要性；阐述了消弧线圈的工作原理、容量选择等相关问题；对各类型消弧线圈的优缺点进行了分析。     

基于对称法与相位法的新型消弧线圈

分析了当前自动跟踪补偿消弧线圈技术的发展以及存在的问题，提出了基于对称法与相位法相结合的新型消弧线圈设计方案，介绍了电容电流检测方法和装置结构。该方法利用了零序电压U₀与脱谐度υ关系曲线的对称性以及零序电压与线电压的相位关系，无需反复调节消弧线圈电感值就可快速、精确地跟踪测量电网电容电流。根据该方法研制出的新型消弧线圈试验和现场运行均表明，该型消弧线圈具有响应速度快、补偿精度高、无机械动作可靠性高等特点。     

自动跟踪补偿消弧装置在电力系统的应用

电力系统10～35kV系统多采用中性点不直接接地方式。随着城市电网建设规模的迅速发展，变电站的电力电缆出线越来越多，导致电网单相接地电容电流不断增大。系统发生单相接地故障时，电容电流大，接地点电弧不易熄灭产生弧光过电压，引发电力系统事故。中性点经消弧线圈接地，补偿了接地电容电流，限制弧光接地过电压，保证电网供电可靠性和电网的安全。采用自动跟踪补偿后，能实时适应负荷线路接地的变化实现高精度、快速可靠的自动调节。     

经消弧线圈接地配电网自动化改造的问题探讨

文章介绍了现有的消弧线圈自动调整及故障选线的方法；探讨基于注入信号法进行消弧线圈调谐的方法；改变消弧线圈档位，测量零序电流变化、进行故障选线的方法；以及采用ＧＰＳ行波进行故障定位的方法；最后提出了基于消弧线圈接地电网的自动化改造方案。     

配电网谐振状态与单相接地状态的辨识

谐振过电压一直困扰消弧线圈的自动调整及故障选线的正确动作。文中提出了谐振过电压的辨识问题，采用 注入信号跟踪的方法进行状态辨识。谐振时，调整消弧线圈挡位，消除谐振；接地故障时，进行故障选线， 切除故障线路。研制出新型的消弧线圈自动调整及故障选线综合测控仪，经实验室模拟试验效果良好。     

中性点非有效接地系统消弧装置试验研究

中性点非有效接地系统在电网中规模越来越大,当系统发生单相弧光接地故障时,由于电容电流过大而无法自行熄弧,因此会危及到电网设备的安全运行。针对宁夏电网中性点非有效接地系统消弧装置,对其运行状况、系统的电容电流、消弧装置的补偿电流以及残流进行了分析。分析结果表明:当电网出现单相接地故障时,消弧线圈由于存在本体电容电流测量不准、阻性分量、谐波分量等因素造成接地点的电流较大无法熄弧,而配置快速开关型消弧柜变电站则可以在20 ms内将故障点电流全部转移至变电站内的消弧柜,从而实现故障点彻底消弧。     

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。     

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。     

Desiccation and recolonization of phytobenthos in a regulated desert river: Colorado River at Lees Ferry,Arizona, USA

We tested the recolonization of the phytobenthic community in the tailwaters of Glen Canyon Dam following long- and short-term experimentally induced desiccation. The response of Cladophora glomerata, Oscillatoria spp., miscellaneous phytobenthos species and periphyton was studied over 18 weeks using three treatments: (1) undisturbed control cobbles from the submerged zone; (2) cobbles desiccated and replaced into the submerged zone; and (3) cobbles desiccated and replaced into the varial zone. Periphyton density and compositional response resulting from these treatments were also examined. Desiccation treatments were significantly different in biomass from controls throughout the study. The biomass of desiccated and replaced river cobbles averaged <30% of the controls for C. glomerata and periphyton during the 18-week recolonization period. In contrast, the biomass of the control Oscillatoria and miscellaneous phytobenthos species averaged only 3 and 50% of that in the desiccation treatments, respectively. Cladophora, the dominant alga, comprised 77% of the phytobenthic biomass. A significant positive relationship between discharge, Cladophora and periphyton biomass was present in all treatments, while there was a negative relationship with discharge for Oscillatoria and miscellaneous phytobenthos species. There was a significant inverse correlation, as well as a pattern of separate biomass dominance, between C. glomerata and Oscillatoria. Cladophora was the dominant phytobenthos species on cobbles below the baseflow and Oscillatoria was dominant on cobbles in the varial zone. In general, the Cladophora biomass decreased under intermittent drying conditions, while Oscillatoria declined under permanently wet conditions. Diatom composition was not significantly different between treatments; however, their density was lower on desiccated cobbles. Diatom density on desiccated cobbles in the submerged and varial zones averaged 69 and 42% of that of the controls, respectively. Recovery and maintenance of benthic resources are hindered by fluctuating flow regimes driven by electricity and irrigation requirements. Repeated desiccation of the phytobenthos has major effects on the bottom-up interactions in the Colorado River ecosystem. © 1998 John Wiley & Sons, Ltd.