直接并网的中小型发电机定子接地保护

指出了现有中小型发电机定子接地保护原理的不足。详细阐述了在发电机中性点不接地和经消弧线圈接地2种情况下，分别在系统侧单相接地和定子接地时机端零序电流和零序电压的方向关系。提出了基于零序电流与零序电压方向关系以及基于零序差流与零序电压方向关系的新型的定子接地保护原理。通过试验和现场运行情况表明了该保护原理的可行性。     

长洲水利枢纽发电机选择性定子接地保护设计

介绍了长洲水利枢纽发电机选择性定子接地保护方案设计及试验情况,该保护方案由零序方向元件和中性点零序电压元件共同构成,采用中性点零序电压元件作为动作判据,零序方向元件作为开放辅助判据,现场模拟试验结果证明了该方案的成功.     

基于相角差的发电机定子接地保护方向元件

分析了发电机发生内外部单相接地故障后,机端和中性点侧3次谐波电压、基波零序电压和零序电流之间相角的变化关系。在此基础上,提出基于相角判别的新型发电机定子接地保护方向元件。该方向元件由2部分组成:对距中性点50%以内的定子绕组故障,利用机端和中性点两侧故障分量3次谐波电压的相角值相等且为负值的特点构成;对50%以上范围的定子绕组故障,由于零序故障电压和电流均相对较大,采用零序电压和零序电流相位的关系来识别故障方向。该方向元件构成原理简单,可以与目前现场应用的各种单相接地保护方案配合使用,具有较强的工程应用前景。     

发电机定子接地零序功率方向保护

介绍了利用零序电流与零序电压间的相角差来判断发电机接地故障是发生在区内还是区外的方法.关健词: 定子接地; 零序功率方向; 保护     

大型水轮发电机定子绕组接地故障的数字仿真

根据大型水轮发电机定子绕组的结构，建立了新的接地故障时零序电压的数字仿真模型，探讨了水轮发电机发生定子接地故障后机端和中性点侧零序电压的变化规律。在此基础上，提出了一种简化的数字仿真模型，该模型可被用来分析各种定子接地故障保护方案的特性。     

大型发电机定子接地保护灵敏度分析与整定计算

对大型发电机定子接地保护灵敏度进行了分析，提出了两段式发电机基波零序电压定子接地保护的概念:低定值动作发信号，高定值动作跳闸停机。并阐述了大型发电机定子接地保护的整定及各定子接地保护整定值的配合关系。通过发电机定子接地保护之间的相互配合，在整个发电机定子绕组范围内发生单相接地故障时，发电机定子接地保护均能灵敏地动作。     

大型水轮发电机组保护若干技术问题探讨

针对水轮发电机组保护的若干实际应用问题进行了探讨,包括厂用变压器(以下简称厂变)高压侧电流是否差入主变压器(以下简称主变)差动保护、失磁保护阻抗圆选择、转子接地保护的实现方式、注入式定子接地保护启动失灵问题、发电机复压过流保护跳母联断路器问题、接地变短路阻抗对基波零序电压定子接地保护的影响等。针对上述问题给出了具体的建议:厂变高压侧电流不计入主变差动电流计算的前提是厂变低压侧母线上发生短路故障时,该电流产生的差流不会导致主变差动保护误动;水轮发电机失磁保护宜选择静稳阻抗圆;转子接地保护宜就地安装;注入式定子接地保护动作后,动作接点不会快速返回,启动断路器失灵时可靠性有所降低;发电机复压过流保护不宜动作于跳母联断路器;应校核接地变短路阻抗对基波零序电压定子接地保护的影响。     

自适应20 Hz电源注入式定子接地保护

为了弥补定子接地100%保护的不足，引入了20 Hz电源注入式保护方案。传统的20 Hz电源注入式定子接地保护的动作方程的接地阻值整定值是固定的，经整定后它在保护装置运行时就不会发生变化。文中论述了这一传统的保护方案的不足，提出了新的自适应式保护方案。新方案能随发电机运行工况、故障时接地位置的不同以及定子接地电流所允许限值的大小，自适应地调整接地阻值整定值大小，无需人为整定，从而能保证在任何故障接地位置，只要接地点故障电流大于允许安全电流，新方案都能快速动作，提高了发电机的安全运行，拓宽了20 Hz电源注入式保护方案的灵活性，具有很高的理论和工程应用价值。     

故障分量发电机定子单相接地保护应用研究

简要分析了发电机发生定子单相接地故障后，机端和中性点侧零序电压变化的特性,并对基波和3次谐波电压原理的发电机定子接地保护方案的灵敏度进行比较。研究表明，发电机绕组中部接地时电压增量相对较小，不利于保护灵敏度的提高。在此基础上，提出改进的利用基波和3次谐波零序电压综合信息量的差动保护判据。该判据忽略基波零序电压增量的影响，减少了调试和整定环节，能有效提高保护灵敏度。理论分析以及实验研究均表明其优越性。     

飞来峡电厂发电机定子接地保护的设计及应用

发电机中性点设备配置及定子接地保护设计不合理,区外接地故障时引起发电机定子接地零序功率保护误动作。文章从发电机中性点设备配置和定子接地保护的设计应用进行论述。     

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。     

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。     

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.     

浅谈天湖水电站水轮机运行故障及处理措施

简述天湖水电站投运以来各种故障的表现形式，分析其原因，提出了相应的处理方法及措施，并对合理利用国内外设备提出建议。