广西鱼梁电厂1~#机组起励建压失败原因分析

分析广西鱼梁电厂1#机组起励建压失败的故障原因,介绍故障排除过程及处理措施,并对故障处理经验进行总结介绍。     

一起水轮发电机组励磁系统建压失败事件的分析及处理

简述了天生桥一级水力发电厂励磁系统改造后的基本情况和起励方式,介绍了2号机组首次零起升压过程中起励建压失败事件的全部情况及排查过程,并分析事件的原因及解决办法,最后对该事件的发生进行了总结并提出建议.     

发电机起励失败的原因分析及处理

自并励接线方式的发电机起励困难是其缺点之一,通过典型案例分析其起励失败的原因,并提出解决自并励发电机的起励有效办法,就是自并励发电机必须有他励建压功能,确保发电机在新投产或大修后等不同条件下均能可靠建压。     

无厂用电源时机组起励问题的分析

本文分析了安康水电厂无厂用电源时机组不能起励建压的原因，介绍了解决这一问题的两种方法。     

小型水电站的自动起励控制电路

发电机剩磁感应的残压,折算到励磁整流变压器副边的电压值很小,难以建立发电机端电压,故水轮发电机的励磁调节器是采用蓄电池或交流整流两种起励方式。蓄电池起励方式,每次开机发电都要进行电池充磁,激磁起励建压;交流整流起励方式,一旦发电机组停     

电压频率对复压记忆过流保护的影响分析

针对小容量自并励机组在系统远方故障甩负荷时复压记忆过流保护的动作情况,分析了电压频率变化对复压记忆过流保护的影响,介绍了采样点修正法和电压跟踪式过流保护原理,提出了相应的解决方案。     

发电机建不起压的特殊故障及处理

某电站3台320kW机组均采用可控硅静止励磁装置,在多年的运行中曾遇到各种故障,但发变单元回路故障引起不能建压的现象却少见。这类故障在出现时若不认真观察各种现象,很难正确判断故障原因,不利排除故障。 故障现象一:按起励按钮,灭磁开关动作灭磁,机组自动关机。检修人员判断为励磁装置故障,但经对装置各回路检查,均未发现异常。再次开机起励建压,又出现同样     

老挝南湃水电站机组起励失败原因分析与探讨

简述老挝南湃水电站励磁系统的基本组成和起励方式,分析电站1号机组检修后起励失败的原因,介绍故障排除过程及处理结果,并对现场励磁系统的原理、起励方式等进行探讨和总结,对同类型电站励磁系统的故障查找及解决有借鉴作用。根据三相交流发电机的基本原理,阐明了本站2台发电机电枢绕组直流电极性相反均能正常发电的原因,其剩磁极性由机组调试阶段使用直流焊机充磁决定。介绍了本站励磁系统励接线方式的优点和缺点,并针对接线方式的缺点采取相关措施。     

小型同步发电机可控硅励磁起励问题研究

自励恒压同步发电机起励时，依靠发电机的剩磁电压一般无法自建压，所以附加起励电源(一般为电池)。结合-200kW水轮发电机在具有附加起励电源且可控硅励磁整流电路工作正常情况下仍起励难的问题，分析并提出改进措施：提高辅助励磁电源；减小励磁变压器变比n；在整流输出侧并联电解电容。该发电机采用了第一种方法，辅助励磁电源提高到24V，发电机已能顺利快速起励，并能正常发电。     

浅谈托海水电厂发电机自并励励磁方式对机组后备保护的影响

简要分析了托海水电厂机组励磁系统由原自复励励磁方式改造为自并励励磁方式后，对机组后备保护-复合电压起动的过电流保护的影响及机组后备保护的改造方案。     

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。