HVDC孤岛交流系统中水轮机调速器特殊问题分析

HVDC(High Voltage Direct Current)送端为巨型水电站或水电站群时,采用孤岛运行方式,可以避免HVDC系统故障时对附近交流大电网稳定的不利影响,但在采用孤岛方式运行的情况下,一旦发生故障导致极闭锁引起输送功率大幅跌落,将会出现关于水轮机调速器控制的新问题。本文指出HVDC孤岛水电交流系统的特殊性和研究意义,然后结合云广直流工程实例,讨论与分析了HVDC极闭锁故障下水电孤岛系统调速控制中的特殊问题。     

机组溜负荷原因分析及处理

甘肃小峡水电站4号水轮发电机组由于同期装置和监控系统之间存在寄生回路,自投运以来,曾发生两次直流系统一点接地时机组溜负荷事故,最严重的一次导致机组事故停机。电站在4号机组正常运行情况下,通过大量电气试验,查明原因,并进行了相应的处理。处理后经过多次直流系统一点接地试验,机组运行正常。     

水电站直流系统故障处理探讨

水电站直流系统主要供给继电保护、自动装置、计算机监控、机组起励、UPS装置、事故照明等装置的工作电源,因此,对直流系统的运行可靠性要求很高。本文简要阐述了水电站直流系统的故障危害、故障分析、故障处理以及故障处理时的原则及注意事项。     

广东粤电长潭发电公司转子磁极改造

广东粤电长潭发电公司3台机组转子一点接地情况,针对机组转子的磁极线圈引线和磁极问连接头存在的缺陷,阐述四台机组转子的改进工艺。经改造,既消除了机组缺陷,保证机组的安全稳定运行,又减小了转子绕组直流电阻,降低机组转子的激磁损耗。     

锦屏二级水电站避沙运行方式风险分析及管控措施研究

在库区水流泥沙含量较高时,锦屏二级水电站需采取避沙运行方式,以降低泥沙对机组运行的不利影响。但避沙运行期间的特殊工况也将对电站的安全稳定运行提出严峻考验,故针对锦屏二级水电站的避沙运行方式进行了风险分析,最后提出的对应管控措施可有效应对电站避沙运行过程中可能产生的各种风险。     

小湾巨型水电站计算机监控系统在孤岛模式下的控制与实现

基于小湾巨型水电站孤岛运行的背景,首先阐述了巨型水电站孤岛运行面临的问题,然后着重阐述小湾水电站数据采集与监控系统在孤岛运行中的信号传递和控制策略.最后,以目前孤岛试验的阶段性成果为实例,验证了所述控制策略,为小湾水电站孤岛模式常态化运行打下了坚实的基础.     

紫兰坝水电站机组蠕动原因浅析与处理

浅析紫兰坝水电站机组蠕动的各种可能原因,找出主要原因,提出处理措施。同时,结合工作实践经验,提出能够使蠕动机组停稳的现场应急处理方法,供运行人员参考学习,确保运行人员遇到机组蠕动情况时能迅速做出正确响应,避免处理不当造成事故。     

高压直流配套电厂孤岛信号逻辑判别分析及应用

配套高压直流输电的电厂在直流输电工程投产前需完成设备的适应性改造工作,其中直流孤岛判别系统是换流站及电厂设备正确进行自动控制的前提,孤岛判别指令的正确及可靠性是电厂适应直流各种运行方式,保障电网及电厂设备安全稳定运行的关键。结合金中直流及梨园、阿海电厂的孤岛系统,分析配套电厂侧的孤岛信号逻辑判别设备配置及系统逻辑,给出高压直流配套电厂侧设备孤岛信号逻辑判别的实现方案。     

贵州省黄花寨水电站接地优化设计分析

将黄花寨水电站接地电阻的设计要求与现场实际情况相结合,对该电站接地电阻偏高影响因素进行分析,探讨各种切实可行的降低接地电阻的方法,并提出相应的处理对策方案.电站第1台机组投入运行前,采用交流电压、直流直线法测试现场接地电阻,测试结果表明,优化后的接地系统能够满足该站安全可靠运行性能指标要求.     

安口水电站机组抬机的分析与处理

安口水电站自运行以来,机组的出力、温度、振动等各项指标均正常,但是机组在甩负荷时发生抬机现象,给电站安全运行带来隐患.通过实践,从多个角度并应用多种方法对其进行了分析,最终用较简易的方法解决了电站抬机的问题.图2幅.     

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。     

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。