水轮机可编程调速器若干问题研究

 为了提高水轮机调速器可靠性和性能指标,满足水电厂日益提高的自动化水平和人们的审美 观念,对水轮机可编程调速器的测频、人机界面、采样周期、通讯、故障处理、参数设置、 电源等问题进行了分析研究。提出了静态测频和动态测频概念及动、静态测频值计算式,并 将原PLC外部测频改进为内部测频。调速器的人机界面采用了先进美观的汉字显示触摸屏,同 时配置有标准的RS232串口或RS485串口。通过软件编写和采用常数扫描应用功能,使PLC调速 器采样周期不等问题得到改善。分析研究的结果,已得到实际工程的验证,可供设计选用。     

基于可编程逻辑控制器的微机调速器测频方法

水轮机调速器性能提高的关键是测频系统,测频精度和实时性是描述测频系统好坏的重要标志.大幅提高水轮机调速器频率测量的可靠性对机组的安全稳定运行起着极大的作用.传统的可编程逻辑控制器(PLC)调速器测频方式由于接口的原因,往往会在精度和实时性上互相矛盾,故PLC测频成为制约调速器发展的瓶颈.针对这种情况,分析了现今比较流行的PLC测频方法,提出了能够保证精度和实时性的PLC测频方法.对基于PLC调速器的直接测周期法以及精度和实时性指标进行了具体分析.     

水轮机微机调速器测频方式与方法的探讨

就微机调速器的测频方式、测频的冗余、数字测频硬件选择、测频分辨率与测频采样周期、PLC调速器测频方法、PCC调速器测频、齿盘测速回路等方面展开分析,希望能对微机调速器的研发、设计、验收、标准制定等相关部门提供参考性的意见和建议.     

微机冗余测频组件的研究

频率测量是水轮机调速器的关键环节之一,其测量精度、可靠性及速动性对水轮机调节系统的动、静态品质至关重要。本文提出的三路冗余测频方法,可大大提高频率测量环节的精度、可靠性和抗干扰能力。同时,使得测频采样周期缩小到10ms左右。     

基于PLC外加计数模块的水轮机调速器频率测量

作为水轮机调节的基础,水轮机调速器频率测量中的测频准确度和精度,与水轮机的安全运行息息相关。在其频率测量方式中,基于可编程控制器（PLC）的水轮机调速器频率测量,具有易于编程、精度高以及维护方便等特点,已成为水轮机调速器测频主流,其主要形式有基于PLC的内部高速计数器和基于PLC的外加高速计数模块2种。主要介绍了运用外加施耐德BMX EHC 0200高速计数模块进行频率测量的原理;同时,也对其所具有的特点、频率计算过程与计算方式等作了简单描述。     

基于PCC的步进式水轮机调速器软硬件系统分析

针对目前小型水电站水轮机调速器运行中存在的问题,通过调研推荐一种具有高可靠性的PPC步进式水轮机调速器,并结合小型水电站调速器运行特点,对其硬件和软件系统进行了分析.结果表明,与其他调速器相比,该类型调速器的可编程计算机控制器测频模块配以适当软件可直接测量频率信号的当前周期,计数脉冲频率达4MHz以上,平均无故障率达50万h,且CPU模块为多处理器结构,使主CPU的资源得到合理使用,最大限度地提高了调节速度,具有良好的动静态特性,适用于中小型水电站     

PLC调速器中采样周期不等性问题研究

PLC(可编程序控制器)水轮机调速器中控制调节的采样周期为其程序执行的扫描周期，存在 不等性。仿真研究和实际投运表明，由此设计的PLC调速器，仍可保证调节系统具有较好的 动态品质。     

抽水蓄能机组调速器测频的研究

分析了水轮机调速器测频环节的各个方面,包括测频原理、测频方法、测频信号来源、测频冗余等;最后介绍了桐柏抽水蓄能电站调速器有关测频方面的硬件、软件配置与设计,希望能对调速器测频的研发、设计等提供一定的参考意见。     

PLC调速器在鲇鱼山水电站的应用

1简介 DJT系列全可编程中型调速器是一种全新的中型水轮机调速器，电气部分采用日本三菱电机的FX2N系列可编程作为硬件；采用伺服电机作为液压的转换元件；人机界面采用先进的触摸显示屏，维护更为简便、直观；测频方法采用纯PLC测频方式，使得测频精度更高，整机性能更稳定。机械部分由电动集成随动装置和压力油源组成，二者合成一体，电动集成随动装置由电动集成阀（具有液压输入）、液压反馈的主配压阀、液控单向阀、紧急停机电磁阀、滤油器及主接力器等构成，其特点除了工作可靠，性能优良外，更突出的是结构十分简单，制造、调试、运行、检修均更为方便。     

水轮机调速器设计、选型若干问题探讨

水轮机调速器的品质与性能直接影响电能的品质和水电站的安全可靠运行。根据多年的水轮机调速器技术改造和运行维护经验,就水轮机设计、选型过程中如何合理解决水轮机调速器测频回路、电气—机械转换部件、导叶位置反馈、调速器辅助功能设置等问题进行了探讨。     

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。     

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。     

Fish assemblage response to recent mitigation of a channelized warmwater stream

Various designs of low‐head dams are used to rehabilitate streams or forestall upstream channel incision after channelization. We report on the efficacy of using notched sills and grade control structures (GCS) to restore the fish assemblage in Luxapallila Creek, Mississippi. We tested the null hypotheses that habitat variables and species richness, evenness, and assemblage structure would not differ among: (1) a channelized segment with no modifications; (2) a channelized segment mitigated by the installation of sills and GCS; (3) a segment upstream of the installations and undergoing channel incision; and (4) an unaltered segment. Although habitat variables changed, neither species richness, evenness, nor fish assemblage structure differed between mitigated and channelized segments with both exhibiting less richness and different assemblage structures than the unaltered segment. Lack of differences in species richness between the incised and unaltered segments suggest that the GCS may have halted the negative effects of upstream channel incision before species were extirpated. Conspicuous habitat differences between the altered (channelized and mitigated) and unaltered segments were lack of backwaters and canopy coverage and finer substrates in the altered segments. Our results suggest a more comprehensive rehabilitation strategy is required in Luxapallila Creek. Published in 2003 by John Wiley & Sons, Ltd.     

NUMERICAL STUDY OF WAVE EFFECTS ON SURFACE WIND STRESS AND SURFACE MIXING LENGTH BY THREE-DIMENSIONAL CIRCULATION MODELING

1. INTRODUCTION Coastal and continental shelf regions are characterized by intensive interaction between wave and current. These regions are of great economic significance to mankind. Therefore, the modeling of wave and current as well as their mutual int…