类工频电流电压降法在公伯峡水电站接地网接地电阻测试中的应用

公伯峡水电站是一座以发电为主综合利用的水利枢纽工程。该电站安装5台水轮发电机组，单机容量300MW，总装机容量1500MW。电站采用330kV一级电压接入系统，与西北330kV电网联网。电站主要承担西北电力的系统基荷、调峰，同时承担系统的调频和事故备用，是西北电网的主力电站之厂。该电站接地网以及接地电阻是否满足要求是保证电站安全运行的重要条件。文章介绍了类工频电流电压降法在黄河公伯峡水电站接地网接地电阻测试中的应用以及公伯峡水电站接地网接地电阻测试方案及测试结果。     

浅谈降低接地装置接地电阻的措施

针对接地网问题引起的事故和雷击引发的电网事故,就降低接地装置的接地电阻进行了探讨,提出了建设性意见.     

某大型机组励磁系统非线性电阻烧伤处理

为了更好地了解水力发电机组灭磁电阻的特性及其相关试验过程,以国内某大型水电站为例,分析了其发电机组励磁系统SiC非线性灭磁电阻的局部烧毁故障,并对其灭磁电阻的小电流温升状况进行了试验。结果表明,当灭磁电阻特性存在缺陷时,会对机组的安全运行产生较大的隐患。对灭磁电阻出现事故的背景及其原因分析、对事故所采取的处理措施、模拟试验程序及分析结果等作了描述。     

SiC灭磁电阻最大能容量与均能均温系数关系探讨

国内大量的大、巨型发电机组配置引进SiC灭磁电阻,近20年在运行、事故灭磁、试验中出现一些事故故障。文中通过对外商标准、事故调查、试验数据和鉴定会资料的研究,对SiC灭磁电阻事故原因及其最大能容量与均能均温系数的关系进行探讨,可供发电厂发电机灭磁装置设计、招标、运行、维修参考。     

大岗山水电站4F机组定子线棒击穿原因浅析

根据大岗山水电站4F机组在运行过程中由于测温电阻垫条烧损引起发电机定子接地,致使机组出口开关跳闸,机组被迫停机检修的具体情况,分别对1F、2F、3F机组定子线圈测温引线开展了逐项排查工作。虽然机组大部分定子线圈测温引线屏蔽层对地、主备电阻屏蔽层间绝缘良好,但也存在部分电阻屏蔽层接地、主备电阻屏蔽层短路等异常现象。通过采取有效的措施,对已损毁部件更换,对各薄弱部位进行可靠的绝缘处理,在运行过程中加强监视定子线圈测温故障,在发电机定子下线时对厂家供应的测温电阻垫条进行严格检查、测试和采取必要的措施,以防同类事故的再次发生。     

500 kV输电线路断路器合闸电阻配置原则

通过对某500 kV输电线路断路器取消合闸电阻的投切试验、断路器事故进行分析，并对此进行电磁暂态仿真计算，讨论了500 kV输电线路断路器取消合闸电阻的原则，与线路操作过电压幅值、线路两端高压并联电抗器配置情况的关系。研究结果表明，500 kV输电线路断路器合闸电阻配置时，需要考虑线路高压并联电抗器的配置情况，这将直接影响断路器断开的成功与否。     

一起10kV母线停电事故的成因分析

以一起造成某公司生产系统停车的10 kV母线停电事故为例,介绍了事故现象和保护装置动作情况,分析了事故原因,论述了中性点经电阻接地系统的特点,指出了中性点接地方式的发展趋势。     

浅析瑞丽江水电站机组瓦温测量系统改造

瑞丽江水电站机组瓦温测量系统发生过两次非计划停运事故和多次故障报警,主要原因是环境、测温电阻质量、系统回路过于简单及监控系统事故停机流程缺陷等.针对与此.电站对测温接线回路和机组LCU二类机械事故控制流程进行了改造,并梳理了转接端子箱内部,为日常维护提供了可靠的保障,从而保证了机组的高效率运行和电网的安全稳定运行.     

重视电气设备的接触电阻

黑石电站电气设备的接触电阻过大且不对称,发生指示仪表不准确而引发的故障和事故占设备事故的90％以上。经分析,认为影响接触电阻的因素是接线端头接触面的材料、压力、表面状况、固定接触的尺寸、温度及接触形式等。要做好接线端头接触面的日常维护工作,即采用化学性能稳定的金属材料银、铂、铱及其合金等;镀上不易氧化的材料;用滚动、滑动触头的办法来消除氧化膜;维护中严格按工艺标准实施。重视设备的接触电阻试验,检查是否超过规定值,以防止事故发生。     

关于发电机转子接地保护几个问题的探讨

分析了轴电压吸收回路以及接地碳刷与大轴间接触电阻对发电机转子接地保护的影响,并分别提出了相应的对策和注意事项。可通过延长电子开关切换周期或方波电源周期消除轴电压吸收回路的影响,应保持接地碳刷与转子大轴间接触良好。探讨了旋转励磁机组转子接地保护的构成方式,建议采用定期检测方式。     

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。