限制广东500 kV电网短路电流运行方案

500 kV主网短路电流超标问题已成为广东电网近年来运行最突出的问题之一。对于开关设备不能及时更换的超标站点,只能暂时通过分层分区供电、分母运行、断开或跳通线路等措施,从系统运行方式安排上进行限制,将短路电流水平降低至安全合理的水平。以2009年广东500 kV电网以及其中的鹏城站为研究对象,从短路电流降低效果、实施的可行性、潮流分布、 N -1、系统可靠性等方面,对降低短路电流的各种运行措施进行了计算和研究,提出了相对较优的限制短路电流运行方案。     

一类复杂输电网络改进的可靠性评估模型

含500 kV/220 kV电磁环网的大型输电网通常采用“一次电网环网，二次电网分区开环”的运行方式，以减小短路容量，提高电网的安全稳定性。这一类复杂输电网络的可靠性评估面临着计算量庞大、状态分析困难等问题。提出了一种改进的可靠性模型，用具有多状态的等值发电机和等值负荷来简化二次电网，并对最小切负荷量的线性规划模型进行修正。该模型既保留了二次电网对一次电网的支持作用，又有效地改善了计算效率，极大地缩短了评估时间。通过对实际的大型交直流混合输电网进行算例分析，验证了该模型的有效性及可行性。     

限制500 kV电网短路电流的网架调整优化算法

通过开断部分线路调整500 kV网架结构以增加超标站点之间的电气距离,是限制500 kV电网短路电流的有效措施。对于开断线路的选择既要考虑短路电流的限制效果,又要尽量保持500 kV网架的完整性,如何从上千种断线组合中,选取一种开断最少线路以最大限度限制超标站点短路电流的断线组合极为困难。文中通过分析开断线路对阻抗矩阵各元素的影响,推导开断线路与超标站点自阻抗变化的灵敏度关系,并以该灵敏度为指标提出了一种限制500 kV短路电流的网架调整优化算法。该算法通过求取超标站点自阻抗灵敏度加权和的最大值,可以快速寻找限制超标点短路电流的最优断线组合,避免了对所有断线组合逐一进行校核的繁琐过程。基于该算法提出的广东电网500 kV调整方案证明了其有效性。     

四川省大渡河安谷水电站接入系统调整方案研究

由于乐山"十二五"电网网架发生较大变化等原因,需要对安谷水电站接入系统原方案作出调整,研究新的并网方案。推荐的调整方案为:安谷水电站将两回大截面220kV线路并入南天500kV站。经分析得知:该方案可靠性较高、施工可行性好、电网结构清晰、投资最少。电气计算表明:安谷水电站并网后乐山220kV网络潮流分布合理;需在南天500kV站每台主变中性点安装16Ω的小电抗才能将其单相短路电流限制在断路器遮断容量以内;在已订货的发电机暂态参数基础上,乐山电网220kV、500kV线路正常运行方式和检修运行方式下发生短路故障时乐山电网能够保持稳定运行。     

广东1 500 MVA大容量变压器短路阻抗的研究

研究了1 500 MVA/500 kV大容量变压器容量增大后对短路阻抗的影响，研究结果表明变压器容量增大后，为了控制短路电流，变压器短路阻抗也需相应增加，而变压器无功损耗与短路阻抗成正比，因此其容性无功补偿容量也需增加，并引起变压器中、低压侧电压波动升高。结合珠江三角洲负荷中心电网短路电流较高的特点，以东莞500 kV水乡站（4×1 500 MVA）为依托，从短路电流、容性无功补偿方面对1 500 MVA/500 kV大容量变压器短路阻抗进行了研究，提出了广东电网1 500 MVA/500 kV大容量变压器短路阻抗参数规范推荐意见。     

220kV变电站三相短路电流计算及结果应用

文章阐述了220 kV变电站的三相短路电流计算的重要性,并结合工程实例介绍了三相短路电流的计算过程及计算结果在变电站设计中的应用.     

桥式超导故障限流器的短路试验研究

电力系统传统的限制短路电流的方式是加装限流电抗器，但它在系统正常运行时 有电压降和能耗。中科院电工所在国家超导中心的支持下，研制了220 V/25 A桥式超导故 障限流器，它由NbTi超导磁体、二极管桥路和直流偏压源组成。将其接入电网，当电力系统 正常运行时，超导体电阻几乎为零，对电力系统运行无影响;当电网发生短路,超导线圈被 自动串入线路，从而限制了短路电流。在4.2 K温度下进行短路试验, 短路电流缩减率达40 %，有效地抑制了短路电流。     

暂态失稳引起大停电的可能性与对策研究

以某一将来实施分片运行的500 kV/220 kV规划电网为对象，从暂态稳定的角度对系统发生大面积停电的可能 性进行分析研究，并从电网规划、运行管理、继电保护和自动装置等方面，就预防大面积停电事故提出对 策。介绍了仿真计算所需的负荷模型、电源模型、输电线路模型、变压器模型等电网模型。     

考虑多分区无功电压优化的多Agent系统

针对电网分区管理的特点，采用以管理分区为计算单元的新的三级组织结构，将管理分区与优化分区有机结合起来，构建了多Agent系统。采用分解协调模型和辅助问题原理作为多Agent系统的算法，各分区并行计算，通过数据驱动的模型进行多Agent间的协商、协调，完成全网优化计算。文中以枣庄地区电网为例，建立了该系统的优化运行机制以及对现有多分区系统进行无功优化的方法。实际应用表明，该系统比不考虑多分区的优化方案加快了优化速度，降低了网损，提高了电压水平，为多Agent系统在大型电网无功电压优化中的应用提供了更加实用化的解决方案。     

电流融冰法在郴州市电网的应用

文章介绍了郴州市地方电网为保护郴州市电网输电线路而采用的一种三相直接短路电流融冰法,并重点介绍了邓家塘——满天星110kV输电线路融冰设计及其实施。     

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。