Analysis of causes of the melting of contact devices in the current leads of rotors in TVF turbogenerators

Results of analysis of the melting of rotor leads in turbogenerators during the period from 2001 through 2005 are presented. A distribution of the number of damages sustained by generators with respect to type, time, type of studs, active and reactive loads at the time of failure, etc. is given. It is established on the basis of electric-contact theory that one of the basic causes of the melting of the contact components of rotor leads is misalignment of the head slots of the contact stud and its skewness in the threaded hole of the contact rod. Recommendations are given for prevention of misalignment of current leads.     

边界效应确定混凝土断裂能的简化计算

从试件边界条件对韧带上断裂性能分布的影响出发,合理假定局部断裂能的光滑连续曲线分布,给出了与试件尺寸无关的混凝土断裂能及边界效应参数的计算模型。以不同高度的三点弯曲梁试验数据进行了分析计算并讨论了试件尺寸的选取问题。结果表明用两个试件尺寸就可以确定与试件尺寸无关的混凝土基本断裂参数,从而简化了模型中对多个试件尺寸的要求,但只有适当选取试件的两个尺寸,才能正确给出混凝土的断裂能和边界效应参数。     

黄河流域干旱频率分布及轮次数字特征分析

从黄河流域干旱的研究现状以及方法论出发,利用游程分析理论,分析了1001—2000年黄河流域部分监测点每100 a的干旱年数,对1470—2000年黄河流域20个监测点的统计数据进行游程理论的数字特征计算,绘制了黄河流域各监测点的干旱重现期等值线图,利用K-means方法对监测点的数字特征进行了分类。结果表明:黄河流域各监测点的干旱年数呈总体上升趋势,1401—1700年,所有监测点的干旱年数不断增加,1701—1900年各监测点的干旱年数最低在每百年20次,20世纪至今干旱有增多趋势;产生重要影响的频繁干旱易发生于黄土高原、华北平原;长治、德州、太原、临汾、济南、西安等地区比其他地区在较长时间内更容易发生大旱,且连旱年数更长。     

灌区渠道防渗的节水技术

随着水资源的短缺,提高农用水效率已迫在眉睫,而渠道防渗是当前灌区节水改造的重要内容之一,也是节水灌溉的重要途径。介绍了渠道防渗的各种措施及其优缺点,并从渠道规划设计、采用的衬砌材料不同及输水断面形式的不同三个方面加以阐述,重点提到了北方渠道的防冻涨破坏的要求,结合东北地区自然条件和社会经济条件提出了几种既适用又极易推广的渠道防渗措施。     

The Problem of Coordination of Levels of Short-Circuit Currents in Power Systems

The problem of coordination of short-circuit (fault) currents is considered. Data on the dynamics of variation of the levels of single-phase and three-phase short-circuit currents (their highest values) in networks rated for different voltage are presented for a long-term period. The main factors (integral parameters of the networks) affecting the values of short-circuit currents are listed. Statistics of variation of rated parameters of electrical equipment in past years and in the recent period is presented and predictions for the future are made. Basic methods and means for limiting short-circuit currents are discussed. A method of automatic and stationary network separation and a method of circuit design are described in detail. The efficiencies of different methods are compared. The effect of integral parameters of the network on the maximum level of short-circuit currents is shown. The aspects of the switching life of breakers and of allowance for probabilistic characteristics of faults and for the risk factor of decision-making are considered. It is shown that coordination of the levels of short-circuit currents is a possible means for raising the reliability of power installations and systems.__________Translated from Elektricheskie Stantsii, No. 4, April 2005, pp. 19 – 32.     

Error of the Method of Determination of the Place of Damage of Overhead Lines Due to Ignored Phase Differences in Its Parameters

The effect of neglecting the influence of the phase asymmetry of parameters of overhead lines (OL) of different voltage classes on the accuracy of determination of the place of damage is discussed. The effect of phase transposition on the error of determination of the place of damage of a transmission line is evaluated by the methods of one-sided and two-sided measurement of the parameters of emergency operation. A method and software is suggested for substantial reduction of the error of the method of determination of the place of damage of overhead lines.     

Estimation of flood losses

Conclusion The problem of organizing protection of territories and prevention or minimization of losses from floods and freshets affecting the interests of people in practically all regions of the world should be solved on the basis of the combined use of all means of protection, both engineering and nonengineering, on the basis of consideration of the interests of the development of society without any substantial disturbances of the environment.Translated from Gidrotechnicheskoe Stroitel'stvo, No. 4, pp. 4–8, April, 1991.     

Experience in antiseepage works on concrete structures of the Paz hydroelectric stations

Conclusions Seepage of water through concrete structures has a broad spectrum of pressure and free-flow manifestations, location and the source and outlet, causes of occurrence, and external forms of leaching accompanying it;On hydraulic structures seepage is local, occurring along defective sections and points of the concrete;Long-term observations prove the gradual decrease of the seepage rate as a whole for structures of the cascade of Paz hydrostations and the dependence of the character of its variation seasonally on the site of seepage;Antiseepage measures on operating objects are diverse both with respect to general direction (suppression, diversion, or isolation) and methods of realization. Their selection is determined both by the structural characteristics and purpose of the works (elimination of seepage centers, protection of structures and equipment, cosmetic purposes, provision of safety for the personnel);New methods of sealing concrete on structures of the cascade were tested: pneumatic injection of dry cement and a solution of colophony in acetone.Seepage centers in powerhouses and dams occur not only from the head of water but also from the effect of factors common for all construction objects, such as precipitation, groundwaters, leaks from engineering supply lines; the experience in eliminating such centers was not examined in the article;The increase of the presence of defects as a consequence of the long effect of seepage, even diminishing seepage, and the noted increase of its rate in individual places require an increase of the scope of antiseepage works.Translated from Gidrotekhnicheskoe Stroitel'stvo, No. 2, pp. 34–39, February, 1993.     

太湖流域设计暴雨的时空分布计算

利用太湖流域1951-2010年的雨量资料,从平均暴雨日数和最大30 d雨量两个方面,分析流域暴雨时空分布特性。太湖流域多年平均暴雨日数、多年平均最大30 d雨量在时间分布上都呈增加趋势但不显著,在空间分布上山丘区均大于平原区。通过对流域和分区时段雨量的重现期进行统计分析,提出两种可能的流域设计暴雨空间组合方案及反映太湖流域暴雨特点的设计暴雨时空分布计算方法,结果表明本文提出的针对太湖暴雨特点设计的暴雨空间组合方案及计算方法合理。     

发电机内部故障仿真分析软件的基本原理

将交流电机的多回路分析法应用于发电机内部故障分析计算，编制了仿真计算软件，介绍了软件的特点、界面和结构。该软件考虑了气隙谐波磁场、绕组的各种连结方式、线圈空间位置的影响，可以用来分析交流电机各种形式的内部和外部故障，计算电机所有电压和电流等电气量，定子任意支路电流的组合用于各种保护方案的分析。该软件适合于大中型发电机主保护设计整定计算，是发电机内部故障分析方法与主保护设计的创新。     

预应力钢丝松弛对超大口径PCCP承载能力的影响

以南水北调中线工程为背景,利用光纤光栅计测取预应力钢丝实际松弛量。基于试验结果,采用非线性有限元法建立了PCCP承载数值计算分析模型,进行了钢丝预应力松弛对PCCP承载能力的影响研究。计算结果表明:在正常使用极限状态和弹性极限状态下,PCCP内压值随预应力松弛量的增加而减小;在承载能力极限状态时PCCP内压值保持不变。基于现场测试结果和计算结果,评价了预应力松弛对PCCP承载能力的影响,为PCCP的生产和运行积累了工程经验,为制定超大口径PCCP标准以及质量验收提供依据。     

人工砂石料智能设计系统研究

在分析人工砂石料系统的特点及其计算机辅助设计应用现状的基础上，提出了一种多Agent协同工作的人工砂石料智能设计系统的实施方案。由野外勘测资料、采料场优选、工艺流程设计、堆场规划、加工厂布置、技经评估、项目管理7个Agent和工程数据库配合构成的系统，易于实现人工砂石料系统设计的智能化、集成化、网络化，能大幅度提高设计质量和效率。     

土体强度指标的互相关性对堤防稳定性的影响

对黄河下游堤防各类土体凝聚力与内摩擦角之间的相关性及其对堤防稳定性指标的影响进行了分析,结果表明：土体强度指标的互相关性对黄河下游堤防边坡稳定性评价影响较大;采用固定的土性参数来计算其稳定性是不切合实际的;土体抗剪强度参数的相关性是计算边坡可靠指标的一个极其重要的因素。     

爆破震动瞬时能量与岩体相对位移响应的关联性研究

通过结构动力方程求解得到岩体相对位移响应过程,以EEMD-HHT信号分析方法获得岩体爆破震动信号瞬时能量,在时域内进行分析研究岩体爆破震动信号瞬时能量与岩体相对位移响应的关系,发现岩体最大相对位移响应值滞后于爆破震动信号最大瞬时能量值的时刻;在时域内岩体相对位移响应过程曲线与爆破震动信号能量幅值并非相互对应,但与爆破震动速度时程曲线具有一定的关联性,这表明爆破震动激励下岩体相对位移响应值的大小与爆破震动能量、岩体的自振周期、爆破震动类型有关。     

黄河源区径流变化及原因分析

采用斯波曼秩次相关法分析了黄河源区20世纪60年代以来径流变化情况,并从降水、气温、下垫面等影响因素探讨了黄河源区径流变化原因。结果表明:①黄河源区的径流年际变化从60年代以来有明显的阶段性变化,从年内变化来看,唐乃亥站的汛期和非汛期径流量占年径流量的比例也具有阶段性变化,从80年代中期到90年代末,汛期径流量占年径流量的比例一直减少,非汛期径流量所占比例一直增大。②过去40多a来,玛多站年降水量呈现出缓慢上升的趋势,玛曲站则呈现出下降的趋势;从降水年内变化来看,雨季降水量占年降水量的比例呈减少趋势,旱季降水量占年降水量的比例呈增加趋势。因此,黄河源区降水量的变化是影响径流变化的主要原因,90年代小雨多、降雨历时长是导致径流减少的另一个原因。③黄河源区径流的变化,特别是90年代径流量的偏小和气温的直接关系不大。④植被覆盖面积的变化并不是引起径流减少的原因。     

EFFECT OF SUSPENDED PARTICLE ON STABILITY OF INTERFACE OF MOVING TWO-PHASE JET

ＮＯＭＥＮＣＬＡＴＵＲＥαｓｐａｒｔｉｃｌｅｖｏｌｕｍｅｆｒａｃｔｉｏｎｕｇｉｎｓｔａｎｔａｎｅｏｕｓｇａｓｖｅｌｏｃｉｔｙｖｅｃｔｏｒｕｓｉｎｓｔａｎｔａｎｅｏｕｓｐａｒｔｉｃｌｅｖｅｌｏｃｉｔｙｖｅｃｔｏｒＵｍｅａｎａｘｉａｌｖｅｌｏｃｉｔｙｏｆ...     

纤维混凝土在水工建筑工程中的应用(下)

概述改性混凝土的发展情况,介绍纤维混凝土在国内外水工建筑物上的应用实例,提出钢纤维增强钢筋混凝土水工建筑结构强度计算方法,包括受弯构件正截面强度、斜截面抗剪强度的计算;重点介绍网状钢纤维增强混凝土（FOC）在水工建筑物上的应用,包括在渡槽、闸门、小型拦河坝、轻型岸壁等工程上的应用实例,T形梁正斜截面的强度计算,板材承载力计算的方法。     

水布垭面板堆石坝坝体后期变形时空分布规律研究

通过分析水布垭面板堆石坝的长期实测变形资料,对最大坝高断面和下游坝面的后期变形情况进行研究,揭示了坝体后期变形的时空分布规律.研究表明:沉降是坝体后期变形的主要形式;后期沉降增量基本随高程升高而增大,但后期水平位移增量的分布未表现出与高程的相关性;下游坝面后期变形阶段的三向变形增量的分布规律与面板堆石坝一般变形规律类似...     

心墙体积的改变对高土石坝内渗流场的影响研究

在心墙土石坝设计中,心墙是土石坝的防渗主体,它对坝的稳定起着至关重要的作用。该文结合工程的实际情况,考虑非饱和区的影响,在不同心墙体积的情况下,分别对其进行渗流计算分析,来探讨渗流场的分布情况和自由面的变化规律,为大坝结构设计和施工提供基础资料和参考依据。