TPY级电流互感器在班多水电站中的应用

具有暂态误差性能的TPY电流互感器广泛应用于高电压等级电力系统及大容量发电机变压器组的差动保护中。文章简要介绍了班多水电站变压器差动保护选择TPY电流互感器的原因,并介绍了TPY电流互感器参数选择及校验的计算方法。指出了针对中小型机组接入大系统,选择TPY型电流互感器参数的重点,并列举说明了校验TPY电流互感器等效二次极限电动势及暂态误差不满足规范要求情况下的解决办法。     

水电站典型厂用变支路接线及继电保护配置分析

对水电站3种比较典型的厂用变支路接线进行分析,讨论在厂用变支路分别采用真空发电机断路器、限流熔断器和负荷开关组合以及离相封闭母线直接连接的情况下,厂用变支路的保护用电流互感器参数选择和继电保护配置的解决方案。     

Operating Conditions of Direct-Current Transmission Lines and Back-to-Back Direct-Current Converter Stations Employing Voltage Converters

Special features of steady-state and transient operating conditions of direct current transmission (DCT) lines and back-to-back direct-current converter stations (BBS) based on voltage converters (VC) on fully controlled valves (FCV) are considered. An electrodynamic model developed by NIIPT, which includes physical models of BBS and DCT, is used in the study. Converters of the type are shown to be capable of virtually inertialess control of the active power flow, including the possibility of its reversal, of control of reactive power in the inductive and capacitive quadrants, and of operation under conditions of low short-circuit ratios and autonomous demand. The principles of control of BBS on FCV in a voltage conversion system under transient conditions are formulated, one of the aims of which is prevention of current and voltage overloads on the equipment.     

静载荷试验确定复合地基承载力的安全储备研究

未加载充分的现场静载荷试验不能完全反映地基承载力情况,有可能导致复合地基安全储备过高。结合闽东沿海某工程,在静载荷试验未加载充分的情况下,利用灰色模型预测了单桩和复合地基的极限承载力。同时,定义复合地基承载力极限值与按相对变形确定的特征值之比为K,K是一个反映复合地基承载力安全储备的安全系数。通过统计同地区113组复合地基静载荷试验结果,确定了水泥土搅拌桩复合地基的K值。经过验证,K值同样适用于该工程。因此K具有一定地区性,在根据相对变形确定复合地基承载力特征值后,利用K可以一定程度上预测复合地基承载力极限值,从而为较直观认知复合地基的安全储备提供参考。     

岩石非均质构成对宏观力学特性的影响研究

利用岩石矿物细胞元随机性参数赋值方法描述岩石的非均质构成,分别针对2类矿物细胞元和3类矿物细胞元构成的非均质岩石模型,研究了岩石非均质构成对其宏观应力-应变关系曲线的影响。基于岩石矿物构成定义了岩石的非均质度,根据数值模拟计算结果分析了岩石非均质度对岩石宏观力学参数（宏观弹性模量、极限强度）的影响。研究结果表明：均质岩石宏观力学特性由细胞元力学特性决定,非均质岩石宏观力学特性由细胞元力学特性和岩石非均质构成共同决定;在非均质度较小时,宏观弹性模量受岩石非均质性的弱化影响较小,反之,当非均质度较大时,宏观弹性模量受非均质性的弱化影响较大;宏观极限强度受岩石非均质性的弱化影响趋势与宏观弹性模量一致。     

真三轴应力下混凝土的动态力学性能及破坏准则

为研究混凝土结构处于复杂应力状态下的静动态力学特性,进行了不同应力比及加载速率下的真三轴压缩试验。对混凝土的强度特性和变形特性展开了深入分析,并基于八面体应力空间建立了考虑应变速率效应的真三轴动态破坏准则。结果表明:真三轴受压下的混凝土极限抗压强度随着应力比的增大而增大。随着应变速率的增加,应力比较低时,混凝土的极限抗压强度逐渐增大;应力比较高时,极限抗压强度先减小后增加。随着应变速率的增加,侧向变形曲线的破坏峰值点更明显;随着应力比的增大,侧应力较大方向上的变形越来越小。基于八面体应力空间建立的真三轴动态破坏准则表达式中包含3个率效应参数,经验证与试验数据吻合较好。     

电脉冲信号暂态响应法评定钢筋腐蚀状态

钢筋混凝土结构物中的钢筋腐蚀检测评估的新方法－电脉冲信号暂态响应法，具有快速、无损和判别准确率高的特点，它运用计算机采集处理钢筋在恒电流脉冲作 的电位暂态响应数据。求出反映钢筋腐蚀状态的特征参数－阻容（R C）值，室内试验和现场检测表明，钢筋的RC 值主要与钢筋的腐蚀状态有关。RC值小于4.4s，钢筋即腐蚀。     

Multi-point design optimization of hydrofoil for marine current turbine

The comprehensive performance of the marine current turbine is an important issue in the ocean energy development. Its key is the performance of the hydrofoil, which is used to form the turbine blade. A multi-point optimization method of the hydrofoil is proposed in this paper. In this method, the Bezier curve is used to parameterize the hydrofoil. The geometrical parameters are used as variables while the lift-drag ratio and the cavitation performance of the hydrofoil are used as the objective functions. The NSGA-II algorithm is chosen as the optimization algorithm. In order to resolve the difficulty of this high-dimensional multi-objective optimi- zation problem, the conception of the distance metric in the metric space is introduced to unify the lift-drag ratio and the cavitation performance under different working conditions. And then, the above optimization method is applied in the NACA63-815 hydro- foil＇s optimal design under three typical conditions. Finally, the results from the performance comparison of the original and optimi- zed hydrofoils obtained by using the CFD simulation are analyzed in detail. It is indicated that the optimized hydrofoils enjoy a better hydrodynamic performance than the original ones under the three conditions. The feasibility and the theoretical validity of this optimization method are confirmed by the results.     

倾斜荷载作用下沉箱基础的极限承载力计算方法

为了确定沉箱基础在顶部受到倾斜荷载时的抗拔承载力,利用极限包络线方法进行分析。基于15组模型试验以及合理假定,提出了水平荷载、竖向荷载作用下沉箱基础的极限抗拔承载力函数,通过分析水平、竖向极限承载力系数与长径比的关系,提出了水平、竖向荷载作用下沉箱基础的承载力计算方法。基于不同长径比、不同荷载作用角度下沉箱基础的水平承载力归一化分量和竖向承载力归一化分量之间的破坏包络线图,得到了两者之间的幂函数关系,从而得到了沉箱基础在倾斜荷载作用下的极限承载力。     

A study of algorithms of longitudinal differential protection of generators and generator-transformer units

A comparative analysis of two principal algorithms of operation of differential protection of generators and transformers is presented. The behavior of relay protection devices based on the algorithms is considered, especially under transients. The behavior of the algorithms is studied under steady conditions and under transient conditions accompanied by the appearance of fault currents with aperiodic components that saturate the cores of current transformers. Amethod for improving the selectivity and reliability of operation of devices for differential protection of generators and transformers is suggested. __________ Translated from élektricheskie Stantsii, No. 2, February 2006, pp. 46–50.     

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。     

离岸深水全直桩码头水平承载力简化计算

全直桩码头是一种适用于离岸深水海域的新型高桩码头结构型式,其破坏模式与传统高桩码头结构存在较大差异。通过有限元法研究了水平荷载作用下离岸深水全直桩码头结构破坏模式、桩侧土压力及桩身弯矩分布,并验算了规范中m法、P-Y曲线法和NL法的适用性。研究结果表明,水平荷载作用下,基桩的塑性破坏是结构失稳的控制因素,且结构失稳时桩身最大弯矩达极限弯矩值,在此基础上,结合简化计算方法计算了结构水平极限承载力。通过对比可知,基于m法的简化方法在小位移时与有限元法吻合较好,基于P-Y曲线法和NL法的简化方法在各种位移条件下与有限元法均吻合较好,且通过桩身极限弯矩与设计荷载作用下桩身最大弯矩之比计算结构安全系数的简化方法是合理的。     

Assessing the role of biochemical methane potential tests in determining anaerobic degradability rate and extent

The biodegradability and bioavailability of hydrolysis-limited substrates under anaerobic (and aerobic) conditions can be represented by two key parameters--degradability (f(d)), or the percentage that can be effectively be destroyed during digestion, and first order hydrolysis coefficient (k(hyd)), or the speed at which material breaks down. Biochemical methane potential (BMP) testing uses a batch test (in triplicate), and by fitting against a first order model, can fit both parameters in the same test. BMP testing is now being widely used for anaerobic process feasibility and design purposes, and standardisation efforts are ongoing. In this paper, we address a number of key issues relating to the test method and its analysis. This includes proposal of a new fitting and parameter estimation method, evaluation of the impact of inoculum to substrate ratio on fitted parameters, and comparison to performance in continuous systems. The new parameter estimation technique provides an estimate of parameter uncertainty and correlation, and is clearly more suitable than model transformation and linear regression. An inoculum volume ratio of at least 50% (2:1 on VS basis) was required on a cellulose substrate to use methane production as primary indicator, as found by comparing methane production and solubilisation of cellulose. Finally, on a typical material, waste activated sludge, the batch test was slightly conservative in terms of degradability and rate, indicating a bias in the BMP test. The test is a cost-effective and capable method to evaluate potential substrates, but it should be noted that it is generally conservative, especially if sub-optimal inoculum is used.     

珠江三角洲河网径流输运过程对河床地貌的影响

通过珠江河口平面二维潮流数学模型,对不同地形条件下珠江三角洲河网区径流输运过程进行了分析。结果显示河床下切导致蕉门、虎门的潮汐动力加强,分流比减小,而磨刀门的分流比则有所增加。由于河床容积的增加,主要河道余流流速均有所减少,但由于北江干流分流比的下降,其余流流速减小趋势尤为明显。     

海水冻融后轻骨料混凝土的双轴压压强度和变形性能

针对我国渤海湾北部海域轻骨料混凝土结构的工作环境和受力状态，进行了海水中不同冻融循环次数后轻骨料混凝土的双轴压压强度试验，考察了试件的破坏形态和表面裂缝的走向特征。根据试验结果，分析了极限抗压强度随冻融循环次数和应力比的变化规律，并在此基础上建立了考虑海水冻融影响的双轴压压强度准则。探讨了冻融循环作用后轻骨料混凝土的双轴压压变形性能，包括峰值应变、应力-应变关系随冻融循环次数和应力比的变化规律。研究结果说明，随冻融循环次数的增加各种应力比下的应力-应变关系曲线均逐渐扁平，峰值应力点明显下降并右移，说明混凝土的极限抗压强度逐渐降低。     

临坡条形基础下地基极限承载力多因素影响规律的数值分析

为了系统分析边坡对临坡基础极限承载力的影响,采用控制变量法和FLAC3D有限差分软件,分别针对不同坡顶距、坡角、相对密实度、基底宽度的荷载-位移曲线,研究了极限承载力、极限承载力弱化系数、极限承载力系数的多因素演化规律。结果表明:极限承载力、极限承载力弱化系数、极限承载力系数随坡顶距增加而增大,当坡顶距b与基底宽度B之比大于5时增长趋于停滞,但未达到平地地基数值;地基极限承载力、弱化系数随坡角增加近似线性减小,变化速率基本不受坡顶距的影响;地基极限承载力、极限承载力系数随砂土相对密实度增加而增大,同时受到坡顶距的影响,大坡顶距下随相对密实度的变化速率高于小坡顶距;地基极限承载力受基底宽度的影响程度小于坡顶距,随基底宽度增加小幅度增大,极限承载力系数随基底宽度的增大而减小;地基极限承载力弱化系数对相对密实度、基底宽度不敏感;减小坡角、提高相对密实度与增大坡顶距对极限承载力的提高有类似的效果,单纯通过增大坡顶距仍不能达到接近平地极限承载力的水平,适当地减小坡角、增加相对密实度可增大接近平地地基极限承载力的可能性。研究结果可为临坡工程施工方案选择提供借鉴,对推动临坡地基的工程定量计算具有重要作用。     

竖向条形锚板水平拉拔承载规律试验研究

针对竖向条形锚板的拉拔承载研究存在人为区分浅埋、深埋,且界定标准及对力学模型的对称性认识不统一等问题,为了理清锚板拉拔承载随埋深的演化机理,基于数字照相测量技术对砂土中竖向条形锚板的水平拉拔问题开展模型试验研究,就拉拔极限承载力及板前土体位移变形特性随埋深比的变化规律进行分析。试验研究采用自制试验装置开展了14种埋深比工况下的水平拉拔试验,并获得了相应的荷载位移曲线。试验过程中对板周区域进行拍摄,并通过数字图像分析技术构建拉拔过程中板周土体的位移场。结果表明:中密砂中竖向条形锚板的水平拉拔极限承载力随着埋深比的增加而增大,速率由快趋缓,归一化后的承载力比可用埋深比的二次多项式进行表达。随着埋深比的增大,极限拉拔下板前砂土的位移场形态总体上表现出由非对称逐渐向对称连续变化的规律,并可用上下包络角来反映;上包络角基本不随埋深比发生变化,始终保持在(π/4+φ/2)+π/2左右;下包络角则随着埋深比的增加非线性增大,并最终趋于和上包络角相等,范围介于π/2到(π/4+φ/2)+π/2之间。研究成果可为条形锚板水平极限拉拔力学模型的构建提供新的依据。     

湛江组结构性黏土中桩基竖向承载性状模型试验

利用原位模型试验研究湛江组结构性黏土中桩基在竖向荷载作用下的承载性状。选取材质和桩径相同、入土深度不同的6组模型桩,采用慢速维持荷载法,在湛江组结构性黏土中进行单桩原位竖向承载模型试验,得到了单桩荷载-沉降曲线、单桩轴力沿桩身分布曲线、单桩侧摩阻力沿入土深度分布曲线。结果表明:在竖向荷载作用下,湛江组结构性黏土中模型单桩荷载-沉降曲线均存在显著陡降,极限状态拐点明显,竖向极限承载力随着长径比的增加而增大;在相同荷载作用下,随着长径比的增加,桩顶沉降逐渐减小且减小趋势逐渐变缓,在较大荷载作用下超长桩荷载-沉降曲线中桩顶沉降的减小速率几乎为零,存在有效桩长;在同级桩顶荷载作用下,单桩桩端阻力占总桩顶荷载的比例随着长径比的增加而逐渐变小,由最大29.8%减小为0.8%;不同入土深度的单桩在极限荷载作用下的桩侧极限摩阻力变化不大,均稳定在40 k Pa左右。     

Theoretical and practical identifiability of a reduced order model in an activated sludge process doing nitrification and denitrification

This paper deals with the structural identifiability and the identification of the parameters of a reduced order model used for control of a single reactor activated sludge process doing nitrification and denitrification. This reduced order model is splitted into two submodels, one 3-dimensional state submodel in aerobic conditions and one 2-dimensional state submodel in anoxic conditions. The identifiability analysis is based on on-line oxygen and nitrate concentrations data. It has been shown that the reduced order model is structurally identifiable. The parameter identification has been carried out by using the simplex method of Neider and Mead. Simulation results performed over a range of six hours (two aerobic/anoxic cycles), show that there exists a good fit between the simulated solution and the actual behavior of a lab scale pilot plant.     

上钢下混组合桩水平承载性能影响因素分析

为研究不同因素对上钢下混组合桩水平承载性能影响,采用有限元软件ABAQUS,计算分析不同接桩深度、桩径、联接段参数的上钢下混组合桩在水平荷载作用下的桩身水平位移、弯矩、应力分布以及极限承载力。研究结果表明,组合桩接桩深度是影响上钢下混组合桩水平承载性能的主要因素,组合桩桩径、联段刚度和长度的影响相对较小,提出上钢下混组合桩接桩深度不小于10D,可确保组合桩的水平承载性能不低于同条件钢管桩的结论,为上钢下混组合桩的工程应用提供了技术支撑。