二次实际负载对电流互感器误差的影响

电能计量误差由电能表误差、互感器合成误差、电压互感器二次导线压降引起误差的代数和;实际运行的二次负载阻抗的大小直接影响电流互感器的误差;分析和讨论实际二次负载阻抗对电流互感器误差的影响。     

变压器外特性的研究

电力系统的用电负载是经常变化的,这种变化对变压器的运行状况是有影响的。主要研究负载变化对变压器二次侧输出电压的影响,即外特性的研究。     

化学沉淀法制备S-FeS/介孔碳复合材料及其电化学性能

为提高锂硫电池的循环性能,采用化学沉淀法制备了负载有FeS的介孔碳(MC)复合材料FeS/MC,通过热复合获得了负载S的MC复合材料S/MC和负载S、FeS的MC复合材料S-FeS/MC。FeS/MC的SEM照片表明,FeS可充填MC表面的孔洞。N2吸脱附等温线表明,负载FeS后,MC的比表面积大幅下降,但平均孔径增大。XRD谱图表明,当负载FeS的含量达到20wt%时,出现了Fe3S4晶相。电化学性能测试结果表明:负载于MC中的FeS本身没有电化学活性,但它对多硫离子的氧化还原过程有催化作用,提高了电极的可逆性;S-FeS/MC的二次放电比容量保持率高于S/MC的比容量保持率,表现出较轻的"飞梭效应";S-FeS/MC的二次放电比容量为1 108.8mA·h/g,50次循环容量保持率为43.7%,高于S/MC的容量保持率,表现出较好的循环性能。     

提高实际负载下检定电流互感器误差的准确性

本文对一直被忽视的“电流互感器实际二次负载影响误差的情况”进行了测试 ,并对反映出一些问题进行了分析 ,并提出了改进措施     

电压互感器二次回路导线截面计算公式

针对电压互感器二次回路负荷为△、Ｖ、Ｙ。形接线情况。考虑二次回路接触电阻因素，推导出了电压互感器二次回路导线截面计算公式，对于△形负载三相不对称情况，该公式同样适用。按计算公式推出的导线截面，一航能满足机械的要求。     

检流计内阻及灵敏度的测量

灵敏度和内阻是灵敏检流计非常重要的两个特征参数,采用二次分压电路,分析并测量了与检流计串联的电阻和负载电路电压的关系数据并利用最小二乘法得到斜率及截距,测定出灵敏检流计的灵敏度及内阻。     

电流互感器在实际负载下的在线检定

目前我国电力网络用于配电装置的电流互感器多为LMK-0．5型，由于国家标准明确规定了保证其准确度的二次负载上、下限，因此，在检定使用中的电流互感器时，也常常是在实验室内或现场就额定负载的上、下限进行检定，而忽视了运行中的电流互感器所带的实际负载，     

数字钳形表在二次电流回路中的应用

在保护齐全的变配电设备中,由于电流互感器（以下简称ＣＴ）二次电流回路负载多、接线复杂,而设备运行后,二次侧又严禁开路,这样,试运前的大电流整组试验和试运后的复校,用“串表法”既有危险又不方便。笔者通过多年实践摸索出一套“数字钳形表在二次电流回路中的应...     

NO2浓度对水泥基材料负载纳米TiO2光催化性能的影响

研究鉴于汽车尾气排放后首先与路面材料接触的事实,探讨路面材料负载光催化剂实现尾气二次净化的目的.针对路面水泥基材料负载纳米TiO2光催化氧化汽车尾气中的氮氧化物,首重研究模拟气源NO2的浓度对催化反应的影响.试验和分析表明,水泥基材料负载纳米TiO2光催化氧化NO2浓度提高呈线性下降:水泥基材料负载纳米TiO2光催化反应速率随NO2浓度提高而加快;若载体具有吸附被光催化氧化气体的能力,可加快负载TiO2的光催化反应.     

变电站蓄电池运行常见故障原因分析及措施

在变电站中,直流系统是核心,为断路器分、合闸及二次回路中的继电保护、仪表和事故照明等提供能源。而在直流系统中提供能源的主要是蓄电池,蓄电池相当于变电站整个二次系统的心脏,为二次系统的正常运行提供动力。因此,蓄电池的稳定性和在放电过程中能提供给负载的实际容量对确保电力设备的安全运行具有十分重要的意义。     

Estimation of Parameters of Universal Distribution of Moments of Failure of Products

A method is proposed for estimating the parameters of a mixture of exponential and Weibull distributions for which the accuracy of preliminary estimates obtained by graphical analysis is refined in accordance with the criterion of maximum likelihood. The efficiency of the proposed method is supported by the results of statistical modeling.     

Evaluation of optical properties of highly scattering media by moments of distributions of times of flight of photons

A novel method for the determination of the optical properties of tissue from time-domain measurements is presented. The data analysis is based on the evaluation of the first moment and the second centralized moment, i.e., the mean time of flight and the variance of the measured distribution of times of flight (DTOF) of photons injected by short (picosecond) laser pulses. Analytical expressions are derived for calculation of absorption and of reduced scattering coefficients from these moments by application of diffusion theory for infinite and semi-infinite homogeneous media. The proposed method was tested on experimental data obtained with phantoms, and results for absorption and reduced scattering coefficients obtained by the proposed method are compared with those obtained by fitting of the same data with analytical solutions of the diffusion equation. Furthermore, the accuracy of the moment analysis was investigated for a range of integration limits of the DTOF. The moment analysis may serve as a comparatively fast method for evaluating optical properties with sufficient accuracy and can be used, e.g., for on-line monitoring of optical properties of biological tissue.     

Analysis of the rate of propagation of the wave of change of boiling modes

An approximate analytical expression is derived for the velocity of the front of the wave of change of boiling modes on a rod and on a plate. The impact of the Thomson effect and of the heater orientation in the gravity field is included. Adequate agreement is demonstrated between the derived relations and experimental data.     

Estimation of potentialities of methods of summation of direct measurement errors

Conventional methods for summation of direct measurement errors are considered. Conditions under which these methods provide consistent results are stated. It is proposed to utilize for characteristic of the total error, its interval estimator or the half-sum of the value obtained by adding up its arithmetic and geometric random errors.Translated from Izmeritel'naya Tekhnika, No. 4, pp. 10–12, April, 1995.     

空压机轴承箱蜗壳温度探头油封改造

由于空压机进气侧轴承箱蜗壳温度探头密封效果不好,使空压机及其后续管道受到油污染。后将温度探头的O形圈密封改为骨架油封,杜绝了轴承箱漏油问题。文章简介空压机的结构和技术参数,详细介绍了骨架油封的制作和优点。     

Characteristics of mechanical properties of materials in studies of conditions of attainment of marginal states

It is shown that conditions of attainment of marginal states in the material of structural components are formulated on the basis of analysis of force and deformation criteria of formation and development of destruction. The parameters of these criteria are data on types of structural materials, standard and special characteristics of their mechanical properties, structural forms of considered elements of the equipment, and their operating stress loading. In this case, the construction of a system of state equations for describing interrelation of current damage, external actions, and responses to them is based on the concept of calculating variations in properties of materials at all stages of the design life cycle.     

Determination of parameters of microstructural inhomogeneity of deformation of metals by the method of modeling

The article suggests a method of evaluating the microstructural inhomogeneity of deformation of metals by modeling. The method includes the measurement of deformations of metal according to meshes of a dividing grid with small base and the calculation of the distribution parameters of microdeformations in model representation. It is shown that the modeling method makes it possible objectively to evaluate the microinhomogeneity of deformation of metals independently of the chosen mesh size of the dividing grid. New structural characteristics are introduced: the base and wave of variation expressing the degree of crumbling or amalgamation of metal grains by inhomogeneity of deformation.Translated from Problemy Prochnosti, No. 7, pp. 40–44, July, 1991.     

水三相点复现的不确定度评定

水三相点是开尔文热力学温度的唯一基准点，也是ITS-90国际温标重要的定义固定点。因此，水三相点不确定度分析对整个温标的建立、温度量值传递起着至关重要的作用。近3年来，中国计量科学研究院研制出一系列高质量的水三相点容器，加强了水三相点的研究，为不确定度的分析提供了更为可靠的实验依据。同时，不确定度的分析也是客观评价新研制容器性能的一个重要指标。因此，根据实验结果对新研制容器所复现的水三相点进行了不确定度评定。评定结果表明，其扩展不确定度为0．16mK(k=2．69，P=0．99)。