颗粒粒径分布对全散射法测量颗粒质量浓度的影响

燃煤电厂烟尘排放是造成环境污染最主要的因素之一,实现电厂排放烟尘浓度的在线监测显得尤为重要。以光全散射法为理论基础,运用MATLAB编程,得到消光系数与粒径、复折射率的关系以及颗粒浓度与消光曲线的关系;在实验室搭建粉尘浓度监测台架,用0.81和2.1μm这2种聚苯乙烯标准颗粒在液相介质中对台架测试结果进行标定;而后选取3种粒径分布不同的二氧化硅球形颗粒进行测量,测量结果表明,样品中无量纲尺寸因子α30的颗粒所占的比例越高,浓度测量的误差越大。     

角散射法运行中油品颗粒度在线测量装置研究

对角散射方法用于在线测量运行中油品颗粒度技术及相应装置展开研究,依据Mie散射理论,利用激光光源、光学组件以及光电倍增管搭建了一套90°方向采光的异轴采光装置,并采用宽口径、短光程特殊结构光学比色皿,以同时满足单颗粒散射和实时检测需要.在实验室条件下,利用国家标准物质聚苯乙烯溶液和GWB(E) 120017油中颗粒国家标准物质对装置的测量准确度进行检验,检验结果证实,装置测量准确度较高.在湖南五凌电力公司洪江电厂进行为期一个月的在线测量性能测试,通过与湖南电力科学院、五凌电力中试所测试结果对比证实,装置具有较好的准确度和稳定性,可用于油品颗粒度在线监测.     

散射式水下浊度测量方法的研究

以国际标准的散射式测量方法为浊度测量手段,采用850 nm近红外单色光作为入射光测量水体的浊度,实现了水下连续在线测量.分析了散射式浊度测量原理及其测量系统的构成,通过对不同浊度的水体进行了测量实验,测量结果表明该测量方法实时性好、稳定性和准确性高,可以有效地测量水体的浊度值,既适用于实验室内测量也适用于野外测量,具有广泛的应用前景.     

电厂调速器油系统颗粒度的光散射法在线监测

随着智能化电厂建设的推进,机组状态监测的重要性日益凸显。从电厂汽轮机油颗粒度的在线监测入手,采用光散射法原理,在实验室自主研发颗粒度仪,并进行标定和验证。在洪江水电厂2号机组调速器油系统应用后,发现并解决了一起油污染隐患事故,表明监测的数据能够反映机组的运行工况。通过比较得出该颗粒度仪的在线监测结果与HACH 8011+型和PAMAS SBSS型颗粒计数器基本一致,证明光散射法精度高,适用于在线监测汽轮机油颗粒度,为机组从计划性检修转向状态检修提供了条件。所开发的颗粒度仪具有成本低和稳定性好的特点。     

发供电技术信息

光散射平均值法在线监测颗粒排放物浓度的研究、自适应暂态计算在继电保护分析中的应用、基于小波变换的选择性发电机100％定子单相接地保护方案、一种用于高压混合有源电力滤波器的复合控制方法     

纳米颗粒的粒径测定

介绍了纳米颗粒粒径大小的常见测量方法和技术,这些方法包括电镜法、X-射线衍射法、激光粒度分析法、沉降法、X-射线小角散射等,指出了它们的应用范围并对这些方法的优缺点进行了讨论.     

应用近场线散射技术测量天线辐射方向图

本文描述了天线方向图的一种测量方法。当一根细金属导线在天线口径面上移动时,馈源处的反射系数会产生变化。如果天线口径场分布是保分的,那么它的反射系数的变化就与导线位置处积分口径场的平方成比例。以金属导线散射信号引起的反射系数变化的平方根作为导线位置处的函数,可得到积分口径场,由此可推导出天线远场辐射方向图。这种测量系统现已建成,其测量结果与传统的远场测量结果相比较一致性很好。这种测量方法能使我们快速     

日盲紫外光霾粒子光散射测量方法研究

针对光散射粒子测量方法中测量结果受到外界杂散光干扰这一问题,提出将日盲紫外光应用于光散射粒子测量方法中。利用Mie散射理论仿真了日盲紫外光不同粒径粒子的散射光分布函数,结果表明,日盲紫外光对粒径较小的粒子散射特性良好,能够应用于光散射粒子测量方法之中。利用T矩阵方法计算了日盲紫外光椭球粒子的散射特性,结果表明,在日盲紫外光248 nm处,椭球粒子的消光截面相比等效球形粒子偏小2.82%,散射截面偏小1.95%。最后分析了椭球粒子形变参数与复折射率对其散射相函数的影响,这些分析为光散射粒子测量方法提供了一定的理论依据。     

基于光子相关光谱法动态光散射测量系统研究

设计了一种动态光散射测量系统,即无光纤参与的动态光散射系统,其目的是研制适用颗粒浓度范围大、测量颗粒尺寸准确、易于操作、尺寸紧凑、适于在线检测、价格相对低廉的纳米(亚微米)颗粒粒度仪.对纳米颗粒悬浮溶液的单分散体系和双分散体系均进行了讨论,并对纳米颗粒粒度的反演运算进行详细阐述,最后对该系统的测量准确性进行了研究.试验结果表明,我们初步搭建了较为合理的基于PCS的DLS测量系统,它对纳米颗粒粒度分布,主要是对纳米颗粒悬浮溶液的单分散体系和双分散体系实现了准确的测量.     

冶炼车间大气散射模型图像去烟尘算法

针对冶炼车间中大量烟尘、水雾等悬浮颗粒造成的图像降质等问题,本文提出冶炼车间大气散射模型图像去烟尘算法。为更好地估计真实大气光值,通过简单线性迭代聚类分割算法求取初始大气光值,并采用快速引导滤波对初始大气光值进行精细化处理,同时利用自适应伽马函数对大气光和原始烟尘图像进行修正,分别得到最终大气光和优化后的烟尘图像。通过优化的颜色衰减先验模型估计出透射率,最后根据大气散射模型恢复无烟尘图像。实验结果表明,该算法可降低图像中的烟尘浓度,减少图像细节损失,使方均误差平均下降66.2%,峰值信噪比平均提高30.5%,结构相似度平均提高48.6%。     

基于DSP的声纳电功率测量系统

正交双通道处理技术保留了信号的幅度和相位信息,用这种方法可以实现无理论误差地测量音频正弦信号有效功率。为了实现对声纳发射有效电功率的测量,基于此技术设计了声纳发射有效电功率测量系统,系统采用专用数字信号处理器DSP和单片机AT89C51构成双微处理器工作方式,数字信号处理器用来实现各种算法和完成数据运算,单片机AT89C51用来实现系统控制。通过实际测量,此系统满足设计要求并在实际中得到应用。     

A study of radar cross-section measurements in an anechoic chamber

Radar cross-section measurement techniques in a relatively small anechoic chamber are discussed in this paper. The proper configuration of the measurement system and antenna/target setting for securing a wide dynamic measurement range is studied. A quasi-monostatic configuration is recommended here instead of a monostatic one, and various suggestions are made for reducing isolation error and background noise, along with calibration techniques and antenna settings. Measurement examples are shown for a conducting plate and parallel plane waveguide cavities. These results are then compared with those derived theoretically by the geometrical theory of diffraction and the Wiener-Hopf technique. Good agreement is obtained between them, and the validity of our measurements is confirmed. © 1998 Scripta Technica, Electr Eng Jpn, 123(1): 8–14, 1998     

Permittivity measurement of disk and annular dielectric samples using coaxial transmission line fixtures. part II: experimentation and accuracy analyses

An improved permittivity measurement technique for dielectric disks involving S-parameter measurement of a two-port coaxial transmission line fixture is presented. The previous form of the method suffers from variation of the retrieved permittivity with frequency, which leads to inaccuracies that may be severe at some frequencies. An extension of the method that reduces these errors is devised. In addition, an independently developed new technique for measuring the permittivity of annular samples via quadratic curve fitting is presented. This technique also involves S-parameter measurement of a coaxial fixture and requires measurement of only three known materials (one of them may be free space, in which case the requirement is reduced to only two solid dielectrics). The permittivity of any unknown dielectric may subsequently be determined with high accuracy over a wide frequency range. The method is based on the premise that the variation of the reflection characteristics of the two-port coaxial transmission line fixture with the permittivity of the sample displays a strongly quadratic behaviour. This paper constitutes the second of two parts of this work. Part I, also appearing in this issue, presents the theoretical formulation for the moment method mode-matching treatment of the coaxial fixture for treating annular samples. In the present paper, the measurement techniques are described, and numerical simulations of the experimental procedure based on the theory of Part I are presented. In addition, comparative results of accuracy for these two approaches are given. Sensitivity analyses are also presented, along with preliminary experimental results.     

电网相量同步测量技术及应用

为动态监测全网,分析了常规电网监测系统的缺陷,介绍了基于GPS(全球卫星定位系统)和现代通信技术的全新电网监测和控制手段——全网相量同步动态监测技术和系统,包括该系统中相量测量装置的设计原则、核心算法、系统通信方式的选择等关键技术及其应用前景,重点阐述了该技术在系统动态过程监测、不稳定预测、系统状态估计和失步保护与故障定位等方面的应用。基于电网相量同步测量技术的动态监测系统,改变了常规电网监测系统的状态估计和控制方式,提供了直接电网监测和控制的依据,提高了整个系统的可观性。调度员可实时观察到全网各节点间相角差的变化情况,并作出调度和稳定控制策略。它在电网监测和安全稳定控制上开辟了一个新的领域,在电力系统的动态分析中有很大应用前景。     

考虑声波折射补偿的海底热液口声学原位测温方法

介绍了海底热液口温度场原位声学测量方法,进行了海底非均匀温度场中声波折射传播路径研究,并建立了声波传播路径的数学模型,利用COMSOLMultiphysics软件进行了声波传播路径的数值求解.在云南省龙陵县境内的茄子上水库的湖底热泉进行了实验研究,准确地还原出温度场.考虑了声波折射补偿,提高了声波飞渡时间估计精度,并对声波路径弯曲补偿前后重建出的温度场进行最大绝对误差、最大相对误差和均方根误差分析.实验表明:对声波信号传播路径由曲线变直线进行补偿,可提高温度场原位测量的精确性.     

On the suitability of GO/UTD modelling of microwave propagation in indoor environments

The main aim of this paper is to show the suitability of the geometrical optics and uniform theory of diffraction (GO/UTD) approach for modelling microwave propagation in indoor environments. Implementation details for an efficient method based on a combination of image theory and the binary space partitioning (BSP) algorithm to perform ray tracing are presented. The efficiency of the method allows a full three‐dimensional implementation of the GO/UTD approach. An extensive measurement champaign has been carried out in order to analyse the degree of accuracy achievable by the method. Some of these comparisons between measured and simulated data are presented, and a quantitative analysis of errors is made. The analysis reveals that the degree of precision in the calculation of the signal levels allows not only the signal mean level but also its statistics to be estimated accurately. The error in the mean level of the signal is less than 2 dB in the majority of cases, a maximum error of 3.6 dB having been obtained. The statistics of the signal fit Rice distributions very closely with different values of the rician parameter K. Finally, a brief study of the influence of the number of ray mechanisms considered (reflected, double reflected, etc.) on the accuracy and calculation times is also presented. Copyright © 2001 John Wiley & Sons, Ltd.     

VXI测试设备检定测试方法

针对VXI测试设备的被测对象及其精度,研究其检定测试方法.并根据该方法,研制了基于PXI总线的VXI测试设备的检定测试装置.文中分PXI测试系统、信号转接箱和检定流程三部分介绍检定测试装置的系统设计,进行详细说明;文中还介绍检定软件的设计,包括软件的运行环境、软件开发平台、软面板设计、软件体系结构、软件详细流程;此外,还总结解决的关键技术,包括基于闭环反馈测量的高精度信号变换技术、智能多路信号生成技术、硬件跟随信号同步采样技术.     

A new adaptive technique for on-line partial discharge monitoring

The insulation system of HV apparatus deteriorates due to partial discharges (PD). PD tests are carried out successfully in shielded laboratories to verify the insulation quality and to rectify defects left during the manufacturing process. A variety of techniques exists for this purpose. It is also desired to monitor the insulation when equipment is in operation. Unfortunately, the performance of PD test equipment is adversely affected by interference signals. The sinusoidal signals of low and high frequency, due to their correlation, make the measurement difficult and sometimes even impossible. This paper describes the design of an adaptive digital filtering technique and its successful application to the on-line/on-site detection of PD current pulses generated in HV insulation in the presence of sinusoidal noise signals. The technique is based on Wiener optimal filtering theory and its characteristics are investigated. The adaptive filter of this system has a time-varying response and is self-tuning to each low and high frequency noise component. The filter remains active until the signal-to-noise ratio is significantly increased and it can be used for weak PD pulse integration. Theoretical background of the technique and the results of laboratory and field tests are presented     

基于相位差校正法的高精度电力谐波检测

研究了基于FFT理论的电力谐波检测原理,提出一种基于相位差校正法的高精度电力谐波检测方法.文章首先从FFT的基本理论出发,推导出FFT频谱相位差校正的理论公式,给出利用该方法检测电力谐波的操作步骤.接着利用MATLAB分别仿真了基于该方法和直接FFT法的电力谐波检测精度.结果表明,该方法能够明显的提高检测精度.可以满足实际的电力谐波检测.     

An adaptive PMU based fault detection/location technique fortransmission lines. II. PMU implementation and performance evaluation

Part I of this paper set sets forth theory and algorithms for adaptive fault detection/location technique, which is based on phasor measurement unit (PMU). This paper is Part II of this paper set, A new timing device named “Global Synchronism Clock Generator, GSCG” including its hardware and software design is described in this paper, Experimental results show that the synchronized error of rising edge between the two GSCGs clock is well within 1 ps when the clock frequency is below 2.499 MHz. The measurement results between Chung-Jeng and Chang-Te 161 kV substations of Taiwan Power company by PMU equipped with GSCG is presented and the accuracy for estimating parameters of line is verified. The new developed DFT based method (termed as smart discrete Fourier transform, SDFT) and line parameter estimation algorithm are combined with PMU configuration to form the adaptive fault detector/locator system. Simulation results have shown that SDFT method can extract exact phasors in the presence of frequency deviation and harmonics, The parameter estimation algorithm can also trace exact parameters very well, The SDFT method and parameter estimation algorithm can achieve accuracies of up to 99.999% and 99.99%, respectively. The EMTP is used to simulate a 345 kV transmission line of Taipower System. Results have shown that the proposed technique yields correct results independent of fault types and is insensitive to the variation of source impedance, fault impedance and line loading. The accuracy of fault location estimation achieved can be up to 99.9% for many simulated cases, The proposed technique will be very suitable for implementation in an integrated digital protection and control system for transmission substations