THE STUDY ON MEASURING TECHNIQUE OF PARTIAL DISCHARGE IN GAS INSULATED SWITCHGEAR USING ULTRA HIGH FREQUENCY METHOD WITH EXTERNAL SENSORS

Objective In order to find early latent faults and prevent catastrophic failures, diagnosis of insulation condition by measuring technique of partial discharge(PD) in gas insulated switchgear (GIS) is applied in this paper, which is one of the most basic ways for diagnosis of insulation condition. Methods Ultra high frequency(UHF) PD detection method by using internal sensors has been proved efficient, because it may avoid the disturbance of corona, but the sensor installation of this method will be limited by the structure and operation condition of GIS. There are some of electromagnetic (E-M) waves leak from the place of insulation spacer, therefore, the external sensors UHF measuring PD technique is applied, which isn't limited by the operation condition of GIS. Results This paper analyzes propagated electromagnetic (E-M) waves of partial discharge pulse excited by using the finite-difference time-domain (FDTD) method. The signal collected at the outer point is more complex than that of the inner point, and the signals' amplitude of outer is about half of the inner, because it propagates through spacer and insulation slot. Set up UHF PD measuring system. The typical PD in 252kV GIS bus bar was measured using PD detection UHF technique with external sensors. Finally, compare the results of UHF measuring technique using external sensors with the results of FDTD method simulation and the traditional IEC60270 method detection. Conclusion The results of experiment shows that the UHF technique can realize the diagnosis of insulation condition, the results of FDTD method simulation and the result UHF method detection can demonstrate each other, which gives references to further researches and application for UHF PD measuring technique.

MEASURING PRECISION OF INDUCED POLARIZATION METHOD

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Application of Uniform Experimental Design in Optimizing Excitation Parameters for Magnetic Frequency Mixing Measurements

Excitation parameter preferences are key factors a ecting the performance of magnetic frequency mixing detection.A uniform experimental design method was used to analyze this influence.Using fuzzy theory,a comprehensive model is established for evaluating the e ect of magnetic frequency mixing.A polynomial is selected as the regression function to express explicitly the correlation between the excitation parameters and the frequency-mixing e ect.The excitation parameters were then optimized using genetic algorithm.Magnetic frequency mixing experiments were conducted to measure the surface hardness of some ferromagnetic materials.Frequency mixing is further enhanced under the optimal settings,resulting in an improvement in the measurement sensitivity.The results of this study support the application of the magnetic frequency mixing technique in non-destructive testing.

Injection transient study using a two-frequency bunch length measurement system at the SSRF

The bunch length can be measured by comparison of two frequency components of a synchrotron beam signal.An online bunch length measurement system has been implemented based on this method.Working frequencies of 3 GHz and 500 MHz were selected,and the raw data was acquired by digital oscilloscope and was resampled and analyzed using the MATLAB software platform at bunch-by-bunch rate.The constructed system was employed to study the bunch length synchronous oscillation phenomenon during injection.The beam experiments demonstrated a time resolution of less than 0.5 ps.

Experimental Assessment of the Battery Lifetime in WSN Based on the <i>Duty</i>-<i>Cycle</i><i>Current</i><i>Average</i>Method

A great amount of work addressed methods for predicting the battery lifetime in wireless sensor systems. In spite of these efforts, the reported experimental results demonstrate that the duty-cycle current average method, which is widely used to this aim, fails in accurately estimating the battery life time of most of the presented wireless sensor system applications. The aim of this paper is to experimentally assess the duty-cycle current average method in order to give more effective insight on the effectiveness of the method. An electronic metering system, based on a dedicated PCB, has been designed and developed to experimentally measure node current consumption profiles and charge extracted from the battery in two selected case studies. A battery lifetime measurement (during 30 days) has been carried out. Experimental results have been assessed and compared with estimations given by using the duty-cycle current average method. Based on the measurement results, we show that the assumptions on which the method is based do not hold in real operating cases. The rationality of the duty-cycle current average method needs reconsidering.

Greenhouse gas emission analysis and measurement for urban rail transit: A review of research progress and prospects

Rail transit plays a key role in mitigating transportation system carbon emissions.Accurate measurement of urban rail transit carbon emission can help quantify the contribution of urban rail transit towards urban transportation carbon emission reduction.Since the whole life cycle of urban rail transit carbon emission measurement involves a wide range of aspects,a systematic framework model is required for analysis.This research reviews the existing studies on carbon emission of urban rail transit.First,the characteristics of urban rail transit carbon emission were determined and the complexity of carbon emission measurement was analyzed.Then,the urban rail transit carbon emission measurement models were compared and analyzed in terms of the selection of research boundaries,the types of greenhouse gas(GHG)emissions calculation,and the accuracy of the measurement.Following that,an intelligent station was introduced to analyze the practical application of digital collaboration technology and energy-saving and carbon-reducing system platforms for rail transit.Finally,the urgent problems and future research directions at this stage were discussed.This research presents the necessity of establishing a dynamic carbon emission factor library and the important development trend of system integration of carbon emission measurement and digital system technology.

Low frequency characteristic parameters measurement of vented-box loudspeaker system using total least squares method

The interrelationship between the ARMA model parameters of a vented-box loud-speaker system and lowthequency characteristic parameters is analysed in this paper. These AANA model parameters are deterndned by the total least squares (TLS) method. Therefore, we can measure in the timedomain the fow frequency characteristic parameters of a vented-box loudspeaker system, its impendance curvs and low-frquency response curves. These measured results show a satisfactory agreement with the values obtained by the frequency-domain measurement.

Probing the minigap in topological insulator-based Josephson junctions under radio frequency irradiation

Recently,a contact-resistance-measurement method was developed to detect the minigap,hence the Andreev bound states(ABSs),in Josephson junctions constructed on the surface of three-dimensional topological insulators(3D TIs).In this work,we further generalize that method to the circumstance with radio frequency(rf)irradiation.We find that with the increase of the rf power,the measured minigap becomes broadened and extends to higher energies in a way similar to the rf power dependence of the outer border of the Shapiro step region.We show that the corresponding data of contact resistance under rf irradiation can be well interpreted by using the resistively shunted Josephson junction(RSJ)model and the Blonder–Tinkham–Klapwijk(BTK)theory.Our findings could be useful when using the contact-resistancemeasurement method to study the Majorana-related physics in topological insulator-based Josephson junctions under rf irradiation.

Analysis of prospecting polymetallic metallogenic belts by comprehensive geophysical method

This paper is based on the analysis and research on the silver-lead-zinc polymetallic ore in New Ballyhoo Banner in southern Manzhouli of Inner Mongolia.Because metal mineralization brings rock formations,the geophysical features such as low resistivity,high polarization rate and uneven distribution of magnetization,the comprehensive geophysical methods are adopted including high-precision magnetic measurement,high-power induced polarization,IP field middle gradient and controlled source audio-frequency magnetotellurics.In the survey work of multi-metal ore deposits,from surface sweeping to single point measurement,and from single point to section going deeper layer by layer,the resolution of measurement is continuously improved,and various geophysical methods support and complement each other,so explorers can successfully predict the direction,scale and volume of the metallogenic belts in conjunction with geochemical exploration,geological survey and drilling.It has provided a strong basis for completing the exploration task of predicting the reserve volume of ore bodies.The research conclusions of this exploration case have thus a high reference value in the same type of exploration work.

样品尺寸对脉冲穿透法声速测量误差的影响

岩心的声速测量能够提供关键的储层地质信息,对储层评价和地质模型构建具有实际应用价值。脉冲穿透法是一种常用的声速测量方法,但它要求样品尺寸远大于波长(约10倍)。当特殊场景如需在测井信号主频8~20 kHz下测量样品声速时,被测样品长达数米,不仅制备困难,还存在声波信号衰减大的问题。关于试样尺寸能否缩小或能缩小到什么程度的定量研究很少见到公开报道。该文将数值模拟和实验测量相结合,系统定量地研究了圆柱状样品长度及直径与波长之间的比值对脉冲穿透法声速测量精度的影响。研究表明:为确保脉冲穿透法声速测量的准确性,建议样品沿传播方向上的长度不低于4倍声波波长,横向尺寸不低于2倍波长。研究结果突破了传统脉冲穿透法要求样品尺寸远大于波长的限制,为优化声速测量方法和提高测量精度提供了理论支持。

航空发动机全生命周期碳排放计量方法研究

航空产业是碳排放八大重点行业之一,航空产业的碳排放主要受航空发动机碳排放的影响,因此亟需开展航空发动机碳排放计量方法研究。以生命周期评价作为航空发动机碳足迹的量化方法,将航空发动机全生命周期碳排放分为燃料周期碳排放与材料周期碳排放,并分别进行统计;将航空发动机系统边界进行划分,对各个阶段进行数据收集,并对数据做出要求,得到一套相对完整的航空发动机碳排放计量方法。本文得到的方法可以从生命周期的角度全面评估航空发动机碳排放,能够为航空发动机全生命周期碳排放计量提供指引,从燃料角度与材料角度为减排提供理论基础。

基于标准场法的低频电场计量技术探讨

为了实现低频电场测量仪的校准,探讨了基于标准场法的低频电场计量技术。描述了低频电场测量仪的结构和工作原理,分析了应用平行板产生可计算标准电场的方法,研究构建了校准系统。应用该系统进行了校准测量实验,分析了测量误差来源,评估了测量结果的不确定度。将实验结果与应用横电磁波室法的测量结果作了比较,数据表明该校准系统的测量结果合理,满足低频电场测量仪的校准要求。

增强微分偏振调制测距算法实现

针对偏振调制测距系统直接测量光强极小值分辨率低且扫频速度慢的问题,提出了基于增强微分的偏振测距算法。首先,根据测距原理分析了频率测量对距离测量精度的影响;然后,利用采样信号的对称特性提出增强微分算法,进行算法的原理、步骤和关键参数分析,获得最佳参数组合范围;最后,搭建了偏振调制测距系统,验证提出的参数组合,并与拟合微分法进行测距精度和速度对比实验。实验结果表明:提出的方法相比于拟合微分法测距重复性由58μm提高至6.8μm,平均绝对测距精度提升至0.207mm,扫频步数由1100个减少至250个,测量时间减少至2s,精度和速度得到有效提升。

长距离场地自行车运动员骑行中的迎风面积研究

研究目的:在长距离场地自行车比赛中,当运动员输出功率相近时,空气阻力是影响成绩的主要因素,而运动员迎风面积的测定是空气阻力研究中的关键因素。为精确测定不同形态运动员在不同骑行姿态时的迎风面积,研究采用平面测量法进行测试。研究方法:使用数码相机采集运动员的正面图像信息,利用CAD网格矫正图像畸变,得到了4名运动员不同躯干角度的迎风面积结果。研究结果:(1)迎风面积值在0.32~0.35 m~2之间,其中运动员2在8°和16°时值最大,躯干特征参数占比最大;(2)迎风面积在躯干面积较大时对骑行姿态变化较为敏感,并分析得到了迎风面积的估算模型,可为教练员和运动员的训练与比赛提供较为准确的数据参考。

一种基于圆周运动轨迹方程的电力系统基波频率测量方法

随着新能源的大规模接入,系统惯量降低,电力系统的频率波动变得剧烈,增加了频率准确测量的难度,而频率的测量精度直接关系着电力系统各类基于频率控制应用的有效性。因此,该文从圆周运动角度,提出了一种新颖的频率精确测量方法。该方法建立了电力系统电压信号正弦变化的旋转相量圆周运动表征模型,基于匀速圆周运动和变速圆周运动的轨迹运动方程,推导了旋转相量及其导数与系统频率之间的函数关系;利用二次多项式拟合电压信号动态变化的幅值和相角,提出了基于最小二乘法的旋转相量及其导数求解方法,进一步,提出了基于频率网格化的迭代优化方法,消除了频率偏移对算法的影响。仿真和硬件测试表明,所提算法在频率偏移、线性和非线性变化条件下均能准确地测量基波频率。

基于相参积累激光扫频干涉液位测量方法研究

工业生产中,容器内液位高度的控制是生产运输过程中对确保设备正常运行和维护人员生命安全具有重要意义。本文提出采用激光扫频干涉测量系统对液位进行测量,该方法具有诸多优势,如测量范围大、非接触式测量、响应速度快和操作便捷等。由于液体对红外光的吸收率相对较高,导致测量系统采集到的回光信号非常微弱,同时信噪比也不够理想。为解决此问题,本文引入相参积累方法,并将其与测量系统相结合,以提高液位检测的精准度。在信号的各个周期中,信号携带的有效信息保持一致,噪声信息是则随机的,因此通过相参积累方法处理后,不仅可以增强信号强度,还可以提升信噪比。再通过扩相频率采样法进行信号的非线性校正,最后对数据进行处理就,即可以获得液位信息。实验结果表明,相参积累方法对增加信号强度与信噪比有显著效果,为解决低信噪比下提升测量精度问题提供了思路。

射频热疗设备校准方法的研究探索

射频热疗设备结果的准确与否对肿瘤的治疗效果有着直接的影响,为尽可能避免相关不良事件的发生,本文研究其校准方法。通过射频热疗设备工作原理的研究,对关键参数的量值溯源体系的搭建进行可行性分析,确定主要参数的计量性能及校准方法并验证。射频热疗设备校准方法的研究,为《射频热疗设备校准规范》的编写提供助力,促进射频热疗设备量值溯源和标准化,有助于加强射频热疗设备在使用过程的监管。

HDPE管与拉索接触相对长度对索力的影响

为了准确测量平行钢绞线拉索内部接触情况对索力的影响,对其截面特性及索力力学关系进行分析,研究内部接触的不同影响机理。施工中为避免钢绞线的锈蚀,采取在拉索上套HDPE管的防护措施,对此进行试验验证。实验结果显示,HDPE管的自重是拉索的重要影响因素,当HDPE管与拉索接触时,拉索振动行为表现出整体性及独立性,导致各部分振动发生耦合,耦合振动具有一致性,为通过振动频率法测量总索力提供了理论基础,但在非接触区域测得的频率并非拉索的真实频率,因此对于非常规的平行钢绞线拉索,当HDPE管与拉索索股的接触耦合不完好时,测得的频率误差超出规范要求且不能忽视。应用修正公式计算索力,可满足工程需求,提高索力的计算精度。

基于小波去噪和时频分析的智能电表量测数据挖掘研究

为提升智能电表量测数据挖掘效果,该文研究一种基于小波去噪和时频分析的智能电表量测数据挖掘方法。应用小波变换阈值去噪方法对数据集进行去噪,通过惩罚策略选择阈值后,对存在噪声的数据集进行运算,获取去噪后的数据集,根据去噪后的小波系数与存在噪声的小波系数获取最优阈值函数;利用自适应最优径向高斯核时频分析方法,有效将最优阈值函数的数据集分离为自分量信号与互分量信号,精准挖掘智能电表仿真模型数据库内数据,完成智能电表量测数据信息的输出。实验结果表明,所研究方法去噪效果较好,相对误差保持在2%以内,挖掘精度维持在96%以上,应用性能较好。

GNSS整周模糊度研究现状与展望

载波相位测量是全球导航卫星系统(GNSS)实现高精度定位的一个重要观测量。在现阶段,自动驾驶、智慧城市等领域的技术越来越成熟,高精度定位能在这些领域得到广泛的应用,甚至促进这些领域的快速发展,是当前卫星导航领域的热点。快速可靠地确定整周模糊度是载波相位测量中的关键,也是提高GNSS定位精度的关键。本文整理了各种整周模糊度的解算方法,其中重点论述了三频载波模糊度解算(TCAR)方法、递进模糊度整数解算(CIR)方法、最小二乘模糊度去相关平差(LAMBDA)算法等整周模糊度的解算方法及其研究进展,并探讨后续研究的方向。