垂线观测精度对引张线观测精度的影响分析

基于误差传递原理,分析了垂线作为引张线工作基点时垂线观测精度对引张线最终水平位移观测精度的影响.实例结果表明,垂线观测精度对引张线最终水平位移观测精度有明显影响,且对引张线两边测点的影响程度大于中间测点;采用垂线法和引张线法联合配套观测水平位移时,引张线各测点最终水平位移的理论观测精度不同.     

电容式引张线仪、垂线坐标仪性能特点及改进

电容式仪器已在国内工程中广泛运用,在国外已在10多个国家的工程中得到运用.文中主要介绍了电容式仪器的原理、性能及特点,着重从提高绝缘度与测量稳定性方面介绍了随着技术的进步对电容式仪器技术性能的改进.     

新型光电式垂线坐标仪的研制

介绍了所设计的一种大量程无透镜光电式垂线坐标仪的测量原理、测量电路及测量过程,并通过试验证明了该仪器的可靠性和稳定行.仪器采用线阵点光源提供光照,无需透镜,光源布置简单,易于实现,解决了在潮湿环境中镜头发霉的问题,增加了加热设备,更适合大坝等潮湿环境中应用,可进行现场观测,该垂直坐标仪的量程达到100 mm.     

220kV变电站电容式电压互感器故障分析

电容式电压互感器由于受到运行时间长、运行环境恶劣和操作不规范等因素的影响,较易发生故障,若修复不及时,必然会对变电站安全稳定运行产生不良影响。针对某220kV变电站220kV母线线电压长期越上限问题,利用二次压降测量、就地端子箱加压、误差测试和一次设备拆解分析等方法对电容式电压互感器二次回路及一次设备进行故障分析,最终确定症结在于其220kV电容式电压互感器一次设备内部发生故障,进而提出了故障处理方案。由此可知,提高电容式电压互感器故障检测效率和检测水平有利于发现和排除电压互感器故障,且由于调控中心对母线线电压监测的局限性可能导致某种情况下不能及时发现故障,因此优化变电站重要参数的监控策略是消除此类故障隐患的有效措施。     

状态监测在电容式电压互感器全寿命周期管理中的应用

电容式电压互感器电磁单元发生故障的概率明显高于电磁式电压互感器,为了进一步提高电容式电压互感器运行的可靠性,结合电容式电压互感器的结构特点,提出了采用油位观察、红外测温、二次电压监测、电磁单元油样分析、电气试验等检测手段,对电容式电压互感器运行状态进行监测,实现设备的全寿命周期管理。采用该方法,可及时发现并处理站内设备异常,提高了设备运行的可靠性。     

小浪底电厂220kVCVT介质损耗角正切值异常原因及预防措施

以小浪底电厂220 kV开关站电容式电压互感器为例,针对2006、2007年开关站春季检修中遇到的电容式电压互感器介质损耗角正切值增大问题,以电气预防性试验数据为依据判断问题的原因及故障点,通过对设备分解检查,判断出电容式电压互感器电磁单元部分故障是设备介质损耗角正切值异常的根源,并提出了预防措施.     

电容式煤粉浓度传感器的实验研究

针对输送管道中煤粉浓度测量存在的问题,通过试验找出了双极板结构电容式传感器测量准确性差的原因,并试制出了一种8极板结构的电容式传感器,测量时每次采样单向向前转动1个电极位置,每采样4次取其算术平均值作为传感器本次测量输出值.实验表明,这种方法能够有效地消除流型及相分布对浓度测量的影响,使测量准确度和线性度显著提高.     

李家峡拱坝水平位移变化规律异常成因分析

针对李家峡大坝垂线监测资料分析中发现的异常现象,对其进行物理成因分析,建立位移统计模型分析了其主要影响因素,并通过对李家峡大坝的大量模拟研究建立了三维有限元模型,在多模型,多工况、多种材料参数组合计算的基础上,分析了大坝变形异常成因,查清了水平位移变化规律异常的原因.     

监测汽轮发电机组振动的一种好工具——JDZ-1智能振动监测分析仪简介

为了适应安全生产和满足火电机组调试工作的需要,吉林省电力试验研究所最近研制出JDZ-1智能振动监测分析仪。 1.该仪器具有以下功能:可以同时在屏幕上显示转速值和7个通道的振幅值,并且达     

水口水电站坝顶水平位移监控指标的拟定

在对水口水电站大坝结构力学特征和对位移监测资料(垂线)进行衔接的研究分析基础上,利用小概率法和结构分析的混合模型法拟定了水口水电站大坝水平位移的一级安全监控指标。通过对两种方法的比较,可以确定结构分析的混合模型法的计算结果更为合理。     

Capacitance requirements of self-excited induction generators

A simple method for computing the minimum value of capacitance, C min. required for initiating voltage build-up in a three-phase self-excited induction generator (SEIG) is presented. Based on the steady-state equivalent circuit model, a consideration of the circuit conductances yields a sixth-degree polynomial in the per-unit frequency. The polynomial can be solved for real roots, which enables the value of C_min to be calculated. Critical values of load impedance and speed, below which the machine fails to self-excite irrespective of the capacitance used, are found to exist. Closed form solutions for C_min are derived for no-load and inductive loads. Using the same numerical approach, an interative procedure is developed for predicting the capacitance required for maintaining the terminal voltage at a preset value when the generator is supplying load. Experimental results obtained on a 2 kW induction machine confirm the feasibility and accuracy of the proposed methods     

Capacitance decay of nanoporous nickel hydroxide

Nanoporous nickel hydroxide Ni(OH)₂ coated on nickel foam by using a chemical bath deposition method shows a high specific capacitance of 2200 F g⁻¹ at a discharging current density of 1 Ag⁻¹. After 500 charge-discharge cycles, the specific capacitance is stabilized at 1470 Fg⁻¹, and there is only a 5% fall in specific capacitance during the following 1500 cycles. The relationship between the capacitance decay and changes in the microstructure and morphology of nanoporous Ni(OH)₂ is investigated. The results show that phase transformation and the growth of particle/crystal size, rather than the formerly proposed flaking off of Ni(OH)₂, are the major factors contributing to the capacitance decay.     

Capacitance Requirements for Isolated Self Excited Induction Generators

Capacitance requirements for isolated self excitd induction generators are discussed. It is shown that numerical methods based upon the steady state as well as operational equivalent circuit give similar predicted values. An analytical method is proposed to compute, Cmin, the minimun capacitance value required for self excitation under no load conditons. It is shown that Cmin is inversely proportional to the square of the speed. Furthermore, it is inversely proportional to the maximum saturated magnetizing reactance. The theoretical results are verified experimentally for a number of test machines and a good agreement is observed between the theoretical and the experimental values. The influence of load impedance and its power factor on the terminal capacitance required to maintain self excitation under steady state is also examined and it is shown that when machine is loaded, the terminal capacitance should be several times that required at no load. Furthermore, the influence of terminal capacitor upon the maximum available output power fron isolated induction generators is also examined.     

浅谈泵站电气的电容补偿

为了降低泵站电力系统在电力输送中的电能损耗,提高电力输送电力的容量和质量,就需要通过在系统中适当的增加电容的方式对消耗掉的无功功率进行补偿.主要从电力电容补偿的补偿优势、补偿原理、补偿方法、及电容补偿安全运行这几个方面进行阐述.     

应用电容层析成像法测量煤粉浓度的研究

采用电容层析成像技术(ECT),对常温下稀疏气力输送的煤粉浓度进行测量.为更好地利用电容传感器敏感场的分布特性,实验系统中安装了1个旋风分离装置,通过旋风分离作用将固体颗粒主要集中在壁面区域,传感器电极布置在分离器直管上.通过对管道截面上固体体积分数、波动特性以及体积分数平均测量结果的比较分析,证明这种方法可获得准确可靠的测量结果.     

Capacitance studies of cobalt compound nanowires prepared via electrodeposition

The capacitor properties of cobalt compound nanowire (CCNW) electrodes, prepared by the one-step electroreduction of [Co(NH₃)₆]³⁺ in water, have been investigated. The CCNW electrode changes its various properties during its growth. During the initial growth stage, the CCNW electrodes consist of nanowires with smooth surfaces and have a specific capacitance (C_m) of 310 F g⁻¹. During the middle stage, prickles grow on the CCNW surface, leading to a reduction in its real surface area and its C_m value to 230 F g⁻¹. During the final stage, further growth of the prickles is accompanied by the fusion of the CCNWs, and hence, a drastic decrease in the real surface area. However, a maximum capacitance of C_m = 420 F g⁻¹ was obtained during this stage. This unexpected capacitance change was discussed in terms of the effects of rapid ion transfer and the electroactive material/electrolyte interface area. In addition, the aging effect and the cycle life of the CCNW electrode were also investigated.     

Capacitance properties of poly(3,4-ethylenedioxythiophene)/polypyrrole composites

Poly(3,4-ethylenedioxythiophene)/polypyrrole composite electrodes were prepared by electropolymerization of 3,4-ethylenedioxythiophene (EDOT) on the surface of polypyrrole (PPy) modified tantalum electrodes. The electrochemical capacitance properties were investigated with cyclic voltammetry (CV), galvanostatic charge–discharge and electrochemical impedance spectroscopy (EIS) techniques with two- or three-electrode cell configuration. The data showed that the specific capacitance of composite electrodes, due to the synergic effect of poly(3,4-ethylenedioxythiophene) (PEDOT) and PPy, is much higher than the values of either pure PEDOT or pure PPy electrodes. Moreover, the composites prepared on the surface of PPy with horn-like structure allow the specific capacitance up to more than 200 F g⁻¹ and have a good cycleability. This implies that PEDOT/PPy composites are promising to be used as electrode material of supercapacitors.     

Capacitance of porous carbon electrode in mixed salt non-aqueous electrolytes

Capacitances of a porous carbon electrode in non-aqueous electrolytes containing tetraethylamonium tetrafluoroborate (TEABF₄) and a lithium salt with various compositions have been investigated for the potential use in electric double layer capacitor. In the electrolyte prepared by dissolving TEABF₄ and LiBF₄ into the mixed solvent of ethylene carbonate (EC) with diethyl carbonate (DMC), an activated carbon fiber (ACF) electrode exhibits a larger capacitance than in TEABF₄ single salt electrolyte on cyclic voltammograms. The symmetrical capacitor cell containing the LiBF₄-TEABF₄ mixed salt electrolyte also exhibits larger capacitance on a constant-current test compared with that containing the TEABF₄ single salt electrolyte, while the capacitance degradation is observable for this cell at a significant extent, while the test under controlled potential of the ACF electrode to −0.2 to 1.0 V vs. Ag provides somewhat stable capacitance over 30 cycles.     

电容法测量蒸汽湿度的可行性研究

结合介电理论以及水和水蒸气的性质,研究了水和水蒸气的静态相对介电常数随压力和温度的变化趋势,并分析了造成水和水蒸气介电常数变化的原因.研究结果表明,水的介电常数受温度的影响更大,而水蒸气的介电常数则受压力的影响更大.由于水和水蒸气的介电常数差异非常大,根据电容法测量原理,利用圆筒形电容传感器进行了湿度测量试验,结果表明利用电容法测量饱和湿蒸气湿度是可行的.