耐电压测试仪的示值误差的检定和不确定度的分析

主要论述了耐电压测试仪示值误差的表述、检定及其测量不确定度的分析。     

耐电压测试仪的示值误差的检定和不确定度的分析

主要论述了耐电压测试仪示值误差的表述、检定及其测量不确定度的分析。     

电气系统尖峰电压测试仪设计

本文分析了对电气系统有严重影响的尖峰电压，从而提出了电气系统尖峰电压测试仪的设计思路，硬件配置，软件结构，并提出了测试过程中数据采集和数据处理的具体策略，最后提出了进一步提高仪器精度的问题。     

论射频连接器耐射频高电位电压测试

射频连接器"抗电强度"指标很重要。它是射频连接器在工作中防止强电干扰能力的指标。抗电强度好,则连接器才能在整机里安全、可靠的工作。该指标是用耐射频高电位电压测试项目来检测的。而在美军标中对耐射频高电位电压测试项目作了明确的规定。我国上世纪八十年代,以美军标MIL-C-39012B为依据,采用"等同采用"的方针编译、建立了国标GB12272-90和国军标GJB681。经多年来该项目的测试实践以及开发耐射频高电位电压测试仪的实践,发现我国现行标准"详细规范"(同美军标活页规范)规定的"试验电压"太低,必须提高。同时,也必须改进"耐射频高电位电压测试仪"的性能指标。使该仪器能在更高电压下工作,即必须提高"耐射频高电位电压测试仪"的输出电压。我通过技术创新,大幅度的提高了耐射频高电位电压测试仪的输出电压,开发出了SNY-2耐射频高电位电压测试仪。文中介绍了"SNY-2耐射频高电位电压测试仪"的技术指标。这个新型仪器使该项目能在更高的电压下进行试验成为现实。文中还介绍了用该仪器进行测试时,对各种不同规格的射频连接器寻找新的"试验电压"的方法及如何修改提高现行"详细规范"试验电压的途径。该项目在更高的"试验电压"下进行试验,获得通过的受试连接器抗电强度的性能将大幅度的得到提高,有着重要的军事意义。由于耐射频高电位电压测试仪的输出电压大幅度提高,在更高电压下进行试验,故该项目成为我国具有自主知识产权的特有项目。     

新型自动耐压测试仪的设计

本文介绍了一种自动耐压测试仪的新设计方法，它利用ＭＣＳ９６单片机产生ＳＰＷＭ波（正弦脉冲宽度调制）经放大后驱动电力电子功率器件（ＩＧＢＴ０得到幅度可调的正弦交流电，再经升压变压器升压输出，对被测装置进行了耐压试验，测试仪能输出０～１万伏失真度小于８％的无触点电压输出。     

继电保护测试仪用高电压功率放大电路的研制

针对继电保护测试仪的电压功率放大采用集成功率放大芯片价格昂贵,且易损坏,提出了一种性价比高、输出功率大的电压功率放大电路设计方案。首先介绍了继电保护测试仪的硬件结构,并详细分析了电压功率放大电路的原理,计算了功率管的管耗,在此基础上对电路进行了仿真分析,最后对实际电路进行了试验,结果表明,电路可输出功率大、线性度好,可以满足测试仪对电压功率放大的技术要求,并且具有很广的应用前景。     

新型高压绝缘电阻测试仪的研制

本文介绍了一种以集成电路为核心的新型高压绝缘电阻测试仪。它由高压电源、测量电路及附加电路组成，该测试仪输出电压稳定、测试精度高并具有时间显示、定时音响、充电等功能。本文给出了工作原理及技术指标，并讨论了抗干扰措施。     

高精度金属氧化物避雷器测试仪标准装置的研制

为了保证电力系统的安全可靠运行,笔者研制了一种基于DSP和CPLD技术的高精度金属氧化物避雷器测试仪标准装置,产生标准的电压和电流信号,模拟金属氧化物避雷器的运行状态,对金属氧化物避雷器测试仪进行检定。该标准装置采用高分辨率全数字移相技术和反馈控制技术,有效地提高了装置输出精度。送中南国家计量测试中心测试,测试结果表明该装置的输出电压电流的精度达到0.1%,电压与电流之间相位的控制精度达到0.04°,满足对金属氧化物避雷器测试仪检定的要求。     

继电保护测试仪用高电压功率放大电路的研制

针对继电保护测试仪的电压功率放大采用集成功率放大芯片价格昂贵,且易损坏,提出了一种性价比高、输出功率大的电压功率放大电路设计方案.首先介绍了继电保护测试仪的硬件结构,并详细分析了电压功率放大电路的原理,计算了功率管的管耗,在此基础上对电路进行了仿真分析,最后对实际电路进行了试验,结果表明,电路可输出功率大、线性度好,可以满足测试仪对电压功率放大的技术要求,并且具有很广的应用前景.     

一种新型电压互感器二次压降无线测试仪

在组成电能计量装置综合误差的各项误差中,电压互感器二次回路压降所引起的计量误差往往是最大的,因此必须对电压互感器二次回路压降定期进行测量。本文在分析现有各种电压互感器二次回路压降测试技术和仪器的基础上,介绍了一种新型二次回路压降无线测试仪,并给出了实验室和现场测试数据。     

一种研究PTCR老化特性的新方法

阐述了用复阻抗分析的方法来研究ＰＴＣＲ（正温度系数电阻ＰｏｓｉｔｉｖｅＴｅｍｐｅｒａｔｕｒｅＣｏｅｆｉｃｉｅｎｔＲｅｓｉｓ－ｔａｎｃｅ）老化特性的有关方面，重点论述了ＰＴＣＲ的等效电路及其宏微观参数的计算等问题。     

北京城北500 kV变电站GIS系统的交流耐压试验

城北500 kV变电站GIS系统的交流耐压试验,根据GIS设备结构复杂、间隔数量众多、整体电容量较大等特点,合理选择了耐压设备组合方式来满足试验容量的要求,并采用了母线连同GCB单元整体加压的方法。既圆满完成了试验,又最大程度减少了试品的加压次数,从而降低了对试品的绝缘损坏。     

PTCR Effect in BaTiO3: Structural Aspects and Grain Boundary Potentials

Extensive microstructural and structure-property studies on donor doped barium titanate have revealed that the PTCR phenomenon is strongly controlled by the density, number of grain boundaries available to conduction, domain orientation and grain boundary domain coherence. Structural heterogeneities lead to a wide range of grain boundary structures, potential barriers and, therefore, depletion widths. Conduction thus occurs primarily by percolation of electrons through favorably aligned domain pathways and low potential barrier grain boundaries. At the Curie point, the increase in the potential barriers along these pathways is likely to dominate the PTCR effect. To improve theoretical understanding a model needs to take heed of local values of parameters and also incorporate the fact that the bulk of the current flow is only through a certain percentage of grain boundaries. The specific structural factors that have led to an improved qualitative understanding of overall PTCR phenomenon are discussed.     

(Ba,Ca)TiO3 PTCR Ceramics with LaNiO3 Thin-Film Electrodes: Preparation and Characterization of the Interface

Conductive LaNiO₃ thin film electrodes were deposited by chemical solution deposition (CSD) from nitrate solutions onto polycrystalline Al₂O₃ and (Ba,Ca)TiO₃ PTCR ceramic substrates. The electrical properties of the LaNiO₃ thin film on Al₂O₃ and of the interface consisting of LaNiO₃ and the semiconductive oxide ceramic were investigated. The deposited LaNiO₃ films were about 250 nm thick and consisted of nanosized particles. The resistivity of the LaNiO₃ film was about 3 × 10^-3cm at 20°C. The PTCR ceramic consisted of m sized particles and exhibited an electronic resistivity of about 10 cm at 20°C and a steep increase of the resistivity of a few orders of magnitude above the Curie point at about 120°C. The electrical properties of the LaNiO₃/PTCR interface were dominated by the properties of a barrier layer between the PTCR ceramic and the LaNiO₃ electrode. The potential dependence of the impedance indicated that the barrier layer consisted of a depletion layer within the PTCR ceramic, when the flat band potential of LaNiO₃ on the PTCR ceramic at about –250 mV was exceeded. Additionally the formation of an insulating layer at the LaNiO₃ electrode has to be taken into account.     

烧结工艺对BaTiO3基PTCR电阻-温度系数的影响

研究了在制备掺杂Nb2O5的BaTiO3基PTC热敏电阻时,烧结工艺对电阻-温度系数的影响。探讨了通过烧昝工艺提高电阻-温度系数的方法与途径,并通过性能的测试对比以及利用SEM分析,对烧结工艺对电阻-温度系数影响的作用及机理进行了初步讨论。     

Electrical properties of BaPb1+x−y Sb y O3 ceramics derived from a modified sol-gel method

BaPbO₃ ceramics has attracted considerable interest due to the promising electrical applications. For the best control of the microstructure and phase, Sb-doped BaPbO₃ ceramics were prepared by a sol-gel route. Inorganic compounds were used as starting chemicals, citric acid and Ethylene diamine tetra-acetic acid (EDTA) as complex chelate agent, and distilled water as solvent. Experimental results demonstrate that the Sb-doped BaPbO₃ ceramics with homogeneous composition could be prepared by the method mentioned above. Influence of Pb/Ba ratio and Sb concentration on the room-temperature resistivity and the PTCR behavior of BaPb_1+x−y Sb _y O₃ (x = 0.0, 0.1, 0.2 and 0 ≤ y ≤ 0.2) compositions was investigated. The PTCR behavior was related to the Pb/Ba ratio and major compensating defect in BaPbO₃. The lowest electrical resistivity of Sb-doped BaPbO₃ was calculated to be 2.69 × 10⁻⁴ Ω·cm when the Sb concentration y = 12–13 mol%. The 0.5 mol% Sb-doped BaPbO₃ showed the best PTCR behavior, and its Curie temperature is about 850 °C.     

Modification on PTCR behavior of (Sr0.2Ba0.8)TiO3 materials by post-heat treatment after microwave sintering

Abstract

Effect of post-sintering treatment on PTCR behavior of (Sr_0.2Ba_0.8)TiO₃ materials prepared by microwave-sintering (ms) process was compared to that prepared by rapid thermal sintering (RTS) process. The microwave-sintering process needed only 1130°C-40 min to effectively densify (Sr_0.2Ba_0.8)TiO₃ materials. The grain size was around 6 μm and PTCR characteristics was around ρ_max/ρ_min≈ 10^1.75, with T_c = 50°C. Lowering the cooling rate after sintering substantially increases the resistivity jump (ρ_max/ρ_min) from 10² to 10^3.4, without altering the microstructure. The annealing at 1250°C for 2 h markedly increased the resistivity jump to (ρ_max/ρ_min)≈10⁶. On the other hand, the rapid thermal sintering (RTS) process required 1320°C-30 min to fully develop the good microstructure (～15 μm) and PTCR property (ρ_max/ρ_min ～ 10^3.0). Post-sintering process, including cooling rate control and annealing, did not improve the electrical properties of these samples, that is ascribed to the slow-cooling rate characteristics of RTS-process for a temperature lower than 800°C.     

Effect of reoxidation on positive temperature coefficient of resistance behavior for BaTiO3-K0.5Bi0.5TiO3 ceramics

As a positive temperature coefficient of resistivity (PTCR) material, (1-x)BaTiO₃-xK_0.5Bi_0.5TiO₃ (BT-KBT, 0.05≦ x ≦0.15) ceramics without any donor doping were prepared by a conventional oxide mixing method. All samples were sintered in an Ar atmosphere at 1280?~?1350°C, subsequently, reoxidized at 800?~?1100°C in a gas mixture (99 %Ar–1 %O₂). The PTCR behavior of BT-KBT ceramics were investigated in terms of KBT content, reoxidation temperature and time. The results showed that the BT-KBT ceramics exhibited an abrupt increase in their resistivity near the Curie temperature (Tc) after annealing in gas mixture, Tc of 0.9BT-0.1KBT ceramic was shifted to a higher temperature (~150°C). Furthermore, the room-temperature resistivity (ρ_RT) of ceramic samples sintered in Ar and reoxidized in a gas mixture decreased to 10² Ω·cm. The jump in resistivity (maximum resistivity [ρ_max]/minimum resistivity [ρ_min]) was enhanced by three orders of magnitude through a suitable reduction–reoxidation method without sacrificing the ρ_RT.     

Interface mediated transport properties in n-type SrTiO3 : Induced dipole alignment at oxide grain boundaries

Low temperature potentiometry and capacitance measurements based on noncontact atomic force microscopy were used to quantify local properties due to grain boundaries at a 0.05 wt.% Nb-doped SrTiO₃ [001] surface. Local I-V curves were constructed by combining potential steps and transport currents measured at individual grain boundaries (GBs) under different lateral biases. The GBs exhibit a positive temperature coefficient of resistivity (PTCR) effect. A comparison of transport properties and calculations suggest that SrTiO₃ grain boundaries undergo a non-polar to polar state phase transition induced by the large electric field associated with the boundary charge. This is supported by the temperature dependence of the barrier height and the boundary charge obtained by numerical simulation of I-V curves using a double Schottky barrier model. The built-in potential associated with the boundary was directly imaged with frequency-modulated Kelvin probe force microscopy at different temperatures and the results support the previous conclusion.     

Giant Piezoresistive Effects in Single Grain Boundaries of Semiconducting Barium Titanate Ceramics*

Extremely large piezoresistive effects with a gage factor (elastoresistance) of > 1 × 10⁶ in single grain boundaries of thin ceramic bars of semiconducting barium titanate have been observed at room temperature. Thin barium titanate ceramic bars with a diameter in the range of 10 to 20 μm were prepared to consist of single grains joined together in series. Large piezoresistive effects were observed for some of the single grain boundaries in the present samples under compressive stresses, but no distinct piezoresistance was observed in the grain bulk. A giant piezoresistive effect with a gage factor of 3 × 10⁷ was observed for a single grain boundary which exhibited a saw-tooth type PTCR (positive temperature coefficient of resistivity) characteristic with a significantly large bias dependence of it. This demonstrates that the piezoresistive phenomenon may be interpreted in terms of the change of the potential barrier height due to the change of ferroelectric domain morphologies in the vicinity of grain boundaries under mechanical and electric stresses.