基于GPRS的农网终端变电站(塔)自动化系统

针对目前我国农村电网的实际情况,设计开发了基于GPRS通信的变电站(塔)自动化系统.通过对目前监控系统中常用的通信方式进行比较,选择GPRS组建专用APN网络,既能降低成本,又能达到要求的可靠性.采用网络仪表替代传统的RTU,解决了配电自动化改造工程中存在的困难.     

反铁磁性交换作用对(Ga,TM)As居里温度的影响

基于Zener模型,详细分析了反铁磁性交换作用对(Ga,TM)As(TM=Sc,Ti,V,Cr,Mn,Fe,Co,Ni)居里温度的影响,结果表明,反铁磁性交换作用对n型半导体居里温度的影响程度远远大于对p型半导体居里温度的影响,而且在考虑了反铁磁性交换作用后,除了(Ga,Cr)As和(Ga,Mn)As以外都不可能实现室温铁磁性,(Ga,Cr)As和(Ga,Mn)As的掺杂浓度为13.1%和18%时可获得室温铁磁性,但是反铁磁性交换作用相对强弱增强到y=0.01时,任何掺杂浓度都不能实现室温铁磁性。     

Operating characteristics of a superconducting fault current limiting transformer (SFCLT) and enhancement of electric power system stability

We have been investigating the feasibility of a superconducting fault current limiting transformer (SFCLT) with the functions of fault current suppression and system stability improvement. This paper discusses these functions with consideration of overvoltage and thermal characteristics of SFCLT, and their dependence on recovery time into superconducting state after the quench of SFCLT. Simulation results using EMTP suggested that SFCLT would be coordinated with the background power system under the appropriate superconducting recovery time. The operating parameters of SFCLT were also optimized in a simplified power transmission model system. © 2002 Wiley Periodicals, Inc. Electr Eng Jpn, 142(2): 40–47, 2003; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10070     

Performance of a 3000/6000 V, 1000 kVA class superconducting transformer developed for a prospective power transmission model system integrated under superconducting environment (PROMISE)

A 3000/6000V, 1000 kVA class superconducting transformer (SC-Tr) was developed for a Prospective Power Transmission Model System Integrated under Superconducting Environment (PROMISE). In this transformer, the core and superconducting windings are immersed in liquid helium and the major insulation is provided by the liquid helium. This paper describes both the design features and measured characteristics of the SC-Tr. Fundamental characteristics of the SC-Tr are obtained through no-load, short-circuit tests and quench experiments. The results of the no-load test have verified that the SC-Tr has the capability to withstand ac voltage of 3000/6000 V of 60 Hz without any partial discharge. The short-circuit tests have proved that the SC-Tr is capable of carrying ac current of 170 Arms without quench in the superconducting windings. Furthermore, in a real-load experiment with the PROMISE, electric power of 3800 V-460 kVA of 50 Hz in high-voltage side is transmitted through this SC-Tr.     

变压器低压侧小区差动保护的思考

根据变压器低压侧小区差动保护原理和动作方程,推导出低压侧不同故障类型时该保护的动作行为。由推导发现,当低压侧绕组内部特定处相间短路时,非故障相差动会动作。同时详细分析了不同故障类型时,流经变压器各侧短路电流的幅值和相位。综合分析得出:由于变压器低压侧绕组采用三角形接法,其绕组内相间短路时各相相互影响,三角形绕组内短路电流会形成环流,从而导致了非故障相差动动作。该结论对于工程事故分析具有一定的指导意义。     

风电接入对继电保护的影响(三)——风电场送出变压器保护性能分析

仿真分析发现双馈式风电机组低电压穿越期间的短路电流频率随故障前工况偏移工频。当变压器内部故障时,基于相量值的差动与制动电流将大范围波动,基于采样值的差动保护在某些采样点动作条件不满足,差动保护均无法准确稳定地动作。以某地区实际风电接入为例,在EMTDC平台上对风电场主变压器以及风电集群再升压变压器保护进行离线动作性能测试分析,结果表明,基于相量值及基于采样值的差动保护均无法保证快速动作,风电机组类型、运行工况、故障位置、故障类型及短路容量比是影响风电场送出变压器保护正确动作的因素。     

Protonic Conduction in Perovskite-type Oxide Ceramics Based on LnScO3 (Ln=La, Nd, Sm or Gd) at High Temperature

Ionic transport properties of perovskite-type oxides based on LnScO₃, Ln_{1- x}Ca_xScO_3- (Ln=La, Nd, Sm and Gd) and LaSc_1-xMg_xO_3- were studied using an electrochemical method at elevated temperatures. Conductivity in these oxide systems increased by more than three orders of magnitude upon doping with divalent atoms such as Ca or Mg. However, when x0.1, conductivities are almost independent of x in La_{1- x}Ca_{xScO_3-} and LaSc_{1- x}Mg_xO_3-. Gd_0.9Ca_0.1ScO_3- showed lower conductivity than Ln_1-xCa_xScO_3- (Ln=La, Nd and Sm). Protonic conduction in these oxides under hydrogen containing atmospheres was confirmed by emf measurements of hydrogen concentration cells and by electrochemical hydrogen pumping using these oxides as a diaphragm. In LaSc_1-xMg_xO_3- the transport number of protons under hydrogen containing atmosphere was unity, suggesting that electronic conduction never became dominant, even under strong reducing conditions. Under condition of high oxygen partial pressure, the transport number of ions was less than 0.1, suggesting that the majority conductive carriers under such conditions were holes.     

室内外工况对空调制热性能的影响研究(下篇)

国家标准“房间空气调节器”（GB／T7725．2004）规定空调器的额定高温制热的试验工况是：室外干湿球温度7／6℃,室内干球温度20℃。空调器的铭牌上标示的正是额定高温制热量,客户选择空调时是以铭牌上的制热量为根据的。但在实际的使用中,空调制热更多是在0℃以下的室外空气中进行的,此时空调的制热量会与额定高温制热量有较大差别,这导致很多消费者抱怨空调的制热性能不好。     

室内外工况对空调制热性能的影响研究(上篇)

空调在实际的制热运行时,室内外工况与国标有很大差异。本文以额定高温制热量为7700W的柜式空调为对象,研究了室外机不除霜时室内、外干球、湿球温度对空调制热量和送风温度的影响规律。结果表明室外干球、湿球和室内干球温度对制热量和送风温度影响较大,室内湿球温度对制热性能没有影响。     

基于VB的温度实时监测系统设计

利用面向对象特性的VB、VC软件开发的温度监测系统，不仅可显示当前多个温箱的温度，进行数据存储及打印，还可实时观测当前各温箱的温度曲线，为工作人员操作提供方便。     

低色温(3450～2700K)白光LED的发射光谱和色品质特性

本文报告蓝色InGaN基芯片和光转换黄绿色和红色荧光体结合的属于3450K、2900K及2700K低色温、高显色性白光LED的发射光谱、色品坐标、显色指数Ra、光效η等性质以及这些光学特性与正向电流IF的关系.揭示这些关系的变化及相关色温差ΔTc的变化规律,并对这些结果进行讨论.在IF=20mA下,3450K、2900K及2700K低色温白光LED的光效η(lm/w)分别为56.4、51.1及43.3,它们的Ra均为85左右.     

电器设备组件特别是接线端子容许温升的导则--IEC60943技术报告(三)

IEC60943技术报告是由IEC32熔断器技术委员会编制，并于1998年发布的。技术报告旨在指导评估稳定状态下载流电器设备组件的温升容许值。技术报告提供了触头接触电阻的计算和基本老化机理；触头和接线端子的温度和温升计算；不同组件，特别是触头，接线端子和连接它们的导体的最大容许温度和温升；IEC各产品委员会确定最大容许温度和温升必须遵守的主要程序。     

YD双速54槽8/4极电机降温方法浅析

双速电机是利用特殊接线法来改变定子绕组的极对数,以达到变极调速的目的。介绍如何通过改变54槽8/4极电机绕组布线,达到降低温升、提高电机运行性能的目的。     

The effects of self-movement, observation, and imagination on mu rhythms and readiness potentials (RP's): toward a brain-computer interface (BCI).

Current movement-based brain-computer interfaces (BCI's) utilize spontaneous electroencephalogram (EEG) rhythms associated with movement, such as the mu rhythm, or responses time-locked to movements that are averaged across multiple trials, such as the readiness potential (RP), as control signals. In one study, we report that the mu rhythm is not only modulated by the expression of self-generated movement but also by the observation and imagination of movement. In another study, we show that simultaneous self-generated multiple limb movements exhibit properties distinct from those of single limb movements. Identification and classification of these signals with pattern recognition techniques provides the basis for the development of a practical BCI.     

电器设备组件特别是接线端子容许温升的导则-IEC60943技术报告(二)

IEC60943技术报告是由IEC32熔断器技术委员会编制,并于1998年发布的.技术报告旨在指导评估稳定状态下载流电器设备组件的温升容许值.技术报告提供了触头接触电阻的计算和基本老化机理;触头和接线端子的温度和温升计算;不同组件,特别是触头,接线端子和连接它们的导体的最大容许温度和温升;IEC各产品委员会确定最大容许温度和温升必须遵守的主要程序.     

2,4,6-三(2-烯丙基苯氧基)-1,3,5-三嗪与双马来酰亚胺共聚物的研究

以三聚氯氰为原料，合成三嗪烯丙基衍生物，并与双马来酰亚胺发生共聚反应。研究了2，4，6-三(2-烯丙基苯氧基)1，3，5-三嗪(TAPT)与二苯基甲烷双马来酰亚胺(BMDPM)不同组成比例对共聚物的力学性能的影响。用TGA分析研究了共聚物的热稳定性。结果表明TAPT／BMDPM组成比在45％～60％时，共聚物的力学性能有明显改善，但热稳定性能却比BMDPM均聚物稍有降低。     

AgW(65)触头材料断口高温高湿交变试验性能研究

采用不同介质进行球磨工序并研究在高温高湿环境下材料断面成分及物相的变化,探究球磨分散介质对材料抗氧化性能的影响.通过高温高湿交变试验前后AgW(65)电接触材料断面形貌以及成分物相对比,发现相对去离子水,采用乙醇作为球磨分散介质时,AgW(65)电接触材料中的W颗粒在高温高湿环境下表现出良好的耐腐蚀性能.     

具有低温度系数的Sm 0.8Re0.2(CobalFe0.22Cu0.06Zr0.03)7.4(Re=Gd,Er)两种烧结磁体的磁性能比较

比较了成分分别为Sm0.8Gd0.2(CobalFe0.22Cu0.06Zr0.03)7.4和 Sm0.8Er0.2(CobalFe0.22Cu0.06Zr0.03)7.4的两种烧结磁体的磁性能、温度特性以及热处理工艺对二者的影响.分析表明,在相同的工艺条件下,当经过1160～1200℃范围内的固溶热处理、再经过时效处理,Sm0.8Er0.2(CobalFe0.22Cu0.06Zr0.03)7.4磁体的室温磁性能比Sm0.8Gd0.2(CobalFe0.22Cu0.06Zr0.03)7.4要好,但其温度稳定性却相反.同时发现Sm0.8Er0.2(CobalFe0.22Cu0.06Zr0.03)7.4的矫顽力对热处理工艺中的固溶温度比较敏感,两种磁体的退磁曲线方形度与固溶处理温度有着很大的关系.在一定温度范围内,固溶温度愈高磁体的退磁曲线方形度愈好.