电子式互感器误差分析

为提高电子式互感器的测量准确度,研究了其系统中的误差特性。在对其中噪声特点进行分析的基础上,对前级放大器、A/D转换器以及低压侧信号处理系统等单元的误差特性进行了研究,指出了影响系统测量准确度的关键环节。在此基础上,给出了元件选择和系统设计的参照原则,并研制出220 kV电压等级电子式电流互感器样机。试验结果表明:该互感器满足IEC 0.2级测量准确度要求,并且-30℃~ 70℃范围内,测量比差小于±0.1%,角差小于±2′。验证了误差分析的有效性。     

电子式电流互感器的误差分析与在线试验研究

为获得电子式互感器在长期运行过程中的误差与部分影响参量的关系和规律,建立了电子式互感器运行特性在线实验平台。在分析电子式电流互感器误差来源的基础上,在东山变电站对挂网运行的电子式互感器进行试验。通过对试验数据进行研究,得到了电子式电流互感器误差受温度、负荷变化的影响规律及长期运行过程中的稳定性,为准确评估电子式电流互感器的稳定性和可靠性提供了重要支撑。     

电阻分压的10KV电子式电压互感器分析

基于电阻分压器的电子式电压互感器的原理、结构和输出信号等与传统的电压互感器有很大不同,其性能主要受电阻特性和杂散电容的影响。本文从等效电路的角度分析了电阻特性和杂散电容对电子式电压互感器测量准确度的影响;利用Ansoft软件包建立分压器的有限元模型对杂散电容进行了计算分析,并根据杂散电容分布对屏蔽罩进行了设计。在理论分析基础上,研制了一台电阻分压式的10KV电子式电压互感器,并进行了准确度测试。     

电流型电子式电压互感器的温度稳定性研究

针对一种电流型电子式电压互感器(EVT)的温度稳定性进行了分析,指出高压电容器和一次侧信号处理单元中的积分电路是影响其温度稳定性的主要环节. 设计了利用正、负温度系数数值相等的多个电容单元串联组成高压电容器的温度补偿方案,有效地改善了高压传感部分的温度稳定性;提出利用热敏电阻对积分电容的温度特性进行补偿的方法,减小了温度变化给积分电路带来的误差. 依照IEC60044-7的要求,对研制的110 kV电流型EVT样机进行了温度影响准确度试验,试验结果表明设计的温度补偿方案有效,互感器在-40 ℃～+70 ℃温度范围内,满足0.2级测量准确度要求.      

电子式电压互感器的研究与设计

在分析电子式电压互感器当前技术和发展的基础上,系统总结并提出了电子式电压互感器的原理和设计要求.分析了传光型电压互感器的系统组成,给出了以电容分压器测量电压的电子式电压互感器的原理和设计方法,论述了电子式电压互感器的优点和性能.     

电压互感器宽频误差自动测量装置及试验研究

为准确测量电压互感器的宽频误差,基于测差原理,运用锁相放大器和Lab VIEW技术,研制了一套电压互感器宽频误差测量装置,实现了互感器误差测量的自动化与智能化。介绍了宽频误差测量基本原理及装置整体设计方案,并通过工频误差校准、自校结果比对、频率特性及稳定性等试验,对该装置的性能进行了测试与验证。测试结果表明,装置在50 Hz～10k Hz范围内,其比差测量精度优于5×10~(-7),角差测量精度优于0. 2μrad,且频率响应特性十分平坦。     

110 kV智能变电站复杂环境下电子式互感器校验方法

为解决智能变电站电子式电压、电流互感器现场误差校验问题,分别提出了以IEC61850为通讯规约的基于比较法的电子式电压、电流互感器现场校验方法.以某110kV智能变电站为背景,首先分析了该智能变电站电子式电压、电流互感器的配置情况,然后详细阐述了使用所提出方法进行校验时一次设备的操作过程.在研究所提出的电子式互感器现场误差校验方法工作机理的基础上,建立了电子式电压互感器现场校验方法的一次等效电路,同时还建立了其等效数学模型.现场应用结果不仅证明了本文研究内容的有效性与正确性,而且表明该智能变电站的电子式电流互感器,可做0.2S级电流计量互感器使用;电子式电压互感器,可做0.2级电压计量互感器使用.     

电压互感器误差特性的探讨

本文对电容式电压互感器的负载误差特性和误差补偿进行了探讨,提出了限制电压互感器绕组导线的电流密度,减小绕组的漏磁以降低漏抗,从而改善负载误差特性,是提高电压互感器准确度的有效措施。     

一种用于电子式电流互感器的信号处理方法

提出了一种用于电子式电流互感器的信号处理方法。该方法在光强调制原理的基础上,通过将光强调制时的直流偏置信号作为参考信号,利用发光管及光电管的线性区,将高压侧模拟信号调制后的光信号直接传输至低压侧;可以根据参考信号的衰减计算交流信号的衰减,由此解决了使用模拟光信号进行测量时存在的精度较低的不足。可用于电子式电流互感器的设计以实现母线电流的测量。介绍原理及实现过程,并对系统设计的关键问题进行了分析。实验表明,该方法可用于测量及保护用电子式电流互感器的设计。     

浅析电流互感器的准确度等级对电网设备安全的影响

电流互感器是电网中常用的电力设备,按其作用可分为测量用电流互感器和保护用电流互感器,本文对这两类电流互感器不同准确等级的特性进行分析,阐述了不同准确度等级的适用范围及不同准确度等级混用对电网设备安全的危害。     

Markedness and its Interpretation in Language Use

Language markedness is a common phenomenon in languages, and is reflected from hearing, vision and sense, i.e. the variation in the three aspects such as phonology, morphology and semantics. This paper focuses on the interpretation of markedness in language use following the three perspectives, i.e. pragmatic interpretation, psychological interpretation and cognitive interpretation, with an aim to define the function of markedness.     

Features of Women's language

Language is a means of verbal communication. People use language to communicate with each other. In the society, no two speakers are exactly alike in the way of speaking. Some differences are due to age, gender, statue and personality. Above all, gender is one of the obvious reasons. The writer of this paper tries to describe the features of women＇s language from these perspectives： pronunciation, intonation, diction, subjects, grammar and discourse. From the discussion of the features of women＇s language, more attention should be paid to language use in social context. What＇s more, the linguistic phenomena in a speaking community can be understood more thoroughly.     

An Analysis of Catherine＇s Character——Wuthering Heights

Wuthering Heights, Emily Bronte＇s only novel, was published in December of 1847 under the pseudonym Ellis Bell. The book did not gain immediate success, but it is now thought one of the finest novels in the English language. Catherine is the key character of this masterpiece, because everybody and everything center on her though she had a short life. We can understand this masterpiece better if we know Catherine well.     

Lower Paleozoic oil relationships within Williston Basin, Canada

The Williston Basin is a significant petroleum province, containing oil production zones that include the Middle Cambrian to Lower Ordovician, Upper Ordovician, Middle Devonian, Upper Devonian and Mississippian and within the Jurassic and Cretaceous. The oils of the Williston Basin exhibit a wide range of geochemical characteristics defined as "oil families", although the geochemical signature of the Cambrian Deadwood Formation and Lower Ordovician Winnipeg reservoired oils does not match any "oil family". Despite their close stratigraphic proximity, it is evident that the oils of the Lower Palaeozoic within the Williston Basin are distinct. This suggests the presence of a new "oil family" within the Williston Basin. Diagnostic geochemical signatures occur in the gasoline range chromatograms, within saturate fraction gas chromatograms and biomarker fingerprints. However, some of the established criteria and cross-plots that are currently used to segregate oils into distinct genetic families within the basin do not always meet with success, particularly when applied to the Lower Palaeozoic oils of the Deadwood and Winnipeg Formation.     

低渗透非均质砂岩油藏启动压力梯度研究

理论推导与室内实验相结合,建立了低渗透非均质砂岩油藏启动压力梯度确定方法。首先借助油藏流场与电场相似的原理,推导了非均质砂岩油藏启动压力梯度计算公式。其次基于稳定流实验方法,建立了非均质砂岩油藏启动压力梯度测试方法。结果表明:低渗透非均质砂岩油藏的启动压力梯度确定遵循两个等效原则。平面非均质油藏的启动压力梯度等于各级渗透率段的启动压力梯度关于长度的加权平均;纵向非均质油藏的启动压力梯度等于各渗透率层的启动压力梯度关于渗透率与渗流面积乘积的加权平均。研究成果可用于有效指导低渗透非均质砂岩油藏的合理井距确定,促进该类油藏的高效开发。     

On Tragic Consciousness In The Works By Ernest Hemingway

As an American modern novelist who were famous in the literary world, Hemingway was not a person who always followed the trend but a sharp observer. At the same time, he was a tragedy maestro, he paid great attention on existence, fate and end-result. The dramatis personae's tragedy of his works was an extreme limit by all means tragedy on the meaning of fearless challenge that failed. The beauty of tragedy was not produced on the destruction of life, but now this kind of value was in the impact activity. They performed for the reader about the tragedy on challenging for the limit and the death.     

Design and analysis of generic LBS application developing platform

Location based services is promising due to its novel working style and contents.A software platform is proposed to provide application programs of typical location based services and support new applications developing efficiently. The analysis shows that this scheme is easy implemented, low cost and adapt to all kinds of mobile nework system.     

Achieving Unusual States of Matter Under High Pressure

正The periodicity of the elements and the non-reactivity of the inner-shell electrons are two related principles of chemistry,rooted in the atomic shell structure.Within compounds,Group I elements,for example,invariably assume the+1 oxidation state,and their chemical properties differ completely from those of the p-block elements.These general rules govern our understanding of chemical structures and reactions.Using first principles calcula-     

Exchange-Correlation and Electronic Excitation Energies from Pairing Matrix Fluctuations

We have developed an adiabatic connection to formulate the ground-state exchange-correlation energy in terms of pairing matrix linear fluctuations.This formulation of the exchange-correlation energy opens a new channel for density functional approximations based on the many-body perturbation theory.We illustrate the potential of such approaches with an approximation based on the particle-particle Random Phase Approximation(pp-RPA).This re-     

Density Functional Theory for the Response of Periodic Systems to Electric Fields Based on the Vector Potential Approach

正The electronic and nuclear(structural/vibrational)response of 1D-3D nanoscale systems to electric fields gives rise to a host of optical,mechanical,spectral,etc.properties that are of high theoretical and applied interest.Due to the computational difficulty of treating such large systems it is convenient to model them as infinite and periodic(at least,in first approximation).The fundamental theoretical/computational problem in doing so is that