一起660 MW汽轮发电机转子匝间短路缺陷的查找与分析

在汽轮发电机转子故障中,最常见的就是匝间短路缺陷,为了能够给相关故障的处理和分析提供参考,文章对诊断一台660MW发电机转子绕组匝间短路的方法进行探讨,并对排查故障的过程及方法进行确认.     

基于旋转弱耦合与强耦合计算方法的大型汽轮发电机转子流体场与温度场研究

针对大型空冷汽轮发电机转子旋转状态下,转子内部流体流量和转子线圈温度难以准确测量的问题,对转子内部流体流动规律和温度分布进行了流体场和温度场研究.以一台100MW空冷汽轮发电机为例,建立了三维流体与传热耦合计算模型.基于旋转弱耦合与旋转强耦合两种有限元计算方法,对该发电机的转子进行流体场和温度场计算.弱耦合计算方法主要根据流体流动的伯努利方程与计算流体力学相关方程联合求解,强耦合计算方法主要通过计算旋转流体力学方程求解.研究了转子额定励磁电流,转速3 000r/min时,转子内部通风道流体温度与转子绕组温度的相互关系.并将两种计算方法对同一转子的流体流量和线圈温升结果做了对比分析,最后将两种计算方法所得的转子线圈温度计算结果与试验实测结果对比.结果表明:弱耦合计算方法与实测值误差为4.6%,强耦合计算方法与实测值误差为2.6%,两种计算方法均能满足工程计算的误差要求,旋转强耦合计算方法计算精度高于旋转弱耦合计算方法.     

1000 MW级轴向氢冷汽轮发电机定子铁心通风系统

对采用轴向通风冷却系统的1000MW级汽轮发电机定子铁心的通风和发热进行了研究。对定子铁心，根据节点单元等效热阻网络法的要求，建立了定子铁心中典型的矩形单元、扇形单元、通风孔单元和齿顶单元模型，给出了这些单元等效热阻的计算方法，建立了各单元热平衡方程组。以一台930MW的水氢氢汽轮发电机为例，计算出了其定子铁心通风孔单元的通风和气体温升，以及每个铁心单元的温升，试验验证了这种方法的正确性。     

汽轮发电机转子绕组稳定接地故障的检查

大型汽轮发电机转子绕组由于某种原因发生接地故障，本文介绍了转子绕组接地的概况，查找转子接地的试验方法及试验结果分析。     

大型水轮发电机电磁场模型及其对温度场的影响

为了准确分析大型水轮发电机的损耗和发热问题,分别建立了2维稳态电磁场、运动电磁场和场路耦合的有限元模型,并以1台36MW贯流式水轮发电机为例,对转子铁芯损耗和阻尼绕组损耗进行了计算。在此基础上,结合3维温度场有限元计算,分析了3种不同电磁场模型对转子热源和温度计算结果的影响,并与试验数据进行了对比。结果表明,场路耦合模型计算精度更高,额定工况时每根阻尼条的损耗不等,背风面阻尼条的发热明显大于迎风面的阻尼条,转子最高温度位于阻尼绕组而非励磁绕组。研究结果对提高大型水轮发电机转子损耗和温度场的计算精度以及设计、运行的可靠性具有参考价值。     

发电机转子绕组匝间短路故障的分析与检测

深入分析了发电机发生转子绕组匝间短路故障后的电磁特性,得出当发电机发生匝间短路故障后,若端电压和有功功率保持不变时,无功功率会相对减小的结论;同时推出在一定的状态下,有功功率、无功功率和励磁电流之间的对应关系。利用人工神经网络具有不需要精确的数学模型及诸多参数的优点,把人工神经元网络方法引入到发电机转子绕组匝间短路的故障诊断技术中,可通过对故障样本的比较,诊断出转子绕组匝间短路的故障情况。     

汽轮发电机转子绕组稳定接地问题研究

大型汽轮发电机转子绕组由于某种原因发生接地故障,本文介绍了转子绕组接地的概况,查找转子接地的试验方法及试验结果分析。     

汽轮发电机定子绕组内部故障的参数计算和仿真

为了对汽轮发电机定子绕组内部故障进行快速保护以减轻造成的损害 ,必须对各种内部故障瞬态有全面的分析。论文用气隙磁导的概念和谐波分析的方法计算了汽轮发电机内部故障时的实际回路参数 ,并简化考虑了实心转子的涡流效应。用多回路方法仿真研究了定子绕组的各种内部故障瞬态。通过对一台模拟发电机的内部短路试验与仿真结果的对比 ,证明了该文提出的多回路模型和方法的正确 ,为研究汽轮发电机内部故障瞬态及其保护方案提供了理论基础。     

发电机定、转子绕组故障浅析及处理

发电机经过十余年的运行,定、转子绕组分别出现电晕和匝间短路等故障,对电厂的安全运行造成严重影响。通过分析定子绕组电晕和转子绕组匝间短路等故障的原因,提出了处理方法,为运行检修人员提供参考。     

同步发电机偏心与绕组短路故障对磁场及电磁振动的影响

以1台6 MW汽轮同步发电机为例,对转子静偏心、定子匝间短路及其联合故障下的磁场、电磁力和电磁振动进行研究。在气隙磁场不对称情况下,以等效电路为基础的经典算法将不再适用,为此建立发电机的有限元模型,基于瞬态磁场的计算结果,给出不同故障类型下的气隙磁场变化特征,并得到发电机不同运行状态下的径向电磁力及其与对应故障参数的变化关系。将电磁力作为载荷,对发电机的电磁振动进行研究,通过比较正常运行和故障运行状态下的位移曲线,定性分析不同故障对电磁振动的影响。研究结果表明:且该振动特征可以为发电机偏心和绕组短路故障诊断提供理论依据。     

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.     

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     

Call for Papers

<正>"The Journal of Shanghai Normal University:Mathematics"is published by Shanghai Normal University as regular issues of The Journal of Shanghai Normal University each year from 2014 in English.The editors-in-chief of the issues are professors Yuhao Cong and Maoan Han.The Journal of Shanghai Normal University was started in 1958 with