漏电保护器的选用与拒动误动分析

本文首先提出了漏电保护开关的选用与安装施工中的具体要求，提出了运行中可能出现的问题及具体处理方法．同时还分析了漏电保护器拒动与误动的原因及解决方案。     

一起主变差动保护误动事故分析

通过对合肥钢铁公司一起主变压器差动保护误动事故进行详细分析，找出了误动原因，从中吸取了若干经验教训。     

零序保护误动探析

本文通过现场实际操作,对零序保护误动现象进行了探查,分析了误动原因,指明了施工中电缆接地线的正确接法,消除了隐患,保证了供电的可靠运行.     

直流接地系统的危害及具体改进措施

运行实践证明,直流系统接地的危害不仅使继电保护装置误动、拒动,甚至会造成采用直流控制的一次设备误动、拒动,严重危及电力系统安全稳定运行。     

电压互感器开口绕组接线错误导致电压异常的分析

对一起中性点不接地系统中电压互感器开口绕组接线错误导致故障时二次回路电压异常的故障原因进行了分析,指出开口绕组二次线接线错误可能导致系统故障时刻电压互感器保护绕组三相电压不能正确反映故障类型,可能引起保护误动或拒动.对电压互感器开口绕组的接线错误状况进行剖析,并提出了防范措施.     

一起电能质量干扰导致的保护误动事件及应对

就一起实际发生的微机型保护信号传送装置误动事故,对其整改方法、效果、误动原因进行了分析。阐述了一类电压源型干扰导致误动的机理,并讨论了防治方法。     

基于系统合环引起的零序电流保护误动事件的分析及防范

分析了马钢能环部北区两起10 kV系统在合环倒负荷时发生10 kV开关零序保护误动事件的原因,并针对多并电缆运行时电流不平衡问题,提出避免零序保护误动的对策及建议。     

110kV金专线横差保护误动原因分析

介绍了110kV金专线的保护配置及故障时的情况，对横差保护误动原因充分地加以定性分析，并得出相应的合理解释。所存问题在保护复查过程中予以消除，更进一步地提出今后所采取的必要措施和建设性整改意见。     

一起发电机转子接地保护误动引起机组跳闸的事故分析及防范

文章对某发电厂由于发电机转子接地保护误动引起机组跳闸的事故过程及原因进行了分析,并对暴露的问题提出了改进和防范措施.     

特殊直流接地故障处理分析

某电厂3#机组主厂房直流系统I段、II段母线,自投入运行两年以来正极一直绝缘不良,发生不完全接地,而且有逐渐上升的趋势,如果不及时选除,存在电气系统保护的拒动或误动的风险;两段直流同时绝缘不良,选除的难度大、风险也大,处理不当同样会使保护拒动或误动,进而引发机组跳闸事故。针对这种情况,通过对系统负荷及运行实况的全面分析研究后,找到了一种不影响机组运行,安全稳定的接地选除方法,及时避免了直流接地保护误动,引发机组跳闸的非计划停机。     

Thermal Cracking of Viscoelastic Asphalt-Concrete Pavement

This paper studies the thermal cracking of asphalt-concrete pavements using a semianalytical model that accounts for the multiscale nature of the thermal cracking phenomenon, the viscoelasticity of asphalt-concrete, and the frictional constraint on the pavement interface. This paper extends previous work to include the effects of asphalt-concrete viscoelasticity and to include a study of the effects of the major parameters. Numerical simulations lead to almost uniformly spaced thermal cracks, similar to field observations of real flexible pavement structures. A parameter study shows that material homogeneity, asphalt-concrete ductility, frictional constraint on the interface, and rate of cooling significantly influence the thermal cracking of asphalt-concrete pavements.     

锌及锌铝合金热喷涂涂层的腐蚀防护研究

锌及锌铝合金热喷涂涂层可以最大限度地为钢结构件和混凝土中的钢筋提供腐蚀防护。锌及锌铝合金热喷涂涂层主要的加工方式为电弧喷涂和火焰喷涂,可以在基体表面形成密封层,这就产生了一个最佳的被动与主动相结合的腐蚀防护体系,使得工件的使用寿命延长到20年。本文研究了锌及锌铝合金热喷涂涂层的微观属性和接近实际工况时的腐蚀防护特点。     

Thermal Stresses in Spherical Shells

This paper presents an iterative finite-difference technique for the analysis of axisymmetric spherical shells with variable wall thickness. The formulation is based on thin elastic shell theory. One-dimensional finite-difference points are used to discretize the shell into strips along the meridian, and an iterative technique is employed to determine the normal and meridional displacements. The stress resultants and bending stresses are then evaluated. Unlike existing analytical and finite-difference techniques, the proposed method is applicable with ease to any variation in rigidity along the meridian, to general loading conditions, and to steep and shallow shells. Results are presented and compared with those of the finite-element method.     

Thermal stability of finely dispersed ferromagnetic powders

The oxidation mechanism and kinetics have been examined for finely dispersed powders of iron and compounds containing it and noble and platinum metals; these powders were made by a thermochemical method and examined at 20–400°C. The powders do not change in composition and magnetic characteristics up to 110°C because the surfaces of the particles are protected by iron oxides and carbide. This allows the powders to be used to make materials for medical purposes, since they can be sterilized at that temperature. Translated from Poroshkovaya Metallurgiya, Nos. 5–6(413), pp. 1–4, May–June, 2000.     

Economic Analysis of Thermal Energy Storage Systems

This paper describes an investigation of the economic performance of a central chiller plant with thermal energy storage (TES) operating in a hotel in California and an office building in Wisconsin for the following three conventional control strategies: chiller-priority, constant-proportion, and storage-priority control. Since all control strategies depend on properly selected design parameters, the storage and chiller capacities as the primary design parameters were varied over a wide range, and the life-cycle economic feasibility of each possible design was assessed over a 20-year economic life using the net present value method. Measured cooling and weather data for both buildings were used in annual calculations to determine annual utility cost savings on the basis of one of four artificial rate structures. Trends in the life-cycle economic performance of TES systems as a function of chiller and storage capacities were revealed, and design guidelines were developed.     

陶瓷蜂窝蓄热体的热应力分析

分析了高风温燃烧系统中陶瓷蜂窝蓄热体和气体间的热量交换,建立了陶瓷蜂窝蓄热体传热过程数学模型。对于由温度分布不均匀,陶瓷蓄热体膨胀或收缩受限制而产生的热应力进行了计算和分析,其结果为蓄热式高风温燃烧系统的设计及运行参数的选择提供了理论依据。     

提高锅炉热效率的方法

本文介绍了提高锅炉热效率的一些方法,通过采用均匀分层燃烧装置、改善配风、防止结焦、减少排烟散热损失和加强运行管理获得了一些效果。     

Thermal oral-pharyngeal stimulation and elicitation of swallowing

Anaplastic thyroid carcinoma is one of the most lethal neoplasms, with poor prognosis being reported by most authors. The benefits of surgery for most cases of advanced disease remain controversial. In this study we asked the following question: Does surgical intervention alter outcomes for patients with advanced anaplastic thyroid carcinoma? Forty-six patients with advanced anaplastic thyroid carcinoma were analyzed. There were 20 patients with advanced localized disease (group 1), 15 of whom received surgery. Of the other 26 patients with evidence of distant metastases (group 2), 13 received surgery. For group 1 patients, the mean survival was 12.8 months versus 8.6 months in the surgical and nonsurgical subgroups (p = 0.46). For group 2 patients, the mean survival was 3.5 months versus 2.8 months in the surgical and nonsurgical subgroups (p = 0.72). These data suggest that surgery does not improve survival for patients with advanced anaplastic thyroid carcinoma. In conclusion, the mean survival showed no significant differences between surgical and nonsurgical patients (p = 0.43). This study suggests that surgical resection does not improve the survival of patients with advanced anaplastic thyroid carcinoma.     

Thermal Ice Growth: Real-Time Estimation

The quasi-steady thermal ice growth model was recast in state-space form and used with the Kalman filter to estimate ice thickness and to recursively estimate the model parameters for thermal ice growth. This approach was appropriate at locations where measurements of the ice thickness were made during the study. The model was applied to two widely separated sites from which ice thickness measurements were available for a number of winters: Post Pond, N.H., and Snowshoe Lake, Alaska. The parameters required by the Kalman filter were estimated through numerical experiments and were consistent between both locations. The Kalman filter was able to produce better results, as measured by a least-squares criterion, than a model using parameter values that had been determined using all data at each location.