Evaluation of wind load integration in disproportionate collapse analysis of steel moment frames for column loss

The design of steel structures, in most cases, depends majorly on the level of wind loads which are prescribed by codes and regulations and are used in the structural analysis due to the fact that steel structures being light and ductile systems are strongly affected from a slight difference in the values of wind loading. During the last decades, disproportionate collapse analysis has become of major interest mainly due to the increasing number of failures occurring in that pattern. Commonly accepted guidelines and methods of analysis have been produced, the most dominating of which being the Department of Defense Facilities criteria or DoD. In the DoD, as well as in other criteria, the event of a column loss is suggested as the modeling scenario which has to be sustained by a structural system in order to be robust. However, all the guidelines so far have disconnected the column loss analysis from wind loads and have only performed it for gravity loading. This paper presents the dynamic time history disproportionate collapse analysis of steel frames, including various levels of wind loading. Interesting aspects are discussed through the parametric analysis of five different numerical examples of moment resisting frames.     

Experimental investigation on a parabolic trough solar collector for thermal power generation

Developing solar thermal power technology in an effective manner is a great challenge in China.In this paper an experiment platform of a parabolic trough solar collector system(PTCS) was developed for thermal power generation,and the performance of the PTCS was experimentally investigated with synthetic oil as the circulate heat transfer fluid(HTF).The solar collector's efficiency with the variation of the solar flux and the flow rate of the HTF was identified.The collector efficiency of the PTCS can be in ...     

PWM激励下异步电机铁耗等值电阻模型

通过分析PWM激励下异步电机铁耗变化的特点,提出了一种综合考虑电机运行工况和PWM波形特性的铁耗等值电阻模型。基于铁耗分离原理,使用三个电阻分别等效电机铁耗的磁滞分量、经典涡流分量和异常涡流分量,并推导了正弦激励下各个电阻分量的表达式;进而通过分析PWM激励与正弦激励下铁耗间关系,对正弦激励下铁耗模型进行修正,获得PWM激励下铁耗模型;最后提出了确定该模型参数的实验方案。所建模型中各个电阻分量随电机运行频率和PWM波形的调制系数变化而变化,且变化规律各不相同,提高了电机铁耗计算的准确性。仿真和实验验证了该模型的正确性和有效性。     

Power loss minimization considering short‐circuit capacity in distribution system with decentralized distributed generation

In the future, a large number of distributed generators are expected to be connected to the distribution system. However, with the connected capacity of distributed generation (DG) increasing, the problems of short‐circuit capacity (SCC) over the interrupting capacity of the circuit breaker (CB) and power loss increases due to reverse power flow from DG are inevitable. In this paper, a reconfiguration methodology based on an optimal algorithm is applied to the distribution system with DG to minimize power loss, taking into account the SCC. Moreover, in order to further reduce the loss, the daily load variation is also considered and the optimal model decided by calculations. Finally, to illustrate its application, the methodology is applied to a case study of a 33‐bus system with decentralized DG units. The results show that this method is obviously able to reduce power loss and make the network operate in the optimal mode with normal load variation, at the same time decreasing the SCC within the interrupting maximum of the faulty CB. Moreover, the whole voltage profile is also improved. © 2012 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

240MVA/220kV双绕组升压变压器工艺系数分析

对几台240MVA/220kV双绕组升压变压器的空载损耗、空载电流和短路阻抗这几个重要参数的试验数据和设计计算值进行了比较与分析,得出了这些参数的一些经验系数.     

东北电网水电站水能利用情况分析

由于每一座水电站的情况不同,用耗水率很难对各水电站之间的水能利用情况进行比较,本文用“水能利用效率”对东北电网水电站的水能利用情况进行比较和分析,11座水电站多年平均水能利用效率为82．8％,堤坝式水电站高于引水式和混合式水电站,较客观地评价了各水电站的水能利用情况。     

高压供电计量方式的选择

根据目前高压供电局计量方式的实际情况,本文对比分析了高供高计以及高供低计这两种高压供电方式的特点,并从经济性、维护的便捷性以及变损的计算等方面,明确了高供高计以及高供低计的适用范围,并为选择合理的高压供电计量方式提供指引.     

冰箱门封导热性能及影响因素的CAE分析

由于冰箱门封对于节能非常重要,本文利用CAE仿真技术,采用二维平面模型对多款冰箱门封进行仿真研究,为冰箱门封和冰箱的性能设计和优化提供理论依据。通过对典型冰箱门封导热性能的分析,找出影响门封导热性能的因素,同时,以某型号冰箱为例,研究门封对冰箱漏冷量的影响。仿真结果表明,门封结构及磁条是门封导热性能的重要因素;门封等效导热系数约为0.05W/(m·K);冰箱门封漏冷占冰箱总漏冷约8%;门封高度从10mm减小为7mm时,冰箱门封漏冷比率减小约2.3%。     

基于拓扑分析的电能表编码方法

提出了一种基于拓扑分析的电能表编码方法,该方法将电能表所在网络的拓扑结构进行编号,并与传统的电能表编码组合,形成新的编码体系。这样的编码不但能反映电能表自身的相关属性,而且能通过与自动抄表系统的配合反映电能表所在网络拓扑结构的变化,从而消除由于运行方式变化带来的线损计算误差。     

一类输电网损分摊方法的积分路径相关性简析

利用功率微增量进行求和是目前输电损耗分摊中的一类代表性方法。文中讨论了该类方法所存在的积分路径相关性问题,表明等步长划分积分区间本身即是一类特殊且并无明显理论依据的求和(积分)路径,至少到目前为止,尚无相关理论可以支持这类特解在理论体系上的恰当性。对该类方法而言,如何克服其所存在的求和路径相关性问题仍然是一个开放的、有待解决的问题。