共查询到20条相似文献,搜索用时 0 毫秒
1.
This article deals with the accretion mechanisms of wet snow observed both on a stranded conductor sample in wind tunnel conditions and on real power lines in natural weather conditions. It summarizes the theory and practical observations. Report of experience from France are given in order to demonstrate the efficiency of this passive preventive method based on the increase of torsional stiffness of conductors and to introduce wet snow risk map and countermeasures in France. 相似文献
2.
C. Barbosa A. Francato C. Mariotoni I. Ferreira N. Mascia P. Barbosa 《Engineering Failure Analysis》2011,18(7):1842-1847
The electricity transmission system lines in the Brazilian re-structured market is the subject on this work. Also are studied transmission lines field procedures considering economy and reliability of ACSR (Aluminum Core Steel Reinforced) cables and compression splices. The work describes compression splices field surveys with suppliers and users concessionaires and also suggest some procedures and inspections routines to improve system reliability. 相似文献
3.
4.
覆冰输电线的舞动是一种非线性振动。应用增量谐波平衡法推导了覆冰输电线的有限元分析模型及运动平衡方程,并对舞动方程进行了求解。该方程具有非线性平方及立方刚度项、平方及立方粘滞阻尼项。把振动过程分解成为瞬态的持续增量振动过程,迭代求出舞动频率及振幅,求得方程解的表达式。结合实例分析了输电线舞动的极限环现象和谐波项数的取值问题,与时程积分方法分析结果比较表明吻合较好。对风速增量进行了参数分析推导,算例表明不同风速下覆冰输电线舞动频率与振幅是不同的,在某个临界风速处会发生舞动分岔。 相似文献
5.
6.
C. Klinger M. Mehdianpour D. Klingbeil D. Bettge R. Häcker W. Baer 《Engineering Failure Analysis》2011,18(7):1873-1883
End of November 2005 strong south-west wind and heavy snowfall were predominant in the region Münsterland, north-western part of Germany. This led to accretion of a considerable quantity of wet snow to overhead electrical lines in form of snow rolls on the conductors. Eighty-two transmission towers failed catastrophically, most of them by buckling, however some by brittle fracture. As a consequence nearly 250,000 people have been cut off from electrical power supply for several days with major media attention.This paper describes the forensic analysis in order to investigate the failure cause. Therefore extensive materials investigations, mechanical testing of original components and specimens thereof, estimations for the real wind and snow loads and their combinations, structural analyses as well as detailed evaluations on the basis of previous investigations, literature and regulations were conducted. It was revealed that some of the examined components were manufactured from Thomas steel which was partially in embrittled condition. The investigated towers fulfilled the design codes valid at the time of erection. However the present line loads of the wet snow rolls on the conductors exceeded by far the ones given in the design codes valid at that time.The load case leading to failure was reconstructed by the derived positions of loads mainly caused by unequal and asymmetric distribution of snow rolls on left and right electrical system. The loads and corresponding stresses acting on the structure before failure were estimated. By comparison with the fracture forces from mechanical testing of original members of the collapsed tower the component that primarily failed was localised. The primary fracture occurred on a diagonal member under tension made of Thomas steel which was weakened by embrittlement. The failure cause was a combination of heavy weather conditions (storm, approx. 0 °C and wet snowfall leading to heavy snow rolls on conductors), asymmetric loading conditions and the usage of Thomas steel which was partially embrittled. Finally, recommendations for avoiding future failures are given. 相似文献
7.
8.
作为一种典型的风致敏感结构,大跨越输电线路在强风作用下产生的随机振动张力,往往是线路结构设计中的控制荷载。本文基于导线的连续悬索动力方程和变形几何条件,建立了风振动态张力的广义自由度计算理论模型。依据随机振动理论,获得了动张力响应的功率谱。引入常用的工程设计参数为变量,推导了动张力的均方根反应谱表达式。将其整理和简化,给出了实用设计风荷载的计算公式。以某大跨越输电线路为背景,比较了公式与我国规范、国际电气协会规范取值。结果表明建议公式考虑因素全面,力学意义清晰,结果更为安全合理,可作为规范修订的参考。 相似文献
9.
为了从理论上揭示大跨越高压输电线路覆冰断线的冲击动力响应,针对大跨越高压输电导线分裂布置型式的线路覆冰情况,采用等效单根导线代替分裂导线,利用能量方法,建立了覆冰断线的冲击动力学模型。以某大跨越高压输电线路的一个典型耐张段为例,应用该模型计算了导(地)线覆冰断线和未覆冰断线工况下对铁塔造成的冲击响应,取得了满意的效果。研究表明:覆冰断线造成的冲击动力响应远大于未覆冰断线情况,覆冰断线冲击响应不容忽视。该模型可为大跨越高压输电线路覆冰断线的冲击动力响应试验分析与数值计算提供理论依据 相似文献
10.
11.
12.
13.
为了确保天线系统在发射阶段和入轨工作阶段的安全,对研制的某月球轨道小型星载数传天线进行了振动分析。通过有限元建模仿真方法对该高轨星载天线在发射阶段和入轨工作阶段的振动性能进行了分析和计算,并以此为根据对天线系统结构进行优化设计。进而,通过振动试验对天线系统进行了真实振动环境条件下的测试,结果表明天线系统结构安全。振动试验后对天线电气性能进行了复测,测试结果表明其电气性能稳定,由此验证了天线系统的可靠性和有限元分析的可信性。目前,该数传天线已随星发射并入轨运行,其各项性能指标稳定,工作状态良好。研究结果对提高相关星载天线的振动安全性具有一定的参考作用。 相似文献
14.
15.
16.
利用交指螺旋线结构和枝节贴片设计了一种新型对偶复合左右手传输线结构.采用电磁全波仿真软件和Bloch-Floquet 理论对其进行研究,计算并提取了其色散曲线,研究结果表明该对偶复合左右手传输线结构具有良好的带阻特性,并且阻带内2个传输零点独立可控.在此基础上采用2个单元结构级联的方式设计了一款具有小型化特性的性能优越的带阻滤波器,进行实物加工并使用适量网络分析仪测试,测量结果与仿真结果吻合较好,表明所设计的带阻滤波器中心频率为3.56 GHz,阻带带宽为39.3%,阻带矩形度为0.85,通带带宽为4.47~8.42 GHz,整体性能优越.此外所设计的带阻滤波器整体尺寸为0.237λ×0.145λ(λ为中心频率在自由空间波长),小型化优势明显. 相似文献
17.
Junhua Chen Longmiao Chen Linfang Qian Guangsong Chen Wei Miao 《Quality and Reliability Engineering International》2023,39(1):25-46
Gear systems are widely used in various mechanical transmission systems. This paper aims to develop an effective and practical method for dynamic reliability analysis of gear transmission system. The proposed method can comprehensively evaluate the dynamic reliability of gear transmission system by adopting the fourth-moment SPA method. First, a nonlinear dynamics model of a single-stage spur gear transmission system is established, which simultaneously takes into account the nonlinear backlash, time-varying meshing stiffness, and static transmission error. After that, a dynamic reliability model for the tooth surface contact fatigue failure of gear system is established with the uncertainty of the motion, structure, and material parameters using stress-strength interference (SSI) theory. To be specific, the sparse grid numerical integration (SGNI) method is applied to solve the statistical characteristic parameters of the dynamic reliability of the system. The probability distribution of the performance function is obtained with the fourth-moment SPA method. Test examples show that the results of the proposed method are consistent with the results obtained by the Monte Carlo simulation (MCS) and superior to the maximum entropy with fractional moments (ME-FM) method, which verifies the effectiveness of this approach. Finally, the dynamic reliability of the gear transmission system with respect to load times is evaluated. 相似文献
18.
随着5G等高频信号快速推广和应用,信号上升边沿极速变陡,对汽车控制器的信号完整性造成极大的威胁.针对5G等高频信号对汽车控制器传输线辐射问题,该文对传输线算法模型进行分析,提出一种边界有限元算法模型,该模型能够对汽车控制器的传输线进行边界界定以此进行理论算法曲线分析;针对汽车控制器传输线互连结构造成的辐射问题,提出一种... 相似文献
19.
为研究输电塔结构环境激励下的气动性能,采用特征系统实现算法(ERA)对风洞试验结果进行模态参数识别,提出表征各阶模态脉冲响应振幅的模态参与因子(MPF)作为识别系统模态的参数,利用各阶模态参与因子和相应的特征值推导了模态能量贡献(MEC)的估算公式,利用模态参与因子和模态能量贡献自动提取系统模态以减小识别中的主观影响。比较了试验结果与准定常理论的异同,讨论了气动阻尼与平均风速和风向的关系。结果表明输电塔结构气动阻尼多为正阻尼,顺风向随风速的增大而增大,横风向基本保持定值且未出现负阻尼,气动阻尼与平均风速分量之间存在非线性关系,因而在准定常理论基础上通过引入高阶项对试验结果进行了拟合。 相似文献
20.
针对行星传动装置动态特性复杂、故障率高的问题,拟从动力学角度探索行星传动系统的故障机理。采用改进能量法,仿真分析正常与含裂纹齿轮时变啮合刚度,考虑时变啮合参数影响,运用集中参数法建立了行星齿轮传动系统动力学模型;求解得到了正常与含故障齿轮传动系统动态响应,并对比分析了裂纹故障对动力学特性的影响;通过台架实验,分析了裂纹故障对齿轮动态响应的影响,结合小波分析与EEMD方法对齿轮振动信号进行频谱分析,并对比分析了正常与故障齿轮的频域特性差异,揭示了行星齿轮传动系统的故障机理。研究表明:所建立的动力学模型精度较高,能够很好地描述含故障齿轮传动系统的动力学特性;由于裂纹故障引起传动系统振动的调制效应,导致在齿轮啮合频率附近出现明显边频带,故障齿轮箱的振动能量主要集中在高频段。 相似文献