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排序方式: 共有238条查询结果,搜索用时 15 毫秒
1.
A reliability analysis method is proposed in this paper through a combination of the advantages of the response surface method (RSM), finite element method (FEM), first-order reliability method (FORM) and the importance sampling updating method. The method is especially applicable for the reliability evaluation of complex structures of which the limit state surfaces are not known explicitly. After the accuracy and efficiency of the method are demonstrated through numerical examples, the method is used to estimate the flutter reliability of a suspension bridge. The uncertainties such as material properties, geometric parameters, structural damping ratio, flutter derivatives and extreme wind velocity at the bridge site are considered. The example suspension bridge is the Jiang Yin Bridge with a main span length of 1385 m built in China. The results show that the proposed method based on an empirical formula in which the limit state function is explicitly represented as a function of variables overestimates the flutter reliability of suspension bridges. The actual flutter reliability should be more accurately analyzed using the proposed method based on the deterministic finite element method in which the limit state function is implicitly represented as a function of variables. Finally, the most influential random variables on flutter reliability of suspension bridges are identified by using a sensitivity analysis. 相似文献
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近年来,随着风、光电源的大量接入,系统运行的不确定性增大,考虑了系统运行随机因素的随机潮流受到更广泛的关注。提出了一种基于广义多项式混沌法的电力系统随机潮流计算方法。该方法利用广义多项式混沌法的正交多项式逼近思想,将系统的随机性分离至正交多项式基,并利用直角坐标潮流方程的二次性避免非线性潮流方程展开的高阶截断误差,进而利用随机Galerkin法,将随机潮流方程转换为一组确定性方程,通过此方程的求解获得随机潮流状态变量的正交多项式逼近系数,由此系数可获得相关变量的期望和方差,并可结合蒙特卡洛仿真,获得变量的概率密度。IEEE 9节点系统的算例表明,该方法的计算误差大致随多项式逼近阶数的上升而指数下降,通常条件下三阶逼近即可获得较高的精度,具有比蒙特卡洛仿真法更高的计算效率。 相似文献
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为了实现在养殖废水厌氧处理的过程中同时除磷,自行制备改性硅酸钙(MCS),并对其物相和微观进行了表征;随后将其投加到正在运行的厌氧反应装置中,以考察其对养殖废水厌氧处理过程中除磷效果的影响。结果表明:制备的MCS纯度高、粒径小,为半结晶低有序度的水合硅酸钙单相,磷吸附量高达111.04 mg/g。重要的是,MCS的投入不仅未对UASB反应的运行和处理效果产生不良影响,而且可以提高反应器中污泥的活性,并可大幅提高反应器中磷去除率到99.5%,而未投加MCS的对照组中磷去除率仅为50%。 相似文献
4.
Selection of minimal tripping times for distance protection using fault trees with time dependencies
Miroslaw Lukowicz 《Electric Power Systems Research》2011,81(7):1556-1571
Correct coordination between protection relays is an essential requirement to maintain stability and integrity of electrical power systems. Time settings of protection relays have to be adapted to time characteristics of electrical power systems and time settings of other protections. In the paper, fault trees with time dependencies (FTTD) are used for selecting time delay settings of remote back-up distance protections. In FTTD, events and gates are characterized by time parameters, which are derived from time characteristics of protection devices and the inherent delays of protection equipment. Two case studies are presented. First, the coordination of protections for the simple transmission line composed of two identical sections is studied. Next, the transmission line that contains two sections of different lengths and transformer between them is analyzed. In both cases, formulae for time delays of protections are derived. According to calculations executed for the first case, our method gives time delays that often are significantly smaller than values suggested by generally recommended and accepted rules. 相似文献
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Probabilistic assessments in relationship with safety integrity levels by using Fault Trees 总被引:1,自引:0,他引:1
In this article, we study the assessment of safety integrity levels of safety-instrumented system by means of Fault Trees. We focus on functions with a low demand rate. For these functions, the appropriate measure of performance is the so-called probability of failure on demand (PFD) or probability of not functioning on demand. In order to calculate accurately the average PFD as per IEC 61508 standard, we introduce distributions for periodically tested components into Fault Tree models. We point out the specific problems raised by the assessment of safety integrity levels (SILs), which restrict the use of the formulae proposed in the standard. Among these problems there is the fact that SIL should be assessed by considering the time-dependent behavior of the system unavailability in addition to its average value. We check, on a simple pressure protection system, the results obtained by means of the Fault Tree approach against those obtained by means of stochastic Petri nets with predicates. 相似文献
10.
Reliability analysis of solar photovoltaic system using hourly mean solar radiation data 总被引:2,自引:0,他引:2
This paper presents the hourly mean solar radiation and standard deviation as inputs to simulate the solar radiation over a year. Monte Carlo simulation (MCS) technique is applied and MATLAB program is developed for reliability analysis of small isolated power system using solar photovoltaic (SPV). This paper is distributed in two parts. Firstly various solar radiation prediction methods along with hourly mean solar radiation (HMSR) method are compared. The comparison is carried on the basis of predicted electrical power generation with actual power generated by SPV system. Estimation of solar photovoltaic power using HMSR method is close to the actual power generated by SPV system. The deviation in monsoon months is due to the cloud cover. In later part of the paper various reliability indices are obtained by HMSR method using MCS technique. Load model used is IEEE-RTS. Reliability indices, additional load hours (ALH) and additional power (AP) reduces exponentially with increase in load indicates that a SPV source will offset maximum fuel when all of its generated energy is utilized. Fuel saving calculation is also investigated. Case studies are presented for Sagardeep Island in West Bengal state of India. 相似文献