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广域保护中基于能量守恒原理的母线及输电线差动保护 总被引:3,自引:3,他引:0
提出一种基于能量守恒原理的纵联差动保护,对线路两端或母线各端的有功功率进行比较,若各端功率的和超出整定值,则判定为区内故障。在典型400 kV输电系统模型上,运用MATLAB仿真软件对所提出的原理进行了仿真验证。仿真结果表明,该方法比传统电流比率差动保护更加可靠且计算量小,因而可缩短动作时间。该方法能检测所有故障类型,适应于超高压远距离输电线路。 相似文献
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Stéphane Bressan Alfredo Cuzzocrea Panagiotis Karras Xuesong Lu Sadegh Heyrani Nobari 《Journal of Parallel and Distributed Computing》2013
The widespread usage of random graphs has been highlighted in the context of database applications for several years. This because such data structures turn out to be very useful in a large family of database applications ranging from simulation to sampling, from analysis of complex networks to study of randomized algorithms, and so forth. Amongst others, Erd?s–Rényi Γv,p is the most popular model to obtain and manipulate random graphs. Unfortunately, it has been demonstrated that classical algorithms for generating Erd?s–Rényi based random graphs do not scale well in large instances and, in addition to this, fail to make use of the parallel processing capabilities of modern hardware. Inspired by this main motivation, in this paper we propose and experimentally assess a novel parallel algorithm for generating random graphs under the Erd?s–Rényi model that is designed and implemented in a Graphics Processing Unit (GPU), called PPreZER. We demonstrate the nice amenities due to our solution via a succession of several intermediary algorithms, both sequential and parallel, which show the limitations of classical approaches and the benefits due to the PPreZER algorithm. Finally, our comprehensive experimental assessment and analysis brings to light a relevant average speedup gain of PPreZER over baseline algorithms. 相似文献
15.
Polymerization of propylene was performed using MgCl2. EtOH.TiCl4.ID.TEA.ED catalyst system in hexane, where internal donor (ID) was an organic diester and external donor (ED) was a silane compound and also triethyl aluminum (TEA) as activator. A new method called isothermal/nonisothermal method (INM), a combination of isothermal and nonisothermal methods, was applied to produce the spherical polymer particles. The effects of the INM method and prepolymerization temperature on the final polymer morphology, Mw, and catalyst activity were also investigated. The morphology of the polymers was evaluated through scanning electron microscopy (SEM) images. GPC results were used for molecular weight (Mw) evaluation. It was found that the polymers had a better morphology when they were prepared using INM method. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009 相似文献
16.
Mostafa Rajabi Mashhadi M. Hossein Javidi D. B. M. Sadegh Ghazizadeh 《Electrical Engineering (Archiv fur Elektrotechnik)》2011,93(3):117-126
Frequency control, as an ancillary service, is usually provided by generation reserves. Modern generating units have special
technical capabilities; e.g., their governor operation mode can be selected to be either active or passive, their ramp rate
can be selected to be either normal or fast, etc. On the other hand, generating units have some technical constraints; e.g.
some generating units cannot participate in primary frequency control at their capacity limits. In this paper, operational
capabilities and constraints of generating units are incorporated in a “simultaneous scheduling of energy and primary reserve”
problem. Furthermore, a heuristic iterative method (based on genetic algorithm) is proposed to obtain the optimal scheduling.
The impacts of capabilities and constraints on scheduling are investigated through simulation studies. Simulation results
depicts that taking these capabilities and constraints of generating units into account, not only reduces the total operational
cost of generating units, but also will end up with a feasible solution for the system, even in cases where the previously
proposed methods fail. 相似文献
17.
In recent years, uneven distribution of available water resources as well as increasing water demands and overexploiting the water resources have brought severe need for transferring water from basins having sufficient water to basins facing water shortages. Therefore, optimal allocation of shared water resources in water transfer projects, considering the utilities of different stakeholders, physical limitations of the system and socioeconomic criteria is an important task. In this paper, a new methodology based on crisp and fuzzy Shapley games is developed for optimal allocation of inter-basin water resources. In the proposed methodology, initial water allocations are obtained using an optimization model considering an equity criterion. In the second step, the stakeholders form crisp coalitions to increase the total net benefit of the system as well as their own benefits and a crisp Shapley Value game is used to reallocate the benefits produced in the crisp coalitions. Lastly, to provide maximum total net benefit, fuzzy coalitions are constituted and the participation rates of water users to fuzzy coalitions are optimized. Then, the total net benefit is reallocated to water users in a rational and equitable way using Fuzzy Shapley Value game. The effectiveness of this method is examined by applying it to a large scale case study of water transfer from the Karoon river basin in southern Iran to the Rafsanjan plain in central Iran. 相似文献
18.
Hossein Ebrahimnezhad-Khaljiri Reza Eslami-Farsani Sadegh Mirzamohammadi 《应用聚合物科学杂志》2023,140(1):e53273
In the current study, the effect of adding the encapsulated healing agent with neat polymeric and nanocomposite shells on the mechanical-healing features of glass fibers/epoxy composite under various loads was investigated. Therefore, the microcapsules with urea-formaldehyde (UF) nanocomposite shell containing the various weight fraction of silica nanoparticles (0, 1, 2, 3) were synthesized. After that, the flexural, tensile, and interlaminar shear strength (ILSS) samples were destructed by using the quasi-static penetration method with the damaging force of 500, 1050, and 2900 N, respectively. The maximum healing efficiency in the flexural loads belonged to the composite with the 3 wt% nanosilica on the surface of microcapsules, which was 83.9%. Also, it was found the increment in the weight fraction of silica nanoparticles had a negligible effect on the healing ability of composite under tensile loading. Achieving 135.8% healing efficiency in the composite with the 2 wt% nanosilica under the shear loads can be one of the most important findings in this work. 相似文献
19.
Mohammad Sadegh Valipour Ariyan Zare Ghadi 《International Communications in Heat and Mass Transfer》2011,38(9):1296-1304
In this study, flow-field and heat transfer through a copper–water nanofluid around circular cylinder has been numerically investigated. Governing equations containing continuity, N–S equation and energy equation have been developed in polar coordinate system. The equations have been numerically solved using a finite volume method over a staggered grid system. SIMPLE algorithm has been applied for solving the pressure linked equations. Reynolds and Peclet numbers (based on the cylinder diameter and the velocity of free stream) are within the range of 1 to 40. Furthermore, volume fraction of nanoparticles (φ) varies within the range of 0 to 0.05. Effective thermal conductivity and effective viscosity of nanofluid have been estimated by Hamilton–Crosser and Brinkman models, respectively. The effect of volume fraction of nanoparticles on the fluid flow and heat transfer characteristics are investigated. It is found that the vorticity, pressure coefficient, recirculation length are increased by the addition of nanoparticles into clear fluid. Moreover, the local and mean Nusselt numbers are enhanced due to adding nanoparticles into base fluid. 相似文献
20.
Mohammad ZareKhafri Fahimeh Alizadeh Sadegh NouripourSisakht Alireza Khodavandi Majid Gerami 《IET nanobiotechnology / IET》2020,14(5):375
Fluconazole‐resistant Candida albicans is a big scary reality. The authors assessed the antifungal effects of magnetic iron‐oxide nanoparticles on fluconazole‐resistant colonising isolate of C. albicans and determined the expression of ERG11 gene, protein sequence similarity and ergosterol content. C. albicans isolates were characterised and fluconazole resistance is recognised using World Health Organization''s WHONET software. Susceptibility testing of magnetic iron‐oxide nanoparticles against fluconazole‐resistant colonising isolate of C. albicans was performed according to Clinical and Laboratory Standards Institute guidelines. The expression patterns of ERG11 and protein sequence similarity were investigated. Ergosterol quantification has been used to gauge the antifungal activity of magnetic iron‐oxide nanoparticles. The findings indicated that 93% of C. albicans isolates were resistant to fluconazole. Magnetic iron‐oxide nanoparticles were presented activity against fluconazole‐resistant colonising isolate of C. albicans with minimum inhibitory concentration at 250–500 µg/ml. The expression level of ERG11 gene was downregulated in fluconazole‐resistant colonising isolate of C. albicans. The results revealed no differences in fluconazole‐resistant colonising isolate of C. albicans by comparison with ERG11 reference sequences. Moreover, significant reduction was noted in ergosterol content. The findings shed a novel light on the application of magnetic iron‐oxide nanoparticles in fighting against resistant C. albicans.Inspec keywords: microorganisms, biochemistry, molecular biophysics, antibacterial activity, iron compounds, proteins, cellular biophysics, nanoparticles, drugs, geneticsOther keywords: albicans isolates, magnetic iron‐oxide nanoparticles, fluconazole‐resistant colonising isolate, fluconazole resistance, ERG11, candida albicans, protein sequence similarity, ergosterol content, WHONET, ergosterol quantification, susceptibility testing, antifungal activity, gene expression 相似文献