Current Issue : October - December Volume : 2014 Issue Number : 4 Articles : 5 Articles
In this study, we will cover the basic methods used to distinguish between inrush current and fault\ncurrent in power transformers. First, the nature of inrush current is presented compared to the\nfault current. Then the nature of the magnetizing current due to energizing a power transformer\nat no-load is explained. The first generation of methods used to disable the protective relay system\nduring inrush current, namely the Desensitizing and Tripping Suppressor, is introduced. The\nsecond generation, the harmonic restraint method and the waveform-based restraint method with\ntheir different versions, is explained. Then we will explore thoroughly the fictitious equivalent resistance\nmethod as an example of the third generation of model type restraining or blocking methods.\nFinally, a comparison between these methods and conclusion is carried out....
The Computational Fluid Dynamics (CFD) have been used in the analysis and design of agitated\nvessel. Most of the researches done in this area are limited to the baffled or unbaffled stirred tank.\nIn this paper, we have been interested in studying of the new design. Particularly, the flow and\nturbulence fields in square vessel stirred by a standard Rushton turbine have been simulated by\nmeans of CFD techniques. The Navier-Stokes equations governing the phenomenon of transfer of\nmomentum are solved by a discretization method for finite volume. The MRF approaches can be\nused in simulation of the steady state problem. The numerical results from the application of CFD\ncode Fluent with the stationary approach Multi Reference Frame (MRF) are presented in the\nplanes containing the blade. The validation of CFD results with experimental measurements\nshowed a good agreement....
Blends of acrylonitrile butadiene/ethylene-propylene diene monomer (NBR/EPDM) loaded with different ratios of N-326(HAF)/N-774(SRF) carbon black fillers were prepared. The effects of both blends and N-326/N-774 black ratios on the electrical resistivity were studied. The changes of the electrical resistivity of 50NBR/50EPDM rubber blend during compression were investigated. Based on the shell structure theory, the experimental results were explained from the view that external pressure induces the creation and annihilation of effective conductive paths, leading to the changes in the resistivity of blends....
Natural gas hydrate has tremendous gas storage capacity; natural gas hydrate can be used to store\nand transport energy. The current problem faced is how to improve the hydrate formation rate\nand storage capacity, and form continuously. Compared to the pure water and SDBS solution, the\nionic solution [HMIPS]OTs made by the team was the excellent additive and ensured the best reaction\nconcentration range. Specific effects of different additives on hydrate formation were summarized;\nhydrate formation mechanism of additives was expounded. Considering the investment\ncost, operation cost, simple and stable operation of different surfactants, it is thought that the\nstudy of different additives mechanisms and developing the new efficient additive have the important\nvalue....
According to the Chinese \"Twelfth Five-Year Plan\", two large scale wind farms are planned to be\nbuilt in the shore of Shandong province and Guangdong province to meet the increasing electricity\ndemand with economic development. Before the construction of wind farm, it is necessary to evaluate\nthe wind potential and its temporal variation along the coast of Shandong province, Guangdong\nprovince and Zhejiang province that have been studied in this paper. The data used were\nobtained from Goddard Earth Observing System (GEOS) Data Assimilation System. The results\nshowed that there is rich wind supply in Zhejiang province with small annual variation. Further\naway from shore, the wind energy will increase fastest in Guangdong area. The yield of wind\nenergy in Shandong province is not as rich as in the other two provinces as predicted in the study.\nFurthermore, the layout of wind turbines in wind farm was also investigated to absorb wind\nenergy at the highest efficiency by wind farm. Our results provide a reference for the future construction\nof wind farms....
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