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Crowdsourcing systems allocate tasks to a group of workers over the Internet, which have become an effective paradigm for human-powered problem solving, such as image classification, optical character recognition, and proofreading. In this paper, we focus on incentivizing crowd workers to label a set of multi-class labeling tasks under strict budget constraint. We properly profile the tasks’ difficulty...
Although it has been found that the insulating characteristics of thermal bubble induced two-phase flow changes with pressure and heat power, its breakdown mechanism has not been known clearly so far. In order to obtain actual working conditions of two-phase flow state of fluorocarbon, a special apparatus with self-heating plane-plane electrodes is fabricated to study the relation of AC breakdown...
The growing rated capacity of gas insulated transformers (GIT) are confined by the limitation of cooling capability. Hence a new thermal relay transmitted cooling system was applied in GIT and presented in this paper. The whole cooling system consists of conventional heat pipes and loop heat pipe (LHP): Dozens of non-metallic conventional heat pipes are distributed in the windings, absorbing heat...
Because of its high dielectric strength, good partial discharge capability, low global warming potential (GWP), none ozone depletion potential (ODP) and non-toxicity, fluorocarbon gas is a possible substitute for SF6 gas, and can be used hopefully in electrical equipment, such as GIL, C-GIS. Arc voltage and potential gradient are useful in arc modeling and computational investigation of gas insulated...
Decades of experience in underground substations indicated that the traditional cooling technologies have their own various shortcomings. Therefore, a novel evaporative cooling system was pointed out and will be applied in a power transformer of an urban substation. This new cooling technology could be considered as a two-step cooling system, which could transport heat energy effectively from underground...
Evaporative cooling transformer, using inflammable fluorocarbon liquid as insulation medium and coolant, is suitable for some special applications in utilities. However, the fluorocarbon liquid is so expensive that the evaporative cooling transformer must be developed economically with effective method to save the coolant cost. A preliminary study for exploring the configuration of evaporative cooling...
The distribution power transformers with amorphous alloy cores are used to employing the core type structure since they were developed, which results in higher noise level and poorer short circuit withstanding ability. To explore the countermeasures for above challenges, the shell type power transformers with amorphous alloy cores are presented. A new type of clamp is designed to withstand the huge...
Because of its high-capacity, low losses and no electromagnetic interference, the gas-insulated transmission line (GIL), which is a replacement of an overhead line in special environments, has been used for over 40 years, mainly as bus ducts of gas-insulated substations or underground connections in power plants. The insulated and cooling gas in GIL is mainly SF6 or its mixtures, which have high global...
Decades of experience in underground substations indicated that the traditional cooling technologies have their own shortcomings. Therefore, a novel Oil-Evaporative liquid cooling technology is presented. This new cooling technology could be considered as a two-step cooling system, which could effectively transport heat energy from thermal sources underground to radiators on the ground by phase changing...
As the increasing demand for large capacity, high voltage and high reliability power transformers in urban power grid, oil-free, non-flammable and non-explosive equipment is recommended. For this reason, evaporative cooling transformers, gas insulated transformers and other electrical equipment using fluorocarbon as coolant and dielectric have been developed. This paper presents an experimental survey...
Because of its high dielectric strength, good partial discharge capability, low global warming potential (GWP), none ozone depletion potential (ODP) and nontoxicity, fluorocarbon gas is possible substitute for SF6, and can be used hopefully in electrical equipment, such as circuit breaker. In this paper, we calculate the pressure characteristic of circuit breaker using gas mixture containing fluorocarbon...
Because of its high dielectric strength, good partial discharge capability, low global warming potential (GWP), none ozone depletion potential (ODP) and nontoxicity, fluorocarbon gas is possible substitute for SF6, and can be used hopefully in electrical equipment, such as circuit breaker. In this paper, we calculate the pressure characteristic of circuit breaker using gas mixture containing c-C4F...
Although the amorphous alloy core power transformers have the advantage of lower core loss, the high noise level and weak short-circuit strength are inevitable. To explore the countermeasures for noise decreasing, an amorphous alloy core model was employed for detailed experimental study. A large number of noise measurements (A-weighted sound pressure level) were implemented by changing magnetic flux...
SF6 gas has been widely used currently in electric power systems, such as GIS, GIL and GIT. However, because of the high global warming potential (GWP), SF6 was listed as one of the six restricted gases in "Kyoto Protocol" in 1997. Some fluorocarbon gases with low environmental effect and high dielectric performance are studied as the substitution candidates for SF6. This paper presents...
This paper describes the partial discharge (PD) performances of gas mixtures with small fluorocarbons because their global warming potential (GWP) is smaller than that of SF6 gas, which was regulated as one of six restricted gases. It is difficult to apply pure fluorocarbon gases as insulating medium directly in gas insulated switchgear (GIS) and gas circuit breakers (GCB), because their liquefying...
Because of the high global warming potential (GWP), SF6 gas was listed as one of the six restricted gases in 1997. Some fluorocarbon gases with low environmental effect and high dielectric performance are studied as the substitution candidates for SF6. This paper presents the partial discharge (PD) capability of some gas mixtures with fluorocarbon at different pressures and ratio of fluorocarbon in...
Evaporative cooling power transformers with perfluoro-carbon as coolant and dielectric is a new kind of power transmission and distribution equipment. To lay the foundation for safety operation and maintenance, as well as fault diagnosis, an overheating experimental model of perfluorocarbon in the two-phase flow was designed, the decomposition products were analyzed by means of gas chromatography/mass...
The AC breakdown voltages of a fluorocarbon were measured under three states, including in gaseous state, in boiling two phase flow state and in liquid state. Because the insulating medium in two phase flow could be used in some electrical apparatus, the author measured the breakdown voltage of two phase flow under various pressures in the vessel, various water contents in the coolant. The results...
As some fluorocarbons have the nonflammability and high electrical strength, they could be used not only as coolant, but also as insulating materials. In order to obtain the AC breakdown voltage of some fluorocarbons under two-phase- flow condition, special experimental equipment was designed and fabricated. Using a plane-plane electrode with a gap length of 3 mm, the test was carried out and the...
The measurement and analysis of the relative permittivity and the dielectric dissipation factor of an insulating fluid were presented. An instrument was updated and modified for its suitable measuring in three phases, including gas-liquid two phase flow, gaseous and liquid flow. Using this equipment, the relative permittivity and the dielectric dissipation factor of a fluorocarbon were measured at...
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