Modified routine for decreasing numeric oscillations at associations of lumped elements

Some changes in the application of the numeric trapezoidal integration are analyzed for applications considering pi circuits. It is considered numeric and computational proceedings for improving the numeric results obtained with associations of pi circuits. In numeric integration solutions of the linear systems, it is common to represent these associations of pi circuits by only one matrix. This representation introduces undesirable numeric oscillations in simulations of the dynamics of wave propagation in electrical systems. The proposed changes improve the results of application of cascades of pi circuits associated to the trapezoidal integration, avoiding that the numerical oscillations, or Gibb's oscillations, have high values and are slowly damped. For the carried out simulations, different number of pi circuits and voltage sources are checked, confirming the reduction of the influence of the numeric oscillations on the obtained results. (C) 2014 Elsevier B.V. All rights reserved.

Comportamento dinâmico não-linear em fenômenos de colheita de energia usando dispositivos baseados em materiais piezoelétricos em estruturas aporticadas

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Teorias de potência conservativa e instantânea: análise comparativa

Pós-graduação em Engenharia Elétrica - FEB

Diagnóstico de distúrbios de tensão em sistemas de distribuição de energia elétrica usando um algoritmo imuno-neural

Pós-graduação em Engenharia Elétrica - FEIS

Fitting the frequency-dependent parameters in the Bergeron line model

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Energetic and economic analysis of a Brazilian compact cogeneration system: Comparison between natural gas and biogas

Cogeneration may be defined as the simultaneous production of electric power and useful heat from the burning of a single fuel. This technique of combined heat and power production has been applied in both the industrial and tertiary sectors. It has been mainly used because of its overall efficiency, and the guarantee of electricity with a low level of environmental impact. The compact cogeneration systems using internal combustion engine as prime movers are thoroughly applied because of the good relationship among cost and benefit obtained in such devices. The cogeneration system of this study consists of an internal combustion engine using natural gas or biogas as fuel, combined with two heat exchangers and an absorption chiller utilising water-ammonia as working mixture. This work presents an energetic and economic comparison between natural gas and biogas as fuel used for the system proposed. The results are useful to identify the feasible applications for this system, such as residential sector in isolated areas, hotels, universities etc. (C) 2014 Elsevier Ltd. All rights reserved.

Transmission Expansion Planning Via a Constructive Heuristic Algorithm in Restructured Electricity Industry

The transmission expansion planning problem in modern power systems is a large-scale, mixed-integer, nonlinear and non-convex problem. this paper presents a new mathematical model and a constructive heuristic algorithm (CHA) for solving transmission expansion planning problem under new environment of electricity restructuring. CHA finds an acceptable solution in an iterative process, where in each step a circuit is chosen using a sensitivity index and added to the system. The proposed model consider multiple generation scenarios therefore the methodology finds high quality solution in which it allows the power system operate adequacy in an environment with multiple generators scenarios. Case studies and simulation results using test systems show possibility of using Constructive heuristic algorithm in an open access system.

Congestion Effects on Regional & System Emission and Consumers Allocated Cost

This paper considers the congestion effects on emission and consumers' allocated cost. In order to consider some environmental and operational effects of congestion, an environmental constrained active-reactive optimal power flow (AROPF) considering capability curve is presented. On outage conditions, the total cost of the system will increase. On the other hand in power systems, the operating cost and system emission have conflicted objectives, then it may be concluded that the outage in the system may lead to a total emission decrease. In this paper the famous Aumann-Shapley method is used as a pricing methodology. Two case studies such as 14-bus and US-bus IEEE test systems are conducted. Results demonstrate that, although the line outage in power systems leads to increase the total cost, the amount of emission depending on the place where the outage occurs can be more than, less than or equal to the normal conditions' emission. Also results show that although from power sellers' standpoint the well-known Aumann-Shapley method is a precise pricing method to cover the incurred cost with an acceptable error that can show the real effect of congestion on consumers' cost, from consumers' standpoint it is not a good method for cost allocation, because some consumers will face with an increase in cost and the others will face with a decrease on their cost.

Avaliação da influência dos parâmetros de processo de soldagem MIG no surgimento de poros em tubos de alumínio

The process of electric arc welding with shielding gas (GMAW) is being increasingly used in various industrial applications. This process occurs by which an electric arc is established between the work piece and a consumable in the form of wire, the arc melts the wire continuously as it is fed to the weld pool. The weld metal is protected from the atmosphere by flowing a gas (or gas mixture) inert or active. This paper presents a study of the welding process GMAW - MIG on aluminum tubes, alloy 6101 - T6, used in the manufacture of armored busbar, intended for driving electric power plants. 5(five) were welded specimens, changing certain welding parameters at each time was monitored welding joint as well as the interpass temperature. Tests were performed bending, tensile and macrographical analysis of body-of-evidence and through its results was possible to reach a better welding condition, which minimizes the appearance of pores, since the porosity has great influence on the mechanical strength and electrical conductivity of welded pipes

Seleção de motobombas para o setor sucroalcooleiro

This work has the purpose to explain how the sugar and alcohol sector works, detail all the processes which uses pumps and assist in the selection and specification of pumps attached with engines, that will make part in important industry processes in the manufacture of sugar and alcohol. A bibliographic revision about the working of sugar and alcohol sector and about pumps were made to help the analysis of a case. This case had the purpose to analyze the selected pumps that were part of a initial project of an industry which aimed a future expansion. The pumps that were selected to made part of the initial project were over dimensioned and were operating out of the best performance point, making the pumps inefficient because the expansion didn't happened. The solution was to select another pump with bigger performance and less power consumption to have a decrease in the energy consumption and in the operational costs of the industry and using the extra electric energy in the industry or selling it

Estudo e analise dos sistemas de proteção em subestações automatizadas de energia elétrica

Electrical energy is present in the lives of all people and is extremely important that it be delivered to end users with plenty of quality, safety and low costs. The electric power substations are responsible for transmission and distribution of electricity generating sources to consumers, and with technological advances and the subsequent automation of same, the electricity began to be delivered with greater continuity and reliability. Protection systems in substations are largely responsible for making the electricity reaches the final consumer with quality, since their function is to prevent the spread of any type of failure occurred at any point of transmission to the load centers. These systems consist primarily by the current transformers and potential, by the protective relays and circuit breakers and switchgear. The processors send the necessary data to the relays and, if those detect any abnormality in the system, operate the opening command of the branch circuit breakers to isolate where the fault. Therefore, it is essential to better understand the operation of such equipment, as well as the overall system. This work aims to study the main substation equipment, current transformers and potential and, especially, protection relays, in order to obtain the advantages that automated systems can provide

Análise da viabilidade de motorização elétrica do soprador no ciclo regenerativo da unidade de craqueamento catalítico fluidizado em uma refinaria

One of the biggest environmental problems of today is the climate change. Experts affirm that this global warming is related to the greenhouse effect. Its causes are directly related to human activity, especially the use of fossil fuels. In this context, companies around the world are challenged to improve energy efficiency in order to reduce the environmental impact and work toward the so-called tripod of sustainable development that focuses on the social, economic and environmental aspects of a business strategy. The first step a company can make in this regard is to conduct an inventory of emissions of greenhouse gases (GHGs). The reduction of GHG emissions in a refinery can be achieved by replacing steam turbines with electric motors to drive big machines, this reduction is achieved by relieving the steam consumption for electric power available or purchased. An important aspect associated with the reduction of GHG emissions is the best performance of the Energy Intensity Index (ERI). The objective of this study was to analyze the feasibility of the blower motorization in the regenerative cycle of a fluidized catalytic cracking unit at a specific refinery. For development work, two methods were used, the initial screening and optimization scenarios with the help of software Butyl. The results indicate that after a certain cost of natural gas this substitution becomes favorable. In addition, there is a large reduction of CO2 emissions avoided by burning fuel

Incorporação de um sistema nobreak com ultracapacitor em um microcomputador

The objective of this work is to analyze the viability of incorporation in a microcomputer box of a nobreak with an ultracapacitor as energy storage device, substituting the conventional chemical battery. An advantage of this inclusion is cost reduction because a specific metallic or plastic frame won’t be necessary to protect the components of the nobreak; the microcomputer metallic frame offers the necessary protection for both equipments. Moreover, a large quantity of internal space of microcomputers box isn’t used, and is possible to use it to wrap up the nobreak. This work uses data about average power consumption of microcomputers; operation of switching mode power supplies for microcomputers; electrical and mechanical characteristics of ultracapacitors and operation of power circuits of nobreaks, with the purpose of present a study of energy storage capacity that an ultracapacitor should have to allow a safe switching off of a microcomputer in case of electrical network fail. It was noticed that the use of ultracapacitors is feasible to feed an 180 W load for 75 s, using a capacitive bank with sixteen ultracapacitors, with a total capacitance of 350 F and voltage of 10,8 V. The use of the proposed nobreak increases the reliability of the microcomputer by reducing the probability of user data losses in case of an electrical network fail, offering a high cost/benefit product. The substitution of the battery by an ultracapacitor allows a quick nobreak recharge, with low maintenance costs, since ultracapacitors have a lifetime bigger than batteries; beyond reducing the environmental impact, because they don’t use potentially toxic chemical compounds

Estudo comparativo entre subestações ao tempo e subestações isoladas a gás

In this paper are compared two methods of deploying electrical substations, conventional type, when installed at open areas (Air Insulated Switchgear - AIS), and compact gas-insulated (Gas Insulated Switchgear - GIS) when installed inside buildings. With the expansion of urban centers, areas available for deployment of conventional substations become increasingly difficult to find in these locations. Also due to speculation in urban areas, it becomes feasible to install Gas Insulated Switchgear. This paper presents and evaluates criteria with advantages and disadvantages for application of the two methodologies, aiming to assist in decisionmaking moment of choice in deployment of Electric Power Substations in two scenarios. It is expected that at the end of this work, the criteria evaluated assist in this decision making

Estudo da reação de oxidação de metanol sobre fases intermetálicas ordenadas de AuIn, AuSn e AuSb2 em meio alcalino

The present work assessment materials can be used as fuel cells electrocatalysts. The alkaline fuel cell though was less studied, has some advantages compared to the acid configuration. The materials assesment were Au polycrystalline and intermetallics ordered phases of AuIn, AuSn and AuSb2. Your electrocatalytic properties were studied across cyclic voltametry and chronoamperometry techniques in Sodium Hydroxide 0,15M and Metanol 0,15M solution. The results obtained show a more efficiency to intermetallic AuIn as electrocatalyst for the oxidation reaction of methanol in alkaline medium, it showed high levels of current density and on set potential less positive compared to Au polycrystalline. The intermetallic AuSn showed activity just higher concentrations of methanol. Except AuSb2, who represented himself unstable in alkaline media, the intermetallics AuIn and AuSn present a promising future as anode materials for the oxidation in alkaline medium