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Recently the issues of reactive power compensation and voltage control have become important in the operation of power systems, due to the constant growth of world demand as well as diversification of the connected load. Several solutions have been developed to provide greater flexibility to power systems during light load and maximum demand condition. These are two of the most critical conditions...
A formulation based on 2D Cartesian and axisymmetric finite-element (FE) models, modified nodal analysis (MNA) and a multi-field system approach is proposed to analyze a three-phase power transformer. Interesting capabilities are thus achieved, overcoming the difficulties naturally arising with 3D simulations: high computational times and memory demand. A 2D Cartesian FE model is employed to represent...
This paper presents the electromagnetic transient analysis of a Permanent Magnet Synchronous Generator (PMSG) using the finite element method in two dimensions. A study case is modeled where the generator is connected to a three-phase load through an electronic converters. The PMSG was modeled in the finite element software Flux 2D and the control of the passive elements of the converters was modeled...
The aim of this paper is to assess the performance of several multi-objective optimization techniques using a modified version of the edge window decoding technique, used in telecommunication networks, but adapted for representing power distribution systems during reconfiguration. Thus, the encoding scheme together with efficient genetic operators were embedded in several optimization techniques analyzed,...
In the analysis of field problems, cases with open boundaries often arise. The finite element method, frequently used for the numerical solution of field problems, is naturally adequate for closed boundary problems; however, the definition of infinite elements can overcome such limitation. In this paper, mapped infinite elements are used to solve open boundary field problems defined in terms of a...
This paper presents an analysis of the thermal behavior (convection, conduction and radiation) in steady state of a dry-type distribution power transformer. Dry-type transformers are mainly used in applications where the risk of fire and environmental policy does not allow the use of oil-filled transformers. The model takes into account the fluid (air) and solves the heat transfer equation for non-isothermal...
The virtual air-gap variable reactor is a recently proposed device whose inductive reactance may be continuously varied over a wide range. The performance of this variable reactor is analysed with the help of magnetic field numerical computations. Key constructional features are related to the effects they produce in the magnetic characteristics of the device, from where design guidelines are identified...
Fixed or variable reactors are required in modern high voltage transmission systems. The virtual air-gap principle offers an alternative avenue for the development of controllable compensation devices to overcome voltage regulation problems in high voltage transmission systems. In this paper the scaling of the virtual air-gap principle to high voltage and large power devices is considered. A novel...
This paper describes a genetic algorithm (GA) developed for the reconfiguration of radial distribution systems. The reconfiguration is treated as an optimization problem of combinatory nature, where the aim is to obtain a configuration with minimal power losses, iterations and also with some distribution system restrictions. The initial population of the GA is obtained using spanning trees techniques...
In this work, a computer model for calculating surge distribution in power transformer windings is presented. The model is based on multiconductor transmission line theory, considering each disk coil as the basic element for the analysis. The electric parameters R, L, C and G are calculated by using conventional formulations. The electrical parameters are used for calculating modal parameters in order...
Series compensation of long transmission lines is widely used in electrical power systems in order to reduce losses and increase the transmission line capacity. However, for certain values of compensation, the series connected capacitors interact with the mechanical elements of the turbine-generator group leading to sub-synchronous resonance, which could damage or destroy the generation unit. Due...
In this work a computer model for calculating surge distribution in transformer windings is presented. The transformer model is developed using transmission line theory. The capacitance, inductance, resistance and conductance are calculated with simple formulations. The electrical parameters are used for calculating modal parameters in order to represent the winding as a two port network. The model...
In this paper, finite element (FE) field models for the calculation of resistance, inductance and capacitance in high voltage machine windings are developed. The models take into account frequency-dependent phenomena such as the skin and proximity effects and the magnetic flux penetration into the iron core. The accuracy of the electrical parameters calculated with the field models was verified by...
Time domain terminal models for high voltage induction motor windings are developed for simulating transient overvoltages due to switching operations in industrial installations. The models are based on the network synthesis of the terminal impedance for short circuit and open circuit conditions of the winding. The process of synthesis is carried out taking into account the minimum and maximum resonant...
Summary form only given. This work presents a numerical analysis of losses generated in the tank wall surrounding the high-current bushings of pad-mounted transformers using a three-dimensional finite-element approach. Two cases are analyzed to study the impact of inserting small plates of different geometry (located near the high-current phases) on the reduction of tank losses. Significant reductions...
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