SHORT CIRCUIT CALCULATION

In this work, we have designed a voltage regulator circuit for short circuit protection and to enhance the load current rating of the circuit. The Pspice platform is deployed to perform the simulation and the evaluation is done to study the design aspects of the circuit. From the analysis of the proposed regulator circuit, it is observed that as the value of load resistance is increases gradually the regulator output gives more constant voltage

Resumo O objetivo deste artigo é estabelecer um comparativo entre os níveis de curto circuito em média e baixa tensão, calculados em diferentes cenários de contribuição da concessionária e variações nos comprimentos dos cabos de alimentação. Palavras Chave: Cálculo de Curto Circuito, Estudo de Seletividade Introdução Cálculos de curto circuito e estudos de seletividade são atividades fundamentais dentro de um projeto elétrico industrial, sobretudo nos dias de hoje, em que, cada vez mais, os sistemas de produção são bastante dependentes de fontes confiáveis de energia elétrica. Uma parte importante dos cálculos de curto circuito está relacionada ao tratamento matemático que se dá aos cabos de alimentação, sejam eles em média ou baixa tensão. Na prática, é comum se desprezar pequenos lances de cabos (ou apenas trabalhar com comprimentos estimados), por acreditar-se que os mesmos não tem significativa influência nos cálculos. Por outro lado, há quem defenda a máxima precisão em todos e qualquer comprimento de cabo, situação esta, que em determinados casos, pode trazer desnecessárias dificuldades para os cálculos e levantamentos em campo, sem que isto represente incremento qualitativo nos estudos. Neste artigo, apresentaremos na seção 1, uma breve discussão teórica sobre o cálculo de curto circuito. Na seção 2 será abordada a metodologia simplificada para cálculos de curtos circuitos trifásicos. A seção 3 apresenta dois exemplos de cálculo para pontos distintos de um sistema teórico, com alimentação em 13.800V e painéis de baixa tensão alimentados através de transformadores. A seção 4 aborda a influência do comprimento dos cabos do sistema nos níveis de curto circuito onde serão apresentados os resultados de simulações feitas com a utilização do software PTW versão 6.5.2.7, módulo Dapper, variando-se o nível de curto-circuito na entrada do consumidor, o comprimento dos cabos de alimentação geral, o comprimento dos cabos de alimentação dos transformadores e o comprimento dos cabos de alimentação dos painéis gerais de baixa tensão do sistema. Finalmente, na seção 5, destacam-se as principais conclusões deste trabalho.

Input Data: System Voltage: 132 KV Diameter of tube: 0.0635 m Conductor wall thickness: 0.0127 m Ambient Temperature: 35° C = 308.15° K Final operating temperature: 80° C = 353° K Temperature difference between conductor surface & ambient air ∆T= 45° C. Emissivity/Absorption factor () = 0.5 Cross-section area: =-= 3.1416 ⨯ 0.03175-3.1416 ⨯ 0.0254 Derated current for allowable conductor temperature rise I = Where, I = The current through the bus conductor R = DC resistance at the operating temperature Ω/m F = Skin effect coefficient. = Solar heat gain = Convective heat loss = Radiant heat loss = Conductive heat loss

Trabalho elaborado para subsidiar cursos de aterramentos destinado a engenheiros e estudantes de engenharia elétrica. Conteúdo: uma introdução às componentes simétricas é apresentada, em seguida, é mostrada a aplicação desse assunto ao cálculo de curto-circuito de instalações industriais e sistemas elétricos de potência. O trabalho é concluído com um método de obtenção das impedâncias de sequências de linhas de distribuição e de transmissão (baseado nas equações modificadas de Carson e método proposto pelo IEEE).

An electrical power system consists of generators, transformers, transmission and distribution lines. Short circuit and other abnormal conditions often occur on a power system. The heavy current associated with short circuits is likely to cause damage to the equipment if suitable protective relays and circuit breakers are not provided for the protection of each section of the power system. A protective system includes circuit breakers, transducers (CTs and VTs), and protective relays to isolate the faulty section of the power system from the healthy sections. The function of a protective relay is to detect and locate a fault and issue a command to the circuit breaker to disconnect the faulty element. The conventional protective relays are either of electromechanical or static type. The electromechanical relays suffer from several drawbacks such as high burden on instrument transformer, high operating time, contact problem etc. The static relays also suffer from a number of disadvantages such as inflexibility, inadaptability to changing system conditions and complexity. The functions of electromechanical protection systems are now being replaced by microprocessor-based digital protective relays, sometimes called "numeric relays". The increased growth of power system both in size and complexity has brought about the need for fast and reliable relays to protect major equipment and to maintain system stability. The concept of digital protection employing computers which shows much promise in providing improved performance has evolved during the past two decades. Digital computer can easily fulfil the protection requirements of modern power system without difficulties. With the development of economical, powerful and sophisticated microprocessor, there is a growing interest in developing microprocessor-based protective relays which are more flexible because of being programmable and are superior to conventional relays. The objective of this paper is to give a comparative review of microprocessor-based protective relays.

The manuscript presents advanced coupled analysis: Maxwell 3D, Transient Thermal and Fluent CFD, at the time of a rated current occurring on the main busbars in the low-voltage switchgear. The simulations were procured in order to aid the design process of such enclosures. The analysis presented the rated current flow in the switchgear busbars, which allowed determining their temperature values. The main assumption of the simulation was measurements of temperature rise during rated current conditions. Simulating such conditions is a valuable asset in order to design better solutions for energy distribution gear. The simulation model was a precise representation of the actual prototype of the switchgear. Simulations results were validated by experimental research. The heat dissipation in busbars and switchgear housing through air convection was presented. The temperature distribution for the insulators in the rail bridge made of fireproof material was considered: halogen-free polyest...

Concepts on how to calculate electrodynamic forces and stresses which occur during short circuits are a must in the design of switchgear, busbar systems in local equipment and in complete substations arrangements. The results of the studies to determine forces and their consequences are used to design structures, size of the busbar conductors, number of insulators and supports, etc.… This paper shows details about this

Perhitungan dan analisa yang mendalam perlu dilakukan untuk mengetahui kemungkinan besarnya arus hubungan singkat yang dapat timbul pada sebuah sistim distribusi sehingga dapat dilakukan pencegahan melalui pengaturan setting pada alat proteksi arus lebih dan juga pemilihan peralatan atau komponen listrik yang akan digunakan dengan menyesuaikan rating ketahanannya terhadap arus hubugnan singkat disesuaikan dengan hasil analisa dan perhitungan Arus Hubungan Singkat.

MANSUR, Danilo. Métodos de cálculo da capacidade de curto-circuito em sistemas elétricos
de potência. Graduação em Engenharia Elétrica – Faculdade de Engenharia, Universidade do
Estado do Rio de Janeiro, Rio de Janeiro, 2019.

A capacidade de curto-circuito é uma grandeza que representa a máxima corrente de
falta que uma barra de um sistema elétrico de potência produz no ponto de falta, estando
associada a força desse barramento. Em função da grande variação e complexidade da
topologia dos sistemas elétricos, condições de carga e geração e ampliação da geração
distribuída, a capacidade de curto-circuito nas diversas barras do sistema pode variar
expressivamente. Consequentemente, é inviável aplicar correntes de curto-circuito em todas
as barras de um sistema para determinação deste parâmetro, de forma que algumas
metodologias devem ser empregadas para auxílio destes cálculos. Métodos algébricos e
computacionais como o método PU e MVA equivalente e experimentais, com auxílio de
eletrônica de potência, tem sido amplamente estudados frente a importância deste parâmento
para o planejamento e proteção dos sistemas elétricos de potência.

Palavras-chave: Curto-Circuito. Energia. Proteção.

Current and force calculations in different short-circuit conditions are required for short-circuit performance analysis of a multi-winding traction transformer which is one of the most important requirements in its design process. This paper extends the available low-frequency three-winding star equivalent circuits to develop a novel equivalent circuit for the four-winding traction transformers. The leakage inductances of the traction transformer are determined and employed to calculate the parameters of this developed star model. It is shown that the star equivalent circuit is a valid and appropriate model to simulate the steady-state and dynamic performance of the traction transformer under different short-circuit conditions. To analyze the short-circuit performance of the transformer, the short-circuit currents (simulated by the introduced model) are employed to compute the electromagnetic forces for a typical dry-type traction transformer. The analytical and numerical methods are used for short-circuit force calculations, and those results are compared against each other.

Doubly Fed Induction Generators DFIG are nowadays widely used in variable speed wind power plants. The dynamic interaction between variable speed DFIG wind turbines and the power system which is subjected to disturbances, such as short circuit faults, is an important issue. The ability of the wind power plant to stay connected to the grid during disturbances is important to avoid a cascading effect due to lack of power. This paper investigates the impact of fault ride through on the stability of DFIG wind turbine using crowbar resistance. Simulation test using MATLAB-Simulink toolbox is implemented on a 9 MW wind farm exports its power to 120 KV grid. The simulation is performed using different crowbar resistances. The variations of rotor current, rotor speed, DC-link voltage, active power and reactive power of the wind farm are investigated. Arabia. His fields of interest are digital protection of power systems, power system stability, and renewable energy systems.

Los participantes en este entrenamiento disfrutarán de una experiencia de aprendizaje única, en la cual se presenta una introducción exhaustiva e integral de las funciones básicas de software DIgSILENT PowerFactory.

El participante de este entrenamiento obtendrá una visión  completa de las principales funcionalidades del programa de DIgSILENT PowerFactory.

This paper proposes a terminal crowbar protection technique for Doubly Fed Induction Generators (DFIG) to protect the rotor converter and enhance network stability during grid disturbances. Simulation test using MATLAB-Simulink toolbox is implemented on a 9 MW wind farm exports its power to 120 KV grid. The simulation is performed using different values of crowbar resistances. The variations of rotor current, rotor speed, DC-link voltage, active power and reactive power of the wind farm are investigated. Also, a comparison between the conventional crowbar and the proposed crowbar protection techniques is investigated. Arabia. His fields of interest are digital protection of power systems, power system stability, and renewable energy systems.

Purpose-This paper presents the theory for computing the positive and zero sequence admittance matrices of three-phase four-winding transformers and autotransformers. These matrices are required in load-flow and short-circuit calculations. Methodology-The positive and zero sequence impedances between windings, which are available from standard transformer test reports, are modeled as mutual impedances between each pair of windings. These mutual impedances are used to build a 4x4 impedance matrix taking into account the winding voltage ratios. Also a 4x4 matrix of voltage and current relationship is built. Using these two matrices, the positive sequence admittance matrix of a transformer or autotransformer is computed. For zero sequence admittance matrices, the connection group and grounding impedance of each winding is also taken into account. Research implications-This theory can be useful to upgrade load-flow and short-circuit software to handle four-winding transformers and autotransformers, in a reliable and straightforward manner.

Copper and aluminium are the two conductors most commonly used in transformer windings. This study presents a comprehensive comparison of distribution transformers built either with copper or with aluminium windings. The comparison is based on winding material conductivity, density, cost, connectivity, oxidation, machinability and behaviour under short-circuit. Additionally, a parametric analysis of transformer designs as a function of the cost of copper against aluminium is presented. The study establishes the winding material cost range that indicates when it is more economical to build the transformer windings with copper or with aluminium. All comparisons are carried out with cost of optimised transformer designs that fulfil all specifications together with manufacturing and operating constraints.

Renewable Energy Sources are one of the greatest challenges for the future of Electrical Production and Distribution. There are two main renewable sources that are subjected to the development of Electrical Production; Wind and Sun. Wind Energy as the most targeted source for Europe from the year 2018, offers countless challenges of studying, developing and projecting of Wind Farms. Reports and studies quote that the European Wind Energy will exceed 250 GW capacity by 2022.
One of the most important aspects of wind power plant (WPP) is to determine safety and reliability of production and distribution. Evaluating different type of faults and fault contribution of wind turbines are a determinant factor when talking about safety.

Resumo: Para obter uma boa soldabilidade dos aços inoxidáveis ferríticos, na maioria das vezes, as empresas recorrem ao arames inoxidáveis austenítico em função de sua boa resistência mecânica, tenacidade e ductilidade. Arames de aço inoxidável ferrítico estabilizados ao nióbio e titânio estão sendo desenvolvidos para obter boa qualidade e baixo custo. O objetivo deste trabalho é estudar a influência da composição do gás de proteção (argônio puro e misturas com oxigênio ou dióxido de carbono) na composição química e microestrutura do cordão de solda do processo GMAW com transferência por curto-circuito. Foram utilizados dois arames eletrodos estabilizados (ER430Ti e ER430LNb) e um arame eletrodo não estabilizado (ER430) e como metal de base o aço inoxidável ferrítico UNS 43932. Os resultados mostraram que o aumento do dióxido de carbono no gás de proteção aumenta o teor de carbono no cordão de solda, tendo como conseqüência para o arame não estabilizado um aumento significativo da quantidade de martensita no cordão de solda, caso não observado de forma significativa com o aumento do oxigênio. Para o arame ER430LNb não verificou a presença da martensita de contorno de grão. O aumento tanto do dióxido de carbono como do oxigênio diminuiu os teores de Mn e Si para os arames ER430LNb e ER430, caso não verificado no arame ER430Ti.

The manuscript presents advanced coupled analysis: Maxwell 3D, Transient Thermal and Fluent CFD, at the time of a rated current occurring on the main busbars in the low-voltage switchgear. The simulations were procured in order to aid the design process of such enclosures. The analysis presented the rated current flow in the switchgear busbars, which allowed determining their temperature values. The main assumption of the simulation was measurements of temperature rise during rated current conditions. Simulating such conditions is a valuable asset in order to design better solutions for energy distribution gear. The simulation model was a precise representation of the actual prototype of the switchgear. Simulations results were validated by experimental research. The heat dissipation in busbars and switchgear housing through air convection was presented. The temperature distribution for the insulators in the rail bridge made of fireproof material was considered: halogen-free polyest...

In this work, we have designed a voltage regulator circuit for short circuit protection and to enhance the load current rating of the circuit. The Pspice platform is deployed to perform the simulation and the evaluation is done to study the design aspects of the circuit. From the analysis of the proposed regulator circuit, it is observed that as the value of load resistance is increases gradually the regulator output gives more constant voltage.

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This paper deals with the transient performance of a self excited induction generator in a wind power plant under different fault conditions. An induction generator and grid equipment may be damaged when a sudden disturbance occurs, for example, a sudden disconnection from the utility grid. The reasons for this are overvoltage and over speed. This paper also made an analysis when there is sudden disconnection of self excitation capacitance .This paper analyzes this phenomena using MATLAB/SIMULINK and coincides with its corresponding mathematical equation. Response of the system to disturbances reveals its excellent transient performance. The system has a good overload capability and is free from operational problems related with short circuit and loss of excitation.

Copper and aluminium are the two conductors most commonly used in transformer windings. This study presents a comprehensive comparison of distribution transformers built either with copper or with aluminium windings. The comparison is based on winding material conductivity, density, cost, connectivity, oxidation, machinability and behaviour under short-circuit. Additionally, a parametric analysis of transformer designs as a function of the cost of copper against aluminium is presented. The study establishes the winding material cost range that indicates when it is more economical to build the transformer windings with copper or with aluminium. All comparisons are carried out with cost of optimised transformer designs that fulfil all specifications together with manufacturing and operating constraints.

Input Data: System Voltage: 132 KV Diameter of tube: 0.0635 m Conductor wall thickness: 0.0127 m Ambient Temperature: 35° C = 308.15° K Final operating temperature: 80° C = 353° K Temperature difference between conductor surface & ambient air ∆T= 45° C. Emissivity/Absorption factor () = 0.5 Cross-section area: =-= 3.1416 ⨯ 0.03175-3.1416 ⨯ 0.0254 Derated current for allowable conductor temperature rise I = Where, I = The current through the bus conductor R = DC resistance at the operating temperature Ω/m F = Skin effect coefficient. = Solar heat gain = Convective heat loss = Radiant heat loss = Conductive heat loss

Voltage source converters (VSCs) are self-commutated converters able to generate AC voltages with or without the support of an AC connecting grid. VSCs allow fast control of active and reactive powers in an independent way. VSCs also have black start capability. Their use in high-voltage direct current (HVDC) systems, comparative to the more mature current source converter (CSC)-based HVDC, offers faster active power flow control. In addition, VSCs provide flexible reactive power control, independent at each converter terminal. It is also useful when connecting DC sources to weak AC grids. Steady-state RMS analysis techniques are commonly used for early-stage analysis, for design purposes and for relaying. Sources interfaced through DC/AC or AC/DC/AC converters, opposite to conventional generators, are not well represented by electromotive forces (E) behind impedance models. A methodology to include voltage source converters (VSCs) in conventional RMS short-circuit analysis techniques is advanced in this work. It represents an iterative procedure inside general calculation techniques and can even be used by those with only basic power electronics knowledge. Results are compared to those of the commercial software package PSS®CAPE to demonstrate the validity of the proposed rmsVSC algorithm.