An estimated 30% of the faults in Induction Machine (IM) are related to its stator. These faults are mostly in the form of an Inter-Turn Short Circuit (ITSC) fault i.e., when two winding inside the stator of IM are shorted due to insulation failure. However, ITSC fault can be avoided by detecting them in advance and then scheduling the maintenance of the IM. This thesis studies two methods for detecting this incipient ITSC fault in a three-phase IM and then estimating the stator resistance unbalance due to the ITSC fault. The first method is based on the asymmetry caused in the IM by the ITSC fault. As a result of this asymmetry, the negative sequence components of the stator voltages and the stator currents are generated inside the IM. A healthy IM also have these negative sequence components due to the manufacturing process and the supply voltage unbalances. The characteristics and the compensation methods of these negative sequence components in a healthy IM are discussed. The results show that after compensating the negative sequence components in a healthy machine, they can be used for detecting an ITSC fault and then to calculate the fault quantities as well as the stator resistance unbalances. The second method for detecting an ITSC fault is based on analysing the stator resistance unbalances. A three-phase drive is used to inject DC voltage in the stationary reference frame. The DC current generated by this DC voltage is measured and then by applying Ohm’s law stator phase resistances are calculated. In a healthy IM, the phase resistances are balanced. However, in case of ITSC fault in any of the phases, the phase resistance of that phase deviates from those of the other two phases which can be utilized for detecting ITSC fault. / Uppskattningsvis 30% av alla fel i induktionsmaskiner (IM) är kopplad till dess stator. Dessa fel är i huvudsak Inter-Turn Short Circuit (ITSC)-fel, dvs. två lindningar inom IM:ens stator blir kortsluta pga. ett isoleringsfel. Emellertid kan man undvika ITSC-fel genom att detektera dem i förhand och planera underhåll. Det här examensarbetet undersöker två metoder för att detektera ett förestående ITSC-fel i en tre-fas IM. Den första metoden är baserad på asymmetrin i IM:er pga. ITSC-felet. Resultatet av den här asymmetrin är att en negativ sekvens genereras i IM:ens statorspänning och statorström. En oskadad IM kan också visa dessa negativa sekvenser pga. tillverksprocessen och statorspänningsobalanser. Egenskaperna och kompensationsmetoderna för dessa negativa sekvenser i en oskadad IM kommer att diskuteras. Resultaten visar att efter kompenseringen av de negativa sekvenserna i en oskadad IM, kan de användas för att detektera ITSC-fel och efteråt för att beräkna felstorheter och även statormotståndobalanser. Den andra metoden för att detektera ITSC-fel är baserad på en undersökning av statormotståndobalanser. Ett tre-fas-drivsystem används för att injektera likspänning i den stationära referensramen. Likströmmen som följer av denna likspänning mäts och statorfasmotstånden beräkna efteråt med Ohms lag. I en oskadad IM är fasmotstånden balanserade. Däremot, när ett ITSC-fel uppstår i en fas, avviker fasmotståndet i den felaktiga fasen från de andra två fasernas, vilket kan användas för att detektera ITSC-fel.

Die Physikalisch-Technische Bundesanstalt (PTB) unterstützt vielfältig die Gesellschaft, Wirtschaft und Wissenschaft. Eine ihrer Kernkompetenzen als das nationale Metrologie-Institut der Bundesrepublik Deutschland ist die Messtechnik. In diesem Sinne kalibriert die Arbeitsgruppe „Solarzellen“ der PTB i. d. R. den Kurzschlussstrom unter Standardtestbedingungen (I_STC) von Referenzsolarzellen. Der I_STC von Referenzsolarzellen ist in Photovoltaik-Kalibrierketten bei der Bestimmung der Bestrahlungsstärke von zentraler Bedeutung und fließt signifikant in die Berechnung der Wirkungsgrad von Solarzellen und Solarmodulen ein. Um den I_STC einer Solarzelle mit geringster Messunsicherheit zu bestimmen, wurde die Differential Spectral Responsivity (DSR)-Methode verwendet. Sie basiert auf der Messung der differentiellen spektralen Empfindlichkeit bei unterschiedlichen Bestrahlungsstärken. Anhand dieser kann die absolute spektrale Empfindlichkeit s(λ) unter Standardtestbedingungen sowie der I_STC berechnet werden. Da jedoch die Umgebungsbedingungen meistens von den STC abweichen, reichen letztere nicht zum umfassenden Vergleich der Wirkungsgrade in der Praxis aus. Um Einflussfaktoren (Temperatur, Bestrahlungsstärke, Winkelabhängigkeit,...) genauer untersuchen zu können, wurde im Rahmen dieser Arbeit an der PTB ein neuer Laser-basierter DSR-Messplatz aufgebaut und charakterisiert. Mit dem neuen Messplatz wurden c-Si Referenzsolarzellen, organische Solarzellen auf Basis kleiner Moleküle sowie Farbstoffsolarzellen umfassend untersucht. Unter anderem wurden die elektrischen Leistungsparameter einer organischen Solarzelle (aktive Schicht: DCV5T-Me:C60) mit denen einer c-Si Solarzelle verglichen. Es zeigt sich, dass der Wirkungsgrad der organischen Solarzelle mit zunehmender Bestrahlungsstärke sinkt und mit zunehmender Temperatur steigt, während die c-Si Solarzelle ein gegensätzliches Verhalten aufweist. Darüber hinaus wurde u.a. die Winkelabhängigkeit der zweiten organischen Solarzelle (aktive Schicht: C60:DCV5T-Me(3,3)) untersucht und mit den Resultaten einer c-Si Solarzelle verglichen. Diese Untersuchungen haben ergeben, dass die Winkelabhängigkeit des Kurzschlussstroms der organischen Solarzelle im Vergleich zu einer c-Si Solarzelle insbesondere zwischen 20° < ϑ < 60° eine „Super-Kosinus-Anpassung“ aufweist. Ergänzend wurde an der PTB im Rahmen dieser Arbeit ein mobiler Messplatz für Outdoormessungen aufgebaut. Mit diesem konnten die mittels Indoor-Untersuchungen erhaltenen spektralen Empfindlichkeiten mit Outdoor-Messungen verglichen werden. Des Weiteren wurden spektrale Charakterisierungen der Himmelshalbkugel durchgeführt und Methoden für Korrekturen von Sekundärkalibrierungen untersucht.

Au sein d'un convertisseur la défaillance d'un composant de puissance est un événement critique tant par le risque d'explosion du boitier et sa propagation au sein du système (forte énergie stockée dans l'alimentation) que par l'interruption de service qui en découle (systèmes embarqués, systèmes de production en flux tendu). Ce mémoire de thèse propose un ensemble de solutions nouvelles portant sur la problématique de l'isolement ultime de défauts "derniers secours" d'une part, et sur la connexion "automatique" et à faible "coût" d'un circuit en secours. L'objectif de cette approche globale est de concilier "sécurité électrique absolue" et "continuité de service" pour les systèmes de conversion sensibles devant être intégrés au coeur des applications critiques. Le premier chapitre et son annexe permettent de rappeler les causes et les conséquences des défauts internes au sein d'une structure de base d'onduleur à deux niveaux de tension, laquelle fait l'objet de nombreuses simulations de modes dégradés en configuration variateur de vitesse sur machine synchrone. De cette analyse il ressort qu'une structure d'isolement symétrique à deux voies couplées, placées sur les pôles du bus DC, à déclenchement spontané (fusible) et/ou commande (rupteur), est à même de sécuriser toutes les mailles du circuit, de façon modulaire et non intrusive. / In all these traditional industries, or in more sensitive sectors and high technology, it appears that the safe operation of power systems becomes a critical and strategic area essential. In the area of application that focuses, design dependability and now rests primarily on an approach to reliability of components used, the use of close protection, monitoring alarms and management stop / reset / recovery. In our view, this approach is incomplete quickly when electrical safety and absolute continuity of a permanent mission should be carried out simultaneously in the presence of an internal failure of sensitive functions for low and medium power (eg, orders and bodies actuation of vehicles) or highly critical (nuclear). In this area, topologies and failure modes are at the heart of the problem. In this paper, we will focus primarily on the inverters and choppers structures at two levels of voltage (single-cell arm, <1kV), with simple configuration and multiphase parallel, although the concepts are presented, as examples, partially extrapolated to the structures of three voltage levels (arms multicellular) and rectifier (low-frequency phase control and high-frequency switching PWM). We will highlight the need to limit the intensity of these failures and to electrically isolate the defective cell and symmetrically of this inverter by multipole devices, passive or spontaneous breaking mixed cut ordered in the form of fuses integrated and distributed of multi-channel passive isolators, to imagine and develop. We will show that this process of isolation of the last backup is needed to connect, form series or parallel to the defective cell, a cell rescue in passive redundancy. The cell structure backup connection pooled by spontaneous (automatic) is especially promising as detailed in our eyes because of its simplicity and its integrability. Next, we present the isolation technologies fuse (not included, miniatures, CMS and multilayer chip fuse), their characteristics, their current limitations and operating in a switching cell test. A methodology and design of symmetrical two-way fuse (dual-fuse) on FR4 PCB - Copper will be presented in Comsol ™ and evaluated initially in static thermal IR. A passive two-way switch, relatively original material for integrating energy embedded in FR4 substrate, will be presented and fully dimensioned plans on electrical, thermal and mechanical also using finite element simulations in Comsol ™. Another aspect of exploratory analysis, mainly experimental, or to characterize the failure modes of bullets and casings ultimate power compared between the technologies of encapsulation by epoxy resin (standard discrete case) and a silicone gel (module) is provided under conditions of stress controlled and reproducible. This step is necessary to characterize the resistive mode of a chip based on faulty stresses and stability over time of the residual strength according to the nature of the encapsulant, ie the very sustainability of this failure mode. A mixed-encapsulant resin - gel will be presented and characterized, providing an excellent compromise for medium power applications. Positive results and little known today, will allow us to exploit in the next chapter, this property of stable ohmic mode of the chip failed in a structure to aid automated connection series interesting. In the end, we will detail the demonstrator prototype and introduced to the context with which we will validate the isolation structures and prototypes fuses the property of stable ohmic mode highlighted in the aspect of technological analysis of selected devices. These results allow us to refine the solutions adopted for specifications and guide future management strategy of defects whether internal or external to the topology. Supervisor digital device - sensor for the detection and reconfiguration of internal control orders will be assessed.

The report is a study of error management and localization in underground cable network with very little overhead line. Error management is treated with the theoretical troubleshooting model and theoretical model with practical feedback. The work relates to the fact that troubleshooting has been complicated when the supply safety in the electricity grid increases. Difficult troubleshooting is followed by a difficult reset work in case of malfunctioning in the network and it leads to longer interruptions.The grid is built with main feed and radial feeds. In the cable stretches, an interval of the short-circuit current occurs with a minimum and a maximum current below the distance. Depending on how the network is built, multiples of same error current is created, that create harder error-handling. The analysis examines which locations in the grid, which help increase the number of alternative malfunctions and if there is any alternative method to solve the problem. The report deals with the connection between currents in main feed and in radial feeds along the line. There appears to be a connection between the emergences of currents with similar current values in several places. A network consisting of a main feed and a plurality of radial feeds, the occurrence of streams in several places is a disadvantage in the troubleshooting task and the work is adversely affected and the troubleshooting work becomes more difficult. / Rapporten är en studie om felhantering och fellokalisering i ett markbelagt kabelnät med en väldigt liten del friledning. Felhanteringen be-handlas med både dataprogramvara och teoretiska beräkningar. Arbetet relaterar till att felsökningen försvåras när leveranssäkerheten i elnätet ökar. Svårare felsökning är följt av ett försvårat återställningsar-bete vid fel i nätet som leder till längre avbrottstider. Elnätsområdet är uppbyggt med huvudmatning samt radiella matning-ar. I kabelsträckorna uppkommer ett intervall på kortslutningsström-men med en minsta och en högsta ström under sträckan. Beroende på hur nätet är uppbyggt skapas multiplar av felställen som skapar svårare felhantering. Analysen undersöker vilka ställen i elnätet som bidrar till att antalet alternativa felställen ökar och om det finns någon alternativ metod att lösa problemet. Rapporten behandlar sammanbandet mellan strömmar i huvudmatning och i radiella matningar längs ledningens sträcka. Det visar sig vara ett samband mellan uppkomsten av strömmar med liknande strömvärden på ett flertal ställen. Ett nät som består av en huvudmatning och ett flertal radiella matningar är uppkomsten av samma kortslutningsströmmar på flera ställen. Det är en nackdel i felsökningsarbetet och arbetet påverkas negativt och fel-sökningsarbetet blir svårare.

Este trabalho apresenta uma metodologia computacional para coordenação automática de dispositivos de proteção contra sobrecorrente em sistemas elétricos industriais radiais, tendo como principais vantagens a exatidão nos cálculos dos ajustes e a proposição automática de soluções para eventuais problemas de coordenação, sempre que possível. A metodologia é utilizada tanto para proteção individual contra sobrecorrente dos equipamentos quanto para coordenação dos dispositivos de proteção do sistema. É feito um estudo detalhado dos requisitos de proteção de sobrecorrente dos equipamentos empregados em sistemas elétricos industriais, como motor, cabo e transformador, bem como dos dispositivos mais utilizados, fusível e disjuntor de baixa tensão, com ênfase para a proteção por meio de relés digitais de sobrecorrente. O método é usado para o desenvolvimento de uma ferramenta computacional. Há uma exposição dos algoritmos utilizados para busca e cálculo dos ajustes dos dispositivos de cada equipamento. Por fim é realizado um teste da ferramenta com dois exemplos de sistemas elétricos industriais, mostrando que o mesmo apresenta bom desempenho quanto à exatidão no cálculo dos ajustes e na redução do tempo despendido em estudos de coordenação da proteção e seletividade. / This work presents a computational methodology for automatic overcurrent coordination of protection devices in radial industrial electrical systems, which main advantages are the accuracy in the devices\' settings calculation and the automatic proposition of solutions to coordination problems, whenever it is possible. The methodology is used both for equipment individual overcurrent protection and for protection devices coordination. A detailed study of the overcurrent protection requirements of the equipments used in industrial electrical systems, such as motor, cable and transformer is carried out, as well as of the most used protection devices, fuses and low voltage circuit breaker, with emphasis on the protection by means of overcurrent digital relays. The method is used to develop a computational tool. There is an explanation of the search and settings calculation algorithms applied to the devices of each equipment. Finally, two examples of industrial electrical systems are used to assess the performance of the proposed methodology. It is shown that it presents good performance on the accuracy in the calculation of the devices settings and on amount of time spent on protection coordination and selectivity studies.

Esta dissertação tem por propósito analisar os impactos da geração distribuída sobre as correntes de curto-circuito e sobre a proteção das redes de média tensão das concessionárias de distribuição de energia elétrica usando uma abordagem paramétrica. A principal motivação deste trabalho são os recentes incentivos regulatórios que estão fomentando a geração distribuída no Brasil. Contudo, as redes de distribuição convencionais foram projetadas para serem passivas e a introdução da geração poderá causar problemas de ordem técnica que ainda precisam ser resolvidos. Tais problemas foram pesquisados e aqueles relacionados com os impactos sobre as correntes de curto-circuito foram enfatizados. As normas técnicas das concessionárias também foram investigadas porque seus requisitos, como a ligação dos transformadores de acoplamento, influem nas correntes de curto-circuito. Para se calcular as correntes de curto-circuito, desenvolveu-se uma planilha eletrônica cujos resultados foram validados com programas comerciais de análise de redes elétricas. Esta ferramenta foi utilizada para demonstrar, através de exemplos, o impacto causado pela geração distribuída sobre as correntes de curto-circuito e, posteriormente, para realizar as análises paramétricas nas quais a influência de cada variável foi avaliada. A aplicação do método paramétrico permitiu o estudo de possíveis limites para a potência de um gerador distribuído em função dos impactos admissíveis, de seu ponto de conexão, de seus parâmetros elétricos e dos parâmetros elétricos da rede. / The purpose of this thesis is to analyse the impacts of distributed generation on short-circuit currents and protection of the distribution utilities medium voltage networks using a parametric approach. The new regulations that are promoting the distributed generation in Brazil are the main motivation for this work. However, the conventional distribution networks were designed to be passive; therefore the integration of generation may cause some technical problems yet to be solved. Such problems were researched and those related to the impacts on short-circuit currents were emphasized. The utilities technical standards were also explored as their requirements affect the short-circuit currents (e.g. the transformers connections). A spreadsheet was developed in order to calculated the short-circuit currents and it was validated comparing its results to those of a commercial network analysis software. This tool was used to expose the impacts of distributed generation on short-circuit currents through examples and also to carry out parametric analysis in which the influence of every variable was evaluated. The application of a parametric method made it possible to define the maximum installed capacity of a distributed generator as a function of the allowed limits to the impacts on the short-circuit currents, its point of coupling, its electrical parameters and the electrical parameters of the network.

A transmissão de energia em corrente contínua, a partir de conversores fonte de tensão, é oportuna ao progresso do sistema elétrico de potência e tem permitido vantajosas aplicações. Muito se dá, devido ao emprego na conexão de sistemas com frequências distintas, além da redução de perdas na transmissão, provida pelas características operacionais destes. VSCs também promovem o controle do fluxo de potência, possibilitando uma efetiva contextualização no âmbito das redes inteligentes. Diante deste cenário, este estudo pretende construir um perfil de corrente através do Cálculo de Curto-Circuito Probabilístico, que emprega a Simulação de Monte Carlo, para prover as informações ao desenvolvimento de projetos de equipamentos, ajustes da proteção e controle de sistemas de transmissão em corrente contínua. A Simulação de Monte Carlo requer muitas iterações, tendo um custo computacional elevado. Se forem executadas em programas comerciais, exige um tempo elevado para leitura dos sinais em arquivos. Devido a isso, um programa de código livre usando linguagem C++, foi desenvolvido para possibilitar acesso aos sinais de interesse ainda em memória, reduzindo desta forma o tempo computacional. Além disso, para melhorar a performance, foram usadas técnicas de processamento paralelo e de computação em nuvem. Desta forma, este estudo contribui com informações indispensáveis ao projeto de equipamentos de proteção dos sistemas de transmissão em corrente contínua de forma a cooperar com o desenvolvimento consistente desta tecnologia. / Transmitting electrical power in direct current using a VSC is suitable for the progress of these systems and has remarkable and advantageous applications. This happens in order to connect two systems with distinct frequencies. This type of line is also used in the reduction of losses in transmission over long distances, provided by their operating characteristics. These converters also promote the control of power flow between distinct generation units, making them effective in the context of Smart Grids. Based on this, the purpose of this research is to construct a profile of a current using a Probabilistic Short-Circuit Analysis by Monte Carlo Simulation to provide basic data to the optimum development of design equipment in protection and control. The Monte Carlo Simulation requires many iterations to find an optimal result. An open source program using C++ language was developed to describe all the system models variables in order to decrease the computation time, as it is time consuming to read signals stored on a disk using commercial software. Moreover, in order to lower computation costs, parallel process techniques and cloud computing were used. Therefore, this study contributes to the literature by providing essential information for designing equipment for Direct Current transmission protection systems.

A transmissão de energia em corrente contínua, a partir de conversores fonte de tensão, é oportuna ao progresso do sistema elétrico de potência e tem permitido vantajosas aplicações. Muito se dá, devido ao emprego na conexão de sistemas com frequências distintas, além da redução de perdas na transmissão, provida pelas características operacionais destes. VSCs também promovem o controle do fluxo de potência, possibilitando uma efetiva contextualização no âmbito das redes inteligentes. Diante deste cenário, este estudo pretende construir um perfil de corrente através do Cálculo de Curto-Circuito Probabilístico, que emprega a Simulação de Monte Carlo, para prover as informações ao desenvolvimento de projetos de equipamentos, ajustes da proteção e controle de sistemas de transmissão em corrente contínua. A Simulação de Monte Carlo requer muitas iterações, tendo um custo computacional elevado. Se forem executadas em programas comerciais, exige um tempo elevado para leitura dos sinais em arquivos. Devido a isso, um programa de código livre usando linguagem C++, foi desenvolvido para possibilitar acesso aos sinais de interesse ainda em memória, reduzindo desta forma o tempo computacional. Além disso, para melhorar a performance, foram usadas técnicas de processamento paralelo e de computação em nuvem. Desta forma, este estudo contribui com informações indispensáveis ao projeto de equipamentos de proteção dos sistemas de transmissão em corrente contínua de forma a cooperar com o desenvolvimento consistente desta tecnologia. / Transmitting electrical power in direct current using a VSC is suitable for the progress of these systems and has remarkable and advantageous applications. This happens in order to connect two systems with distinct frequencies. This type of line is also used in the reduction of losses in transmission over long distances, provided by their operating characteristics. These converters also promote the control of power flow between distinct generation units, making them effective in the context of Smart Grids. Based on this, the purpose of this research is to construct a profile of a current using a Probabilistic Short-Circuit Analysis by Monte Carlo Simulation to provide basic data to the optimum development of design equipment in protection and control. The Monte Carlo Simulation requires many iterations to find an optimal result. An open source program using C++ language was developed to describe all the system models variables in order to decrease the computation time, as it is time consuming to read signals stored on a disk using commercial software. Moreover, in order to lower computation costs, parallel process techniques and cloud computing were used. Therefore, this study contributes to the literature by providing essential information for designing equipment for Direct Current transmission protection systems.

Este trabalho apresenta uma metodologia computacional para coordenação automática de dispositivos de proteção contra sobrecorrente em sistemas elétricos industriais radiais, tendo como principais vantagens a exatidão nos cálculos dos ajustes e a proposição automática de soluções para eventuais problemas de coordenação, sempre que possível. A metodologia é utilizada tanto para proteção individual contra sobrecorrente dos equipamentos quanto para coordenação dos dispositivos de proteção do sistema. É feito um estudo detalhado dos requisitos de proteção de sobrecorrente dos equipamentos empregados em sistemas elétricos industriais, como motor, cabo e transformador, bem como dos dispositivos mais utilizados, fusível e disjuntor de baixa tensão, com ênfase para a proteção por meio de relés digitais de sobrecorrente. O método é usado para o desenvolvimento de uma ferramenta computacional. Há uma exposição dos algoritmos utilizados para busca e cálculo dos ajustes dos dispositivos de cada equipamento. Por fim é realizado um teste da ferramenta com dois exemplos de sistemas elétricos industriais, mostrando que o mesmo apresenta bom desempenho quanto à exatidão no cálculo dos ajustes e na redução do tempo despendido em estudos de coordenação da proteção e seletividade. / This work presents a computational methodology for automatic overcurrent coordination of protection devices in radial industrial electrical systems, which main advantages are the accuracy in the devices\' settings calculation and the automatic proposition of solutions to coordination problems, whenever it is possible. The methodology is used both for equipment individual overcurrent protection and for protection devices coordination. A detailed study of the overcurrent protection requirements of the equipments used in industrial electrical systems, such as motor, cable and transformer is carried out, as well as of the most used protection devices, fuses and low voltage circuit breaker, with emphasis on the protection by means of overcurrent digital relays. The method is used to develop a computational tool. There is an explanation of the search and settings calculation algorithms applied to the devices of each equipment. Finally, two examples of industrial electrical systems are used to assess the performance of the proposed methodology. It is shown that it presents good performance on the accuracy in the calculation of the devices settings and on amount of time spent on protection coordination and selectivity studies.

Esta dissertação tem por propósito analisar os impactos da geração distribuída sobre as correntes de curto-circuito e sobre a proteção das redes de média tensão das concessionárias de distribuição de energia elétrica usando uma abordagem paramétrica. A principal motivação deste trabalho são os recentes incentivos regulatórios que estão fomentando a geração distribuída no Brasil. Contudo, as redes de distribuição convencionais foram projetadas para serem passivas e a introdução da geração poderá causar problemas de ordem técnica que ainda precisam ser resolvidos. Tais problemas foram pesquisados e aqueles relacionados com os impactos sobre as correntes de curto-circuito foram enfatizados. As normas técnicas das concessionárias também foram investigadas porque seus requisitos, como a ligação dos transformadores de acoplamento, influem nas correntes de curto-circuito. Para se calcular as correntes de curto-circuito, desenvolveu-se uma planilha eletrônica cujos resultados foram validados com programas comerciais de análise de redes elétricas. Esta ferramenta foi utilizada para demonstrar, através de exemplos, o impacto causado pela geração distribuída sobre as correntes de curto-circuito e, posteriormente, para realizar as análises paramétricas nas quais a influência de cada variável foi avaliada. A aplicação do método paramétrico permitiu o estudo de possíveis limites para a potência de um gerador distribuído em função dos impactos admissíveis, de seu ponto de conexão, de seus parâmetros elétricos e dos parâmetros elétricos da rede. / The purpose of this thesis is to analyse the impacts of distributed generation on short-circuit currents and protection of the distribution utilities medium voltage networks using a parametric approach. The new regulations that are promoting the distributed generation in Brazil are the main motivation for this work. However, the conventional distribution networks were designed to be passive; therefore the integration of generation may cause some technical problems yet to be solved. Such problems were researched and those related to the impacts on short-circuit currents were emphasized. The utilities technical standards were also explored as their requirements affect the short-circuit currents (e.g. the transformers connections). A spreadsheet was developed in order to calculated the short-circuit currents and it was validated comparing its results to those of a commercial network analysis software. This tool was used to expose the impacts of distributed generation on short-circuit currents through examples and also to carry out parametric analysis in which the influence of every variable was evaluated. The application of a parametric method made it possible to define the maximum installed capacity of a distributed generator as a function of the allowed limits to the impacts on the short-circuit currents, its point of coupling, its electrical parameters and the electrical parameters of the network.