Este trabalho consiste em um estudo sobre alívio de cargas aplicado em indústrias que apresentam sistema misto para geração de energia, na qual uma parte da energia elétrica é gerada através de processo próprio (co-geração) e outra parte é suprida pela alimentação fornecida pelo sistema elétrico regional (concessionária). O alívio de cargas consiste em uma técnica de desligamento rápido e seletivo de algumas cargas, visando manter o sistema em equilíbrio durante interrupção emergencial do fornecimento de energia pela concessionária. Este trabalho efetua uma revisão bibliográfica sobre redes de comunicação, norma IEC 61850, sistemas de supervisão e técnicas de alívio de cargas, as quais se tornam ferramentas que viabilizam o alcance do seu objetivo, que é a proposição de um sistema baseado em um software de supervisão de mercado, que executa seu algoritmo adaptativo de alívio de cargas e pré-sensibiliza equipamentos inteligentes de campo (IEDs), conectados conforme padrões estabelecidos pela norma IEC 61850, para efetuarem o desligamento de algumas cargas de uma indústria com sistema misto de geração, em caso de distúrbio no fornecimento pela concessionária. O diferencial do sistema proposto neste trabalho consiste na capacidade do algoritmo, executado pelo software de supervisão, em simular a ocorrência de eventos que caracterizam perdas na geração de energia e transferir ordens para os IEDs efetuarem os desligamentos de determinadas cargas antes da ocorrência dos desequilíbrios. Dessa forma, a principal contribuição do trabalho é apresentar um sistema preditivo contra possíveis emergências ocorridas na concessionária, ou seja, como o sistema possui ação conjunta entre o algoritmo adaptativo executado pelo software de supervisão e os IEDs, conectados segundo padronizações da norma IEC 61850, oferece capacidade para pré-sensibilizar os desligamentos de cargas antes que ocorram os reais eventos de perda de geração de energia elétrica. / This work consists on a study about load shedding applied to industries that use mixed systems on energy generation, where part of the electrical energy is generated by own process (co-generation) and the other part is supplied by the regional electrical system (concessionaire). The load shedding consists in a rapid and selective shut-off technique aiming to maintain the system under balance during power interruption events from the concessionaire. This work provides a literature survey over communication networks, the IEC 61850 standard, supervisory control and data acquisition systems (SCADA) and load shedding techniques, which become tools that make possible to reach the works goal: to propose a system based on a market SCADA software that runs its load shedding adaptive algorithm and pre-sensitize Intelligent Electronic Devices (IEDs), connected according to preestablished standards by the IEC 6180 norm for shutting off some loads in a company with a mixed generation system in case of some supplying disturb from the concessionaire. The differential of the proposed system in this work consists in the capacity of the algorithm, run by the SCADA software, of simulating the occurrence of events that characterize losses in energy generation and sending commands to the IEDs to shut off specific loads before an unbalance occurs. This way, the main contribution of this work is to present a predictor system against possible emergencies happening in the concessionaire, that is, as the system provides a joint approach between the SCADA systems algorithm and the properly connected IEDs, it provides the capacity of pre-sensitizing the load shedding before real events of electrical energy generation loss occur.

The main objective of this thesis was to develop appropriate system protection schemes against two important causes of failure in power systems, namely, long-term voltage instability and cascade tripping of overloaded transmission lines, mainly due to overloading. To this purpose a distributed undervoltage load shedding scheme against voltage instability, and a centralized protection meant to alleviate line overload are proposed. The former, through the chosen system protection scheme characteristics, has the ability to adjust its actions to the disturbance location and severity. This behavior is achieved without resorting to a dedicated communication network. The distributed controllers do not exchange information, but are rather informed of their respective actions through voltage measurements. Neither do the controllers require a model of the system. This and the absence of communication makes the protection scheme simple and reliable. The other protection scheme, inspired of model predictive control, is aimed at bringing the currents in the overloaded lines below their limits in the time interval left by protections, while accounting for constraints on control changes. Its closed-loop nature allows to compensate for model uncertainties and measurement noise. In order to tune the proposed system protection schemes parameters and validate their performance it was preferred to detect plausible cascading event scenarios. To this purpose, an algorithm meant to identify such complex sequences has been developed. It encompasses hidden failures and the resulting system response. The tests performed on small systems as well as on a real-life one confirm not only that proposed protection schemes appropriately deal with the problems for which they were designed, but also that they cooperate satisfactorily for combined voltage and thermal problems that are beyond their individual capabilities.

In modern power systems, renewable energy has become an increasingly popular form of energy generation as a result of all the rules and regulations that are being implemented towards achieving clean energy worldwide. However, clean energy can have drawbacks in several forms. Wind energy, for example can introduce intermittency. In this thesis, we discuss a method to deal with this intermittency. In particular, by shedding some specific amount of load we can avoid a total system breakdown of the entire power plant. The load shedding method discussed in this thesis utilizes a Markov Decision Process with backward policy iteration. This is based on a probabilistic method that chooses the best load-shedding path that minimizes the expected total cost to ensure no power failure. We compare our results with two control policies, a load-balancing policy and a less-load shedding policy. It is shown that the proposed MDP policy outperforms the other control policies and achieves the minimum total expected cost.

Power distribution systems have underwent a lot of significant changes in the last two decades. Wide-scale integration of Distributed Energy Resources (DERs) have made the distribution grid more resilient to abnormal conditions and severe weather induced outages. These DERs enhance the reliability of the system to bounce back from an abnormal situation rather quickly. However, the conventional notion of a radial system with unidirectional power flow does not hold true due to the addition of these DERs. Bidirectional power flow has challenged the conventional protection schemes in place. The most notable effects on the protection schemes can be seen in the field of islanding or Loss of Mains(LOM) detection and general fault identification and isolation. Adaptive protection schemes are needed to properly resolve these issues. Although, previous works in this field have dealt with this situation, a more comprehensive approach needs to be taken considering multiple topologies for developing adaptive protection schemes. The most common protective devices widely deployed in the distribution system such as overcurrent relays, reverse power relays at Point of Common Coupling(PCC), fuses, reclosers and feeder breakers need to studied in implementing these schemes. The work presented in this dissertation deals with simulation based and analytical approaches to tackle the issues of islanding and adaptive protection schemes. First we propose a multiprinciple passive islanding detection technique which relies on local PCC measurements, thus reducing the need of additional infrastructure and still ensuring limited Non Detection Zone (NDZ). The next step to islanding detection would be to sustain a islanded distribution system in order to reduce the restoration time and still supply power to critical loads. Such an approach to maintain generator load balance upon islanding detection is studied next by appropriate shedding of non-critical and low priority critical loads based upon voltage sensitivity analysis. Thereafter, adaptive protection schemes considering limited communication dependency is studied with properly assigning relay settings in directional overcurrent relays (DOCRs), which are one of the most widely deployed protective devices in distribution systems by catering to multiple topologies and contingencies. A simulation based technique is discussed first and then an analytical approach to solve the conventional optimal relay coordination problem using Mixed Integer Linear Programming (MILP) with the usage of multiple setting groups is studied. All these approaches make the distribution more robust and resilient to system faults and ensure proper fault identification and isolation, ensuring overall safety of system. / Doctor of Philosophy / With widespread integration of inverter-based distributed energy resources (DERs) in the distribution grid, the conventional protection and control schemes no longer hold valid. The necessity of an adaptive protection scheme increases as the DER penetration in the system increases. Apart from this, changes in system topology and variability in DER generation, also change the fault current availability in the system in real-time. Hence, the protection schemes should be able to adapt to these variations and modify their settings for proper selectivity and sensitivity towards faults in the system, especially in systems with high penetration of DERs. These protection schemes need to be modified in order to properly identify and isolate faults in the network as well as correctly identify Loss of Mains (LOM) or islanding phenomenon. Special attention is needed to plan the next course of action after the islanding occurrence. Additionally, the protective devices in distribution system should be utilized to their maximum capability to create an adaptive and smart protection system. This document elaborately explains the research work pertaining to these areas.

AASHTO LRFD requires the use of longitudinal stiffeners in plate girder webs when the web slenderness D/tw is greater than 150. This practice is intended to limit the lateral flexing of the web plate during construction and at service conditions. AASHTO accounts for an increase in the web bend buckling resistance due to the presence of a longitudinal stiffener. However, when the theoretical bend buckling capacity of the stiffened web is exceeded under strength load conditions, the Specifications do not consider any contribution from the longitudinal stiffener to the girder resistance. That is, the AASHTO LRFD web bend buckling strength reduction factor Rb applied in these cases is based on an idealization of the web neglecting the longitudinal stiffener. This deficiency can have significant impact on girder resistance in regions of negative flexure. This research is aimed at evaluating the improvements that may be achieved by fully considering the contribution of web longitudinal stiffeners to the girder flexural resistance. Based on refined FE test simulations, this research establishes that minimum size longitudinal stiffeners, per current AASHTO LRFD requirements, contribute significantly to the post buckling flexural resistance of plate girders, and can bring as much as a 60% increase in the flexural strength of the girder. A simple cross-section Rb model is proposed that can be used to calculate the girder flexural resistance at the yield limit state. This model is developed based on test simulations of straight homogenous girders subjected to pure bending, and is tested extensively and validated for hybrid girders and other limit states. It is found that there is a substantial deviation between the AISC/AASHTO LTB resistance equations and common FE test simulations. Research is conducted to determine the appropriate parameters to use in FE test simulations. Recommended parameters are identified that provide a best fit to the mean of experimental data. Based on FE simulations on unstiffened girders using these recommended parameters, a modified LTB resistance equation is proposed. This equation, used in conjunction with the proposed Rb model also provides an improved handling of combined web buckling and LTB of longitudinally stiffened plate girders. It is observed that the noncompact web slenderness limit in the Specifications, which is an approximation based on nearly rigid edge conditions for the buckling of the web plate in flexure is optimistic for certain cross-sections with narrow flanges. This research establishes that the degree of restraint at the edges of the web depend largely on the relative areas of the adjoining flanges and the area of the web. An improved equation for the noncompact web slenderness limit is proposed which leads to a better understanding and representation of the behavior of these types of members.

Politics in an organisation is an inevitable element in organisation management. The Southern African Development Community (SADC)’s national electricity providers have been subject to an increasingly intense organisational politics cancer for almost two decades, and it is commonly believed to be behind the current electricity generation crisis that has become synonymous within the SADC region. The electricity challenges have spread to most countries in Africa, making the challenge applicable to Africa as a continent. Even on a global scale, electricity crises are increasingly becoming a matter of concern. Economies the world over are known to be heavily reliant on electricity as an energy source. Most if not all economies would be dysfunctional and non-existent without adequate electricity. This study focuses on organisational politics and its impact on managerial practices at a national electricity provider in a SADC region, in particular, Zimbabwe’s national electricity provider and specifically aims to provide a conceptual framework for better cognition and minimisation of negative political behaviour, ultimately enhancing electricity generation capacity for the country. The study is presented in article format covering four areas of study as follows: * Article one identifies the main role-players and their functions in the generation of electrical power at the national electricity providers. The identification of the role-players is literature based and discusses the influences of the role-players in the equation of electricity generation for the economy. A biographical profile of the national electricity provider is compiled by means of an empirical study. * The second article explores and interrogates employees’ perceptions of organisational politics by employing both theoretical and empirical study focusing on the causes/sources of political behaviour at the national electricity provider. * The third article investigates the effects of organisational politics at the national electricity provider focusing on the positive and negative effects. The article also employs both a literature and an empirical study. * The final article provides solutions to the negative effects of organisational politics. It investigates the managerial practices for minimising negative political behaviour through a review of literature as well as undertaking an empirical study. A sample of 1400 participants was randomly selected from the population of 2210 employees, representing 63.35% of the population. A total of 358 completed questionnaires were returned by the cut-off date. Of the 358, 11 were discarded as they were incorrectly completed, giving an effective response rate of 24.78%. The study employed the statistical software programme SPSS 21.0 for Windows to analyse the data. Various quantitative statistical techniques that suit the doctoral level of research were used to analyse the data. The techniques include: * Kaiser-Meyer-Olkin (KMO) measure of sampling adequacy; * Exploratory factor analysis * Bartlett’s test of sphericity; and * Cronbach Alpha’s reliability coefficient. The major findings of the study were: * The first article identified the main role-players within the national electricity provider’s political environment as: employees, managers; government; and board of directors. Central to the political environment, are diverse goals from each role-player which in most cases is incongruent, giving birth to the political tempo (organisational politics) within the organisation. * The second article identified four significant factors perceived as contributing to political behaviour at the national electricity provider. The factors are managerial behaviour, poor communication of objectives, unexpected employee behaviour and unhealthy managerial practices. These factors account for a favourable variance of 74.26. * The third article identified three factors of significance that explain the effects of political behaviour at the national electricity provider. These factors account for a favourable variance of 74.67%, and the factors include positive departmental actions, negative employee actions and personal consequences. * The final article sought to provide measures for minimising negative effects of political behaviour, thus the article identified two factors of importance in minimising negative political behaviour at the national electricity provider. These factors are managerial fairness and managerial participation accounting for 70.11% of the total variance. Organisational politics, by and large, impedes organisational performance and in the case of the national electricity provider, it retards the power utility’s capacity to generate the much needed electrical power. Thus an integrated organisational strategy is required to successfully harness negative political behaviour into some significant positive factors that can create a conducive work environment that enhances performance ultimately increasing productivity levels. While the findings of the study holds true of the fact that some political behaviour factors have a hand in the national electricity provider’s inability to generate adequate electrical power, further research is needed to substantiate these factors in other regions of the national electricity provider within Zimbabwe as well as in SADC countries. A SADC approach encompassing all the member countries can help reduce negative political behaviour in key organisations such as the national electricity providers and other parastatals. The study concludes by proposing a comprehensive conceptual organisational politics management model (OPMM) which can be used by managers at the national electricity providers to reduce negative political behaviour. / PhD (Business Administration), North-West University, Potchefstroom Campus, 2014

Politics in an organisation is an inevitable element in organisation management. The Southern African Development Community (SADC)’s national electricity providers have been subject to an increasingly intense organisational politics cancer for almost two decades, and it is commonly believed to be behind the current electricity generation crisis that has become synonymous within the SADC region. The electricity challenges have spread to most countries in Africa, making the challenge applicable to Africa as a continent. Even on a global scale, electricity crises are increasingly becoming a matter of concern. Economies the world over are known to be heavily reliant on electricity as an energy source. Most if not all economies would be dysfunctional and non-existent without adequate electricity. This study focuses on organisational politics and its impact on managerial practices at a national electricity provider in a SADC region, in particular, Zimbabwe’s national electricity provider and specifically aims to provide a conceptual framework for better cognition and minimisation of negative political behaviour, ultimately enhancing electricity generation capacity for the country. The study is presented in article format covering four areas of study as follows: * Article one identifies the main role-players and their functions in the generation of electrical power at the national electricity providers. The identification of the role-players is literature based and discusses the influences of the role-players in the equation of electricity generation for the economy. A biographical profile of the national electricity provider is compiled by means of an empirical study. * The second article explores and interrogates employees’ perceptions of organisational politics by employing both theoretical and empirical study focusing on the causes/sources of political behaviour at the national electricity provider. * The third article investigates the effects of organisational politics at the national electricity provider focusing on the positive and negative effects. The article also employs both a literature and an empirical study. * The final article provides solutions to the negative effects of organisational politics. It investigates the managerial practices for minimising negative political behaviour through a review of literature as well as undertaking an empirical study. A sample of 1400 participants was randomly selected from the population of 2210 employees, representing 63.35% of the population. A total of 358 completed questionnaires were returned by the cut-off date. Of the 358, 11 were discarded as they were incorrectly completed, giving an effective response rate of 24.78%. The study employed the statistical software programme SPSS 21.0 for Windows to analyse the data. Various quantitative statistical techniques that suit the doctoral level of research were used to analyse the data. The techniques include: * Kaiser-Meyer-Olkin (KMO) measure of sampling adequacy; * Exploratory factor analysis * Bartlett’s test of sphericity; and * Cronbach Alpha’s reliability coefficient. The major findings of the study were: * The first article identified the main role-players within the national electricity provider’s political environment as: employees, managers; government; and board of directors. Central to the political environment, are diverse goals from each role-player which in most cases is incongruent, giving birth to the political tempo (organisational politics) within the organisation. * The second article identified four significant factors perceived as contributing to political behaviour at the national electricity provider. The factors are managerial behaviour, poor communication of objectives, unexpected employee behaviour and unhealthy managerial practices. These factors account for a favourable variance of 74.26. * The third article identified three factors of significance that explain the effects of political behaviour at the national electricity provider. These factors account for a favourable variance of 74.67%, and the factors include positive departmental actions, negative employee actions and personal consequences. * The final article sought to provide measures for minimising negative effects of political behaviour, thus the article identified two factors of importance in minimising negative political behaviour at the national electricity provider. These factors are managerial fairness and managerial participation accounting for 70.11% of the total variance. Organisational politics, by and large, impedes organisational performance and in the case of the national electricity provider, it retards the power utility’s capacity to generate the much needed electrical power. Thus an integrated organisational strategy is required to successfully harness negative political behaviour into some significant positive factors that can create a conducive work environment that enhances performance ultimately increasing productivity levels. While the findings of the study holds true of the fact that some political behaviour factors have a hand in the national electricity provider’s inability to generate adequate electrical power, further research is needed to substantiate these factors in other regions of the national electricity provider within Zimbabwe as well as in SADC countries. A SADC approach encompassing all the member countries can help reduce negative political behaviour in key organisations such as the national electricity providers and other parastatals. The study concludes by proposing a comprehensive conceptual organisational politics management model (OPMM) which can be used by managers at the national electricity providers to reduce negative political behaviour. / PhD (Business Administration), North-West University, Potchefstroom Campus, 2014

As conseqüências e repercussões do recente blecaute de grande escala ocorrido no Brasil em 2009, que afetou as regiões Sudeste, Sul, Centro-Oeste e Nordeste além do Paraguai todo; assim como aqueles que afetaram a região do Norte e Nordeste dos Estados Unidos (2003) e toda Itália, também em 2003, mostraram mais uma vez que na atualidade a sociedade tem uma dependência quase total da energia elétrica. Em todos os casos, a falta de energia elétrica atingiu de forma significativa vários setores da economia, ao passo que sistemas de transporte elétrico, indústrias e hospitais sem sistemas de geração emergencial, instituições acadêmicas, iluminação pública e residencial e, inclusive, sistemas de comunicação, ficaram praticamente inoperantes. Após esses eventos, houve uma busca por algumas alternativas que ofereçam maior confiabilidade no fornecimento de energia elétrica ou, pelo menos, alternativas que ajudem a minimizar o seu impacto. O estabelecimento de sistemas baseados em micro-redes elétricas mostrou-se como uma alternativa que poderia ser utilizada para tal finalidade, de tal forma que não apenas cargas críticas, mas também boa parte das atividades mencionadas poderia continuar operando durante períodos de contingência. Por outro lado, o conceito das micro-redes elétricas tem ganho recentemente maior atenção em virtude da crescente penetração de fontes de geração distribuída e dos incentivos providos pelos governos para promover a geração de energia através de fontes renováveis como por exemplo a energia eólica, solar, biomassa, hidrelétrica, e outras. Nos mais diversos países do mundo, atualmente, populações assentadas em regiões remotas utilizam esquemas baseados em micro-redes elétricas para o suprimento de energia elétrica. Assim, neste trabalho serão apresentados os resultados referentes ao estudo da tecnologia das micro-redes elétricas, especificamente o seu desempenho diante de condições operativas como o modo de operação ilhado e o modo conectado com a rede elétrica. Particularmente, a transição para o modo de operação ilhado demandou um estudo, através das simulações, mais dedicado. No que se refere à negociação da energia entre a micro-rede e a rede principal, quando da disponibilidade de energia excedente nos períodos de carga reduzida na micro-rede, será apresentada uma análise crítica dos possíveis métodos de tarifação, os quais até agora são apenas utilizados na forma de incentivos governamentais. Será também apresentada uma análise referente à viabilidade econômica de micro-redes, já que para que estas tenham atratividade econômica, os custos de aquisição de equipamentos e operação devem também ser competitivos. / After the occurrence of some major blackouts like the one that affected the Northern and Northeastern part of the United States in 2003, the one that affected the Southeast, Midwest and Northeastern part of Brazil including Paraguay, in 2009; and the blackout that affected the whole Italy in 2003, to mention a few a few of them, there was a rush for seeking some alternatives to deal with such events or at least find out feasible solutions that can contribute to diminish their impact. The lack of electric power, for whatever reason it was, unveiled one common fact, our modern society is so dependent on electricity that during the blackouts areas like the electrical transport system, financing activity, academic institutions, industries, health centers with no emergency or standby generation, public and residential lighting and even some communication systems failed to operate. The establishment of microgrid systems proved to be an alternative that could be used for this purpose; thus, not only critical loads, but also some of the activities mentioned earlier on could continue their operation during such emergency periods. In addition, the concept of micro-grid systems has recently gained particular attention due to the increasing penetration of distributed generation and also due to the incentives provided by the governments to promote the generation of electricity from renewable sources such as wind power, solar, biomass, small hydroelectric schemes, etc. At present, countless settlements located in remote areas worldwide use microgrid systems to generate and distribute electricity. In this work, the results related to the microgrid technology, specifically its performance towards system conditions such as the islanding mode and grid connected mode of operation will be presented. Particularly, the transition to the islanded mode of operation demanded a more dedicated study during the simulations performed. As for the energy trading between the microgrid and the utility, which can occur when the microgrid generators are lightly loaded, it will be presented a critical analysis about the possible tariff methods to be applied. Such tariffs are so far only applied in the form of government subsidies to promote the use of renewable energy sources. Additionally, an analysis of a microgrid economic feasibility to show how competitive or complimentary this technology is with the utility will be presented herein.

In the context of static Voltage Stability Assessment (VSA), as the power system load grows, bus voltages tend to drop. This reduction may lead to generator or load disconnections caused by undervoltage protection schemes. These events comprise sudden parametric variations that affect the equilibrium diagram and the Voltage Stability Margin (VSM) of power systems. Practical examples of such sudden load changes are caused by the mandatory disconnection of Distributed Generation (DG) units and Undervoltage Load Shedding (ULS). There are no thorough studies in the literature concerning these load parametric variations and the discontinuities that they cause in power system equilibria. This dissertation describes a predictor/corrector scheme specifically designed to handle these discontinuities, so it is possible to evaluate their effect on the VSM of power systems. This method successively calculates the load discontinuities that exist in the equilibrium locus of the system under analysis. It results in the sequence of sudden load variations that happens and their overall impact on the system. When applied to quantify the effect of DG mandatory disconnections and ULS, the proposed predictor/corrector scheme yielded better results than the traditional Continuation Power Flow (CPFLOW), which experienced convergence problems caused by the discontinuities under analysis. However, due to its design, the applicability of the proposed method should be restricted to power systems that go through several successive sudden load changes. In this sense, it should not be regarded as a replacement for the CPFLOW, but rather as a technique that could award this traditional VSA tool with new features to enhance its performance. / No contexto de análise estática de estabilidade de tensão, conforme a carga de um sistema de potência cresce, as tensões nas suas barras tendem a cair. Essa redução pode causar a desconexão de geradores e cargas devido a atuação de proteções de subtensão. Esses eventos representam variações abruptas de demanda que alteram o diagrama de equilíbrio de um sistema e sua Margem de Estabilidade de Tensão (MET). Exemplos práticos dessas variações são causados pelo desligamento mandatório de unidades de Geração Distribuída (GD) e pelo Corte de Carga por Subtensão (CCS). Não há estudos detalhados na literatura que trabalham especificamente com essas variações nos parâmetros da carga, nem com as descontinuidades que elas causam no diagrama de equilíbrio de sistemas de potência. Essa dissertação descreve um procedimento especificamente projetado para lidar com essas descontinuidades, de modo que seja possível avaliar seu efeito na MET de sistemas elétricos. Esse método calcula sucessivamente as descontinuidades de carga que existem no diagrama de equilíbrio do sistema em análise. Ele resulta na sequência de variações súbitas de carga que ocorre e no seu impacto no sistema. Quando o método foi aplicado para quantificar o efeito do desligamento mandatório de GD e do CCS, ele apresentou resultados melhores do que o tradicional Fluxo de Carga Continuado (CPFLOW), o qual sofreu problemas de convergência causados pelas descontinuidades em questão. Entretanto, devido ao seu projeto, o método proposto só deve ser utilizado para sistemas de potência que estão sujeitos a várias sucessivas variações abruptas de carga. Por essa razão, esse método não pode ser considerado um substituto do CPFLOW, mas sim como uma técnica capaz de agregar novas funcionalidades a essa ferramenta tradicional, amentando assim seu horizonte de aplicações.

O objetivo desta tese é desenvolver e implementar em computador uma metodologia para resolver o problema de alívio de carregamento utilizando técnicas de remanejamento ou corte de carga. Tal metodologia, fundamenta-se no Algoritmo Evolutivo Multiobjetivo em Tabelas, que foi desenvolvido inicialmente para o problema de restabelecimento de energia em sistemas de distribuição. Já metodologia desenvolvida nesta tese trata o problema de alívio de carregamento, buscando minimizar o número de consumidores sem fornecimento de energia elétrica e o número de operações de chaveamento. Todavia, é necessário a obtenção de um plano de manobras em chaves adequado de modo que este não inviabilize a implantação na prática e que resulte em soluções que contemplem: a ausência de sobrecarga na rede e nas subestações, a manutenção dos níveis de tensão dentro dos intervalos exigidos pela legislação e a manutenção da radialidade da rede. Para alcançar estes objetivos, utiliza-se técnicas que determinam a sequência de chaveamento necessária para o plano de alívio de carga obtido. Prioriza-se, ainda, o atendimento aos consumidores prioritários e o corte seletivo de cargas em condições de esgotamento das possibilidades de remanejamento entre os alimentadores primários. Ao aplicar a metodologia proposta em um sistema de distribuição real de grande porte da Companhia Energética de Pernambuco - CELPE, constatou-se que, em comparação com a técnica atualmente utilizada, a metologia desenvolvida é confiável e apresenta bons resultados no que se refere a: sequência exequível de manobras, diminuição do número de chaveamentos e redução do número de consumidores e consumidores prioritários sem atendimento. Além disso, a metodologia possui capacidade de aplicação em outros sistemas semelhantes e foi integrada em um sistema computacional com ambiente gráfico permitindo estudos de caso e armazenamento em banco de dados. / The objective of this research is to develop and implement a methodology for the treatment of load shedding problem due to the existence (operation) or the possibility to occur (planning) contingencies in supply system (High Voltage/Subtransmission). The methodology is based on Multiobjective Evolutionary Algorithm in Tables, initially developed for the service restoration problems in distribution systems. It aims to minimize the number of customers without electricity supply; minimizing the number of switching operations, so that it does not impede the implementation in practice; absence of overload in network and substations; maintaining the voltage levels within the ranges required by the laws of radiality and maintenance of the network. To achieve these goals, are used techniques for determining the required switching sequence for the load shedding plan obtained; prioritization of special consumer in service and selective load shedding when exhausted the possibilities of relocating loads between primary feeders. When applies the proposed methodology in a real large distribution system of the Energy Company of Pernambuco - CELPE, it can be seen that, compared with the technique currently used, it is reliable with good results regarding viable sequence of maneuvers; reducing the number of switchings and number of consumers and priority consumers without service in addition to be able to be applied in similar systems. The methodology has been integrated into a computer system in a graphical environment with facilities of case studies and storing information in the database.