The aim of this study was to evaluate the ability of the antioxidant myricetin to protect ovine spermatozoa during freezing-thawing. Five semen pools, obtained from four rams, were diluted and frozen in Tris-egg yolk extender (5% glycerol) supplemented with myricetin at 0, 20, 30, 40, 100, 200, 300, and 400 nM. After thawing at 37 °C for 30 seconds and incubation (37 °C) for two hours, these variables were measured: kinematics, plasma and acrosome membrane integrity, mitochondrial membrane potential, intracellular reactive oxygen species (ROS) levels, lipid peroxidation and membrane stability. There was no interaction between treatment and time, and no direct effect of treatments for the kinematics parameters (P >0.09; P >0.2113, respectively) and flow cytometry (P >0.41; P > 0.52, respectively). The means of progressive motility, curvilinear velocity, straight-line velocity, average path velocity, linearity, amplitude of lateral head displacement, percentage of intact plasma membrane and acrosome membrane, oxidative stress and membrane stability were reduced during incubation (P <0.04), whereas the cross-beat frequency increased (P =0.0001) throughout incubation. Thus, the addition of myricetin to the semen extender does not produce an antioxidant effect on ram semen in vitro.

RESUMO Objetivou-se avaliar o efeito de diferentes concentrações de (+)-catequina ou (-)-epigalocatequina galato (EGCG) sobre a congelabilidade do sêmen caprino. Poolsseminais foram processados (experimento 1: 0, 15, 25, 50, 75 ou 100µM de (+)-catequina; experimento 2: 0, 15, 25, 50, 75 ou 100µM de EGCG) e congelados. Após a descongelação, foram avaliadas a cinética, a integridade de membrana plasmática (iMP) e acrossomal, a morfologia e o estresse oxidativo, a zero e a uma hora. No experimento 1, a zero hora, VSL e VAP foram maiores (P<0,05) com 15µM do que com 50 e100; WOB foi menor (P<0,05) com 100µM do que com 0, 15 e 25; e BCF foi maior (P<0,05) com 75 e 100µM do que com 0. No experimento 2, a motilidade progressiva foi maior (P<0,05) com 0 e 15µM do que com 50 e 75; LIN foi menor (P<0,05) com 75 e 100µM do que com 0 e 15; WOB foi maior (P<0,05) com 0 e 15µM; e iMP foi maior (P<0,05) com 100µM do que com 0. Assim, (+)-catequina ou EGCG em altas concentrações inibem, transitoriamente, a cinética de espermatozoides congelados caprinos, e 100µM de EGCG preserva a iMP.

ABSTRACT The aim of this study was to evaluate the effects of different concentrations of (+)-catechin or (-)-epigallocatechin gallate (EGCG) on goat semen freezability. Poolsof semen were processed (Experiment 1: 0, 15, 25, 50, 75, or 100µM (+)-catechin; Experiment 2: 0, 15, 25, 50, 75, or 100µM EGCG) and frozen. After thawing, the samples were evaluated for kinematics, plasma membrane (PMi) and acrosome integrity, morphology, and oxidative stress, at 0 and 1h. In Experiment 1, at 0h, VSL and VAP were greater (P<0.05) with 15µM than with 50 and 100; WOB was lower (P<0.05) with 100µM than with 0, 15, and 25; and BCF was higher (P<0.05) with 75 and 100µM than with 0. In turn, in Experiment 2, progressive motility was higher (P<0.05) with0 and 15µM than with50 and 75; LIN was lower (P<0.05) with75 and100µM than with0 and 15; WOB was higher (P<0.05) with0 and 15µM; and PMi was greater (P<0.05) with100µM than 0. Thus, (+)-catechin or EGCG at higher concentrations inhibits the kinematics of frozen goat sperm, in a transitory way, and 100µM of EGCG preserves the PMi.

This study was conducted to evaluate the effects of lycopene on quality parameters of cryopreserved ram semen. Semen samples were collected from three Santa Inês rams to form a seminal pool (n = 8). Aliquots from each pool were diluted in Tris-egg yolk extender to create experimental groups containing 0 μΜ (control), 0.1 μΜ, 1 μΜ and 5 μΜ lycopene. The samples were evaluated for sperm kinetics, integrity of plasma and acrosomal membranes, intracellular reactive oxygen species (ROS) production and lipid peroxidation immediately after thawing and after incubation for two hours at 37 °C. The addition of lycopene had no effect on the parameters that were evaluated at the time of thawing when compared with the control. However, after incubation, the groups with added lycopene showed a decrease in progressive motility. All experimental groups showed a significant reduction in linearity and straightness following incubation. Furthermore, the 5 μΜ lycopene group showed a decrease in wobble and an increase in amplitude of lateral head displacement. In conclusion, the addition of lycopene to the freezing extender of ram semen affected the kinetics parameters of cryopreserved spermatozoa after a two-hour incubation period.

The aim of this study was to evaluate the therapeutic effects of ultrasound (US)-mediated phonophoresis alone or in association with diclofenac diethylammonium (DCF) administered topically in animal models of inflammation. A pre-clinical, prospective, and randomized experimental study of quantitative and qualitative nature was carried out. Phonophoresis was performed using a therapeutic ultrasound apparatus in two distinct models of acute inflammation. Edema was induced by an intraplantar injection of carrageenan and measured by plethysmography. The Hargreaves test was used to evaluate the antinociceptive activity and investigate the action of phonophoresis on tumor necrosis factor (TNF)-α production. A histological analysis with hematoxylin-eosin was used to evaluate tissue repair, and the expression of COX-2 was determined by immunohistochemical analysis. At the peak of inflammatory activity (3 h), treatment with US, US+DCF, and DCF significantly reduced edema formation compared to the control group. Treatment with US+DCF was more effective than treatment with US alone at both analyzed times. In the analysis of the antinociceptive activity, the treatments significantly increased the latency time in response to the thermal stimulus. Histopathological analysis revealed a reduction of the inflammatory infiltrates and immunohistochemistry demonstrated that the association was effective in reducing COX-2 expression compared to the control group. The association of DCF with US produced anti-inflammatory and antinociceptive effects in rat models of inflammation, which may be associated with inhibition of COX-2 and TNF-α production.

RESUMO O objetivo deste estudo foi avaliar o efeito da suplementação do diluidor de congelação de sêmen ovino com o flavonoide miricetina contra os danos ocasionados aos espermatozoides. Oito pools de sêmen, obtidos de quatro reprodutores ovinos, foram congelados com diferentes concentrações de miricetina (0, 1, 10, 100 e 1000nM). Após o descongelamento, o sêmen foi avaliado quanto à cinética espermática, à integridade das membranas plasmática e acrossomal, ao potencial de membrana mitocondrial, aos níveis de ROS intracelular, à peroxidação lipídica e à estabilidade de membrana. Amostras tratadas com miricetina 10nM apresentaram menor percentual de células rápidas (P≤0,05), quando comparadas ao grupo miricetina 1000nM. Amostras do grupo controle apresentaram maior (P≤0,05) VAP que o grupo 10nM de miricetina, enquanto amostras criopreservadas com miricetina (10, 100 e 1000nM) evidenciaram maior (P<0,05) BCF, quando comparadas ao grupo controle. O grupo tratado com miricetina 1000nM apresentou maior percentual (P<0,05) de células com peroxidação lipídica, quando comparado ao grupo controle. Em conclusão, a suplementação do diluidor de criopreservação de sêmen ovino com 10 e 100nM de miricetina afeta a cinética espermática sem provocar alterações na estrutura geral do gameta, enquanto 1000nM de miricetina provoca mudanças na cinética associadas à danos peroxidativos.

ABSTRACT The aim of this study was to evaluate the effect of the supplementation of ram semen frozen with extender with the flavonoid myricetin against damage to sperm. Eight pools of semen obtained from four ram breeders, were frozen with different concentrations of myicetin (0, 1, 10, 100 and 1000nM). After thawing, the semen was evaluated for spermatic kinetics, plasma and acrosome membrane integrity, mitochondrial membrane potential, intracellular ROS levels, lipid peroxidation, and membrane stability. Samples treated with 10nM myricetin preserved a lower percentage of rapid cells (P≤0.05) when compared to the 1000nM myricetin group. Samples from the control group presented higher (P≤0.05) VAP than 10nM group of myricetin, while cryopreserved samples with myicetin (10, 100 and 1000nM) showed greater (P<0.05) BCF, when compared to control group. The group treated with 1000nM myricetin had a higher percentage (P<0.05) of cells with lipid peroxidation, when compared to the control group. In conclusion, supplementation of ram semen cryopreservation extender with 10 and 100nM myricetin affects sperm kinetics, without causing changes in the overall structure of the gamete, while 1000nM myricetin causes changes in the kinetics associated with peroxidative damage.

RESUMO Ensaios de Velocidade de Propagação de Pulso Ultrassônico (VPU) são cada vez mais usados para detectar falhas em concreto. Este trabalho é parte de um programa experimental amplo que buscou estudar a influência de variáveis-chave na capacidade de detecção usando ensaios de VPU em elementos de escala natural. Para essa investigação foram moldados dois elementos de concreto de larga escala, com vários objetos introduzidos em um deles para simular possíveis falhas de concretagem. Ademais, para verificar a capacidade de identificação de vazios não-aparentes com a técnica de VPU, perfurações graduais em diferentes profundidades foram feitas a partir da face não monitorada. Os resultados confirmam que o ensaio de VPU é uma ferramenta adequada para detecção de falhas no concreto, até certa profundidade.

ABSTRACT Ultrasonic Pulse Velocity (UPV) tests are being increasingly used to detect flaws in concrete. This work is part of a large experimental program aimed at studying the influence of key technological variables on detection capacity using UPV in real size elements. For this investigation two large concrete elements were cast, with some objects introduced in one to simulate possible concrete flaws due to inadequate casting. Furthermore, to check the capacity of detecting unseen voids with UPV tests, gradual perforations with different depths were made from the unmonitored face. The results confirm that UPV analysis is a very good tool to detect concrete faults, up to some depth.

RESUMEN Los ensayos de Velocidad de Propagación del Pulso Ultrasónico (VPU) vienen siendo cada vez más empleados para detectar fallas in hormigón. Este trabajo es parte de una amplia investigación experimental que tiene el objetivo de estudiar la influencia de variables tecnológicas claves en la capacidad de detección del UPV in elementos de tamaño real. Para esa pesquisa dos elementos largos de concreto fueran moldeados, con objetos introducidos para simular fallas en el hormigón. Además, para chequear la capacidad de detección de vacíos no visibles de la técnica de VPU, se realizaron perforaciones graduales hasta diferentes profundidades, empezando en la cara no monitoreada. Los resultados confirman que el ensayo de VPU es una herramienta muy buena para detección de fallas, hasta cierta profundidad.

Resumo A aplicação de Ensaios Não Destrutivos (END) é uma estratégia interessante para monitorar o estado de conservação das estruturas de concreto armado, principalmente quando ocorrem erros de dosagem, problemas na mistura, transporte ou lançamento do concreto. Dentre os métodos de END, aplicáveis ao concreto, o método de ensaio da Velocidade de Propagação do Pulso Ultrassônico (VPU) vem sendo utilizado comumente em diversas áreas da Engenharia Civil, devido à facilidade da operação, ao seu baixo custo, à rapidez na execução dos testes e à ausência de danos ao material analisado. Este trabalho visa estudar a influência que determinadas variáveis tecnológicas exercem sobre os resultados obtidos através dos ensaios de VPU. Foram moldados em laboratório dois elementos de concreto, com dimensões próximas a estruturas reais. Um elemento com armadura nas duas faces e outro sem armadura, nos quais foram introduzidos objetos para reproduzir possíveis falhas de concretagem. De modo a facilitar a análise dos dados, os resultados são apresentados por meio de imagens geradas através de programas computacionais e análises estatísticas. Através deste estudo verificou-se que a escolha dos parâmetros de ensaios é fator crucial para que se tenha uma interpretação correta dos resultados.

Abstract The application of Nondestructive Testing methods (NDT) may be an interesting strategy to monitor the condition state of reinforced concrete structures, especially when there are problems related to mixing, conveying or placing the concrete. Among the NDT methods, the Ultrasonic Pulse Velocity (UPV) has been one of the most used in various fields of civil engineering, due to the ease of operation, low cost, test velocity and low level of damage to the surface analyzed. This work aims to study the influence of certain technological variables in the results obtained through UPV tests. With this aim two large blocks were cast at the laboratory, with dimensions close to real concrete elements. One of the elements was reinforcement with steel meshes on both sides while the other was cast without reinforcement. Inside these elements objects were introduced to reproduce internal concrete flaws. To facilitate the analysis the results were represented by means of a surface mapping image technique and were also subjected to statistical analysis. Through the study it was demonstrated that the correct choice of test parameters is crucial to obtain a right interpretation of UPV results from real structures.

RESUMO O objetivo deste estudo foi avaliar o efeito de diferentes concentrações de transresveratrol ou quercetina sobre a capacidade dos espermatozoides caprinos de resistirem à congelação. Seis pools de sêmen, obtidos de seis reprodutores caprinos, foram processados com diferentes concentrações de resveratrol ou quercetina (Experimento 1: 0, 15, 25, 50, 75 ou 100μM de resveratrol; Experimento 2: 0, 15, 25, 50, 75 ou 100μM de quercetina) e congelados. Após o descongelamento, o sêmen foi avaliado quanto à cinética espermática, à integridade das membranas plasmática e acrossomal, à morfologia e ao estresse oxidativo nos tempos zero e uma hora de incubação. Imediatamente após a descongelação (zero hora), o wobble (índice de oscilação) nos grupos tratados com 100μM de quercetina ou de resveratrol foi menor (P<0,05) do que nos tratados com 0 e 25μM de resveratrol e com 0μM de quercetina, respectivamente. Após uma hora de incubação, a motilidade total dos tratamentos com 15, 50 e 75µM de quercetina, assim como a integridade de membrana plasmática em todas as concentrações de quercetina, foi menor (P<0,05) do que à zero hora. Em oposição, a linearidade das amostras de sêmen tratadas com 100µM de quercetina e a retilinearidade daquelas tratadas com 75µM e 100µM de quercetina foram menores (P<0,05) à zero hora do que à uma hora após descongelação. Assim, pode-se concluir que o resveratrol e a quercetina, em concentrações elevadas (100μM), reduzem, transitoriamente, o índice de oscilação de espermatozoides caprinos submetidos à congelação e que a quercetina (75 e 100µM) aumenta a linearidade e a retilinearidade ao longo do tempo, o que pode ser favorável à fertilidade.

ABSTRACT The aim of this study was to evaluate the effect of different concentrations of trans-resveratrol or quercetin on the ability of goat sperm to withstand being frozen. Six pools of semen obtained from six male goats were processed with different concentrations of resveratrol or quercetin (Experiment 1: 0, 15, 25, 50, 75 or 100µM resveratrol; Experiment 2: 0, 15, 25, 50, 75 or 100µM quercetin) and frozen. After thawing, the semen was evaluated for sperm kinematics, plasma membrane and acrosome integrity, morphology and oxidative stress following 0 and 1h of incubation. Immediately after thawing (0h), wobble (oscillation index) in the groups treated with 100µM of quercetin or resveratrol was lower (P<0.05) than in those treated with 0 and 25µM resveratrol and 0µM quercetin, respectively. After 1h of incubation, the total motility in treatments with 15, 50 and 75µM quercetin, as well as the plasma membrane integrity in all quercetin concentrations were lower (P<0.05) than at 0h. In opposition, the linearity of semen samples treated with 100µM quercetin and the straightness of those treated with 75 and 100µM quercetin were lower (P<0.05) at 0h than at 1h after thawing. Thus, it can be concluded that resveratrol and quercetin at high concentrations (100µM) transiently reduce the wobble of goat sperm submitted to frozen storage, and that quercetin (75 and 100µM) increases the linearity and straightness over time, which can be favorable for fertility.

Recognition of pathogens is performed by specific receptors in cells of the innate immune system, which may undergo modulation during the continuum of clinical manifestations of sepsis. Monocytes and neutrophils play a key role in host defense by sensing and destroying microorganisms. This study aimed to evaluate the expression of CD14 receptors on monocytes; CD66b and CXCR2 receptors on neutrophils; and TLR2, TLR4, TLR5, TLR9, and CD11b receptors on both cell types of septic patients. Seventy-seven septic patients (SP) and 40 healthy volunteers (HV) were included in the study, and blood samples were collected on day zero (D0) and after 7 days of therapy (D7). Evaluation of the cellular receptors was carried out by flow cytometry. Expression of CD14 on monocytes and of CD11b and CXCR2 on neutrophils from SP was lower than that from HV. Conversely, expression of TLR5 on monocytes and neutrophils was higher in SP compared with HV. Expression of TLR2 on the surface of neutrophils and that of TLR5 on monocytes and neutrophils of SP was lower at D7 than at D0. In addition, SP who survived showed reduced expression of TLR2 and TLR4 on the surface of neutrophils at D7 compared to D0. Expression of CXCR2 for surviving patients was higher at follow-up compared to baseline. We conclude that expression of recognition and cell signaling receptors is differentially regulated between SP and HV depending on the receptor being evaluated.

Espécies vegetais da família Apiaceae podem proporcionar recursos vitais para insetos predadores de pragas agrícolas, promovendo sua eficiência como agentes de controle biológico devido à oferta de recursos como sítios de refúgio, proteção e alimentação. Assim, o objetivo deste trabalho foi avaliar a atração de insetos predadores pelas apiáceas coentro (Coriandrum sativum L.), endro (Anethum graveolens L.) e funcho (Foeniculum vulgare Mill.). O experimento foi conduzido no campus da Universidade Federal de Lavras (UFLA), Lavras, MG, em blocos completos ao acaso, com três tratamentos e quatro repetições. Coletas semanais foram realizadas por meio de batida das plantas em bandejas, sendo os predadores aspirados e acondicionados em frascos com álcool 70%. Determinaram-se a curva do coletor, a riqueza de espécies, o índice de diversidade de Shannon-Wienner e o índice de similaridade (análise de Cluster). O funcho apresentou maior índice de Shannon-Wienner (H' = 1,104) e riqueza, enquanto o coentro mostrou maior abundância, sobretudo para a espécie Orius insidiosus (Hemiptera: Anthocoridae), um importante predador de tripes em hortaliças. Outras espécies predadoras de pragas de hortaliças foram encontradas, de maneira geral, em todas as apiáceas, destacando-se os adultos e larvas de coccinelídeos, importantes predadores de pulgões. A análise de Cluster indicou maior similaridade entre funcho e endro (55,03%). O período de floração promoveu considerável aumento na abundância de predadores, sobretudo no coentro.

Species of plants of the Apiaceae family can provide vital resources for predators of agricultural pests, boosting their efficiency as biological control agents, because they allow their maintenance in the environment by offering features such as sites of refuge, protection and food. The present study was aimed to evaluate the attraction of predator insects by 3 Apiaceae species, namely coriander (Coriandrum sativum L.), dill (Anethum graveolens L.) and fennel (Foeniculum vulgare Mill.). The bioassay was conducted on the campus of UFLA (MG) in a randomized block design with 3 treatments and 4 replications. Weekly collections were carried out by beating the plants on white plastic trays, aspirating the predators and packing them into bottles with 70% alcohol. Determinations were made of the collector curve, the species richness, the Shannon-Wienner diversity index and the index of similarity (cluster analysis). The fennel had a higher richness and Shannon-Wienner index (H' = 1.104), while the coriander was more abundant, especially for the species Orius insidiosus (Hemiptera: Anthocoridae), a major predator of thrips in vegetables. Other predatory species of vegetable pests were found, generally, on all Apiaceae, especially adults and larvae of coccinellids, which are important predators of aphids. Cluster analysis indicated a greater similarity between fennel and dill (55.03%), and a lower value for the other pairs. The flowering period increased the abundance of predators, especially the coriander.

A seven month old female goat showed neck swelling, apathy, appetite and weight loss, restlessness, increased salivation, cough, and regurgitation episodes which occurred post feeding. The animal was evaluated through both clinical and radiographic examinations. Plain radiography was performed and contrasted X-ray was done using barium sulfate. For radiological examination, the lateral projection was used for analysis. The results showed a radiopaque content in the esophageal lumen dorsally positioned to heart with density and appearance similar to the rumen. A dilation of the esophagus was reported and a diagnosis of megaesophagus was made. In conclusion, contrast esophagography must be included in the diagnosis of megaesophagus in goats.

Foi avaliada a reparação óssea após implantação de proteínas morfogenéticas ósseas (BMP) em diferentes concentrações e períodos de observação, carreadas por auto-enxerto ósseo esponjoso (EOE), em falhas ósseas, produzidas na região fronto-parietal do crânio de 20 coelhas. A falha I não foi preenchida, a II foi completamente preenchida com 3mg de EOE e as falhas III, IV, V e VI foram preenchidas com EOE associado a 0,5; 1; 2 e 5mg de BMP, respectivamente. Nas avaliações mesoscópicas, post mortem, verificou-se que, independentemente do período de tratamento, o preenchimento ósseo iniciou-se a partir das bordas para o centro e do fundo para a superfície das falhas. Na falha I manifestou-se o menor preenchimento ósseo quando comparada com as demais falhas, em todos os períodos, e nas que receberam 2mg de BMP exibiu-se a melhor cobertura óssea. Microscopicamente, verificou-se que, aos sete dias, o preenchimento ósseo iniciou-se a partir das bordas e do fundo da lesão, com mobilização e diferenciação de células provenientes do periósteo e das meninges, respectivamente e, nas avaliações subseqüentes, a atividade osteoblástica originou-se, também, de "ilhas de ossificação" semelhantes a centros de ossificação, localizadas no centro da falha. A formação trabecular aumentou, proporcionalmente, com a concentração utilizada de BMP, e a aposição e organização óssea aumentaram com o tempo de observação. Verificou-se também a presença de tecido cartilaginoso. A BMP associada ao EOE contribuiu para a formação de novo tecido ósseo, promovendo maior mobilização, diferenciação e organização celular, e abreviou o tempo de formação óssea, sugerindo processo de ossificação endocondral. Os melhores resultados foram observados com a associação de 2mg de BMP a 3mg de enxerto, e a adição de BMP, mesmo em menor quantidade, determinou precocidade de formação óssea. A maior quantidade de BMP não determinou maior preenchimento ósseo.

Aspects of bone repair were evaluated after implantation of bone morphogenetic proteins (BMP) in different concentrations. They were carried by autogenous bone graft in defects created on skulls of 20 adult, young female rabbits, randomizedly divided into five experimental groups and were observed at five times. After exposure of skull bones, six bone defects on the fronto-parietal region of each animal were performed. The defect I was not filled, the II was completed filled with 3mg of autogenous bone graft and the defects III, IV, V, and VI were filled with autogenous bone graft associated with 0.5; 1; 2 and 5mg of BMP, respectively. In the post-mortem mesoscopic evaluations, it was observed that, independently of the treatment period of the defects, the bony filling began from the borders to the center, and from the botton to the surface of the lessions. The bony filling of the defect I was the smallest when compared with the others defects, in all the observation moments. It was also verified that until 2mg the higher the concentration of BMP used, better was the bone cover. Microscopically, it was verified in the first evaluations, on the seventh day, that the bony growth started from the borders and from the bottom of the lesion, with mobilization and differentiation of cells deriving from the periosteum and the meninges, respectively. In the subsequent evaluations, the osteoblastic activity also derived from "ossification islands" to ossification centers, located in the center of the flaw. The trabecular formation increased proportionally with the concentration of BMP used, and the apposition and bony organization increased proportionally with the time of observation. The presence of cartilaginous tissue was verified in all the flaws. In conclusion, the use the higher concentration of BMP did not determinate the better new bone formation. The association of BMP with autogenous bone graft contributed to the formation of new bony tissue, promoting larger mobilization, differentiation, and cellular organization. It also shortened the time of bony formation, suggesting an endocondral ossification process. The better quantities relation was 3mg of autogenous bone graft and 2mg of BMP. The addiction of BMP, even so in low concentration, collaborated to early formation of new bone.

Este trabalho apresenta um método para a análise estática de contingências em Sistemas Elétricos de Potência utilizando o Método da Continuação. A margem de carregamento pós-contingência é obtida a partir do ponto de máximo carregamento do caso base. A magnitude de tensão de uma barra qualquer é usada como parâmetro na etapa de parametrização do fluxo de carga continuado. O ramo selecionado para avaliação da contingência é parametrizado por um fator de escalonamento que possibilita a remoção gradual do ramo e assegura a convergência nos casos em que o método diverge para a retirada total da linha de transmissão. Em geral, para a maioria das contingências analisadas são necessárias poucas iterações para a determinação do ponto de máximo carregamento pós-contingência. Mostra-se que o método pode ser usado como uma técnica alternativa para a averiguação e até mesmo para a obtenção da lista de contingências críticas fornecida pela função de análise de segurança de sistemas elétricos.

This work presents a new methodology for static contingency analysis of electric power systems by using Continuation Methods. The post-contingency loading margin is obtained from the base case maximum loading point. The voltage magnitude of any bus can be used as a parameter in the parameterization step of the proposed continuation power flow. The branch selected for contingency evaluation is parameterized by a scaling factor which allows its the gradual removal and assures the continuation power flow convergence for the cases where the method would diverge for the complete transmission line removal. In general, for most of the analyzed contingencies little iterations are necessary for the determination of the post-contingency maximum loading point. It is shown that the method can be used as an alternative technique to verify and even to obtain the list of critical contingencies supplied by the electric power systems security analysis function.

Os métodos de fluxo de carga por Newton-Raphson e fluxo de carga desacoplado rápido convencionais são considerados inadequados para a obtenção do ponto de máximo carregamento de sistemas de potência, devido à problemas de mal-condicionamento neste ponto crítico e na sua vizinhança. Neste ponto a matriz Jacobiana do método de Newton-Raphson torna-se singular e considera-se que não são mais válidas as hipóteses de desacoplamento P-V e Q-teta utilizadas para a formulação do método fluxo de carga desacoplado rápido. No entanto, mostra-se neste trabalho, que com pequenas modificações, as versões XB e BX do fluxo de carga desacoplado rápido tornam-se adequadas para a obtenção do ponto de máximo carregamento. Estas novas versões modificadas são comparadas entre si com o intuito de explicitar suas características, assim como da influência da atuação dos limites de geração de potência reativa e de tap's de transformadores. Os resultados obtidos para os sistemas testes do IEEE (14, 30, 57 e 118 barras) mostram que as características de convergência das versões originais são preservadas. Além disso, durante o traçado das curvas PV, os diversos métodos podem ser comutados entre si possibilitando o cálculo de todos os pontos da curva com um número reduzido de iterações.

The conventional Newton and fast decoupled load flow methods are considered to be inadequate to obtain the maximum loading point due to ill-conditioning problems at and near this critical point. At this point the Jacobian matrix of the Newton-Raphson method becomes singular, and it is believed that the P-V and Q-theta decoupling assumptions made for the fast decoupled load flow formulation no longer apply. However, as shown in this paper, with small modifications the fast decoupled load flow versions (XB and BX) become adequate for the computation of the maximum loading point. These new modified versions are compared to each other with the purpose of pointing out their features, as well as the influence of reactive power and transformer tap limits. The results obtained for the IEEE systems (14, 30, 57 and 118 buses) show that the convergence characteristics of the conventional versions are preserved. In addition, it is shown that these methods can be switched during the tracing process in order to efficiently determine all the PV curve points with few iterations.

O método de fluxo de carga convencional é considerado inadequado para se obter o ponto de máximo carregamento (PMC) de sistemas de potência, devido à singularidade da matriz Jacobiana neste ponto. Os métodos da continuação são ferramentas eficientes para a solução deste tipo de problema, visto que técnicas de parametrização podem ser utilizadas para evitar a singularidade da matriz Jacobiana. Neste trabalho, novas opções para a etapa de parametrização do método da continuação são apresentadas. Mostra-se que variáveis com claro significado físico podem ser utilizadas na etapa de parametrização. As seguintes variáveis foram testadas: perda total de potência ativa e reativa, potência ativa e reativa na barra de referência, potência reativa das barras de geração, e as perdas de potência ativa e reativa nas linhas de transmissão (LT). Além de facilitar a implementação computacional do método de continuação, as técnicas de parametrização apresentadas simplificam a definição matemática e o entendimento do método por parte de engenheiros de potência, visto que os métodos de continuação existentes na literatura sempre utilizam técnicas de parametrização complexas, e de interpretação puramente geométrica. Resultados obtidos com a nova metodologia para os sistemas testes do IEEE (14, 30, 57 e 118 barras) mostram que as características de convergência do método de fluxo de carga convencional são melhoradas na região do PMC. Além disso, durante o traçado das curvas PV, as diversas técnicas de parametrização podem ser comutadas entre si possibilitando o cálculo de todos os pontos da curva com um número reduzido de iterações. Diversos testes são realizados para proporcionar a comparação do desempenho dos esquemas de parametrização propostos.

The conventional load flow method is considered to be inadequate to obtain the maximum loading point (MLP) of power systems, due to the singularity of Jacobian matrix. Continuation methods are efficient tools for solving this kind of problem, since parameterizations techniques can be used to avoid such singularities. In this paper new options for the parameterization step are presented. It is shown that variables with clear physical meaning can be utilized to parameterize the power flow equations. The following variables have been tested: total real and reactive power losses, real and reactive power at the slack bus, reactive power at generator buses, and transmission line real and reactive power losses. The proposed parameterization schemes simplify the implementation of a continuation power flow, and make it easier for power engineers to understand its mathematical definition, since it uses physically meaningful parameters rather than purely mathematical and complex variables. Results obtained with the new parameterization techniques for the IEEE test systems (14, 30, 57 and 118 buses) show that the convergence characteristics of the conventional power flow method are improved at the MLP vicinity. In addition, it is shown that the proposed parameters can be switched during the tracing of the PV curve in order to efficiently determine all its points with few iterations. Several tests are carried out to compare the performance of the proposed parameterization schemes for the continuation load flow method.