Introdução: O arco dentário superior de pacientes com mordida cruzada posterior normalmente apresenta-se atrésico e a expansão rápida da maxila é indicada para esses casos durante a dentadura mista promovendo abertura da sutura palatina mediana e incrementos transversais na região posterior e anterior do arco dentário. Objetivo: O objetivo deste trabalho consistiu em avaliar os efeitos da expansão rápida da maxila, utilizando o disjuntor com cobertura em acrílico, por meio do acompanhamento clínico nos incisivos superiores. Material e Método: A amostra do estudo foi composta por 21 indivíduos com mordida cruzada posterior, uni (2) ou bilaterais (21), e atresia do arco dentário superior. O procedimento de expansão rápida da maxila foi realizado na dentadura mista tardia, por meio do aparelho de expansão com cobertura oclusal em acrílico. Foram analisados os parâmetros clínicos obtidos mensalmente até o final do tratamento: o índice de placa dental visível (IPV), índice sangramento gengival (ISG), profundidade de sondagem (PS), nível clínico de inserção (NIC) e índice de sangramento á sondagem (SS). As medidas pré e pós-tratamento foram submetidas ao teste t pareado (p<0,05). Resultados: Não foram observadas diferenças estatisticamente significantes entre o tempo inicial e final para as variáveis ISG, ISS e PS, porém houve uma diminuição significativa para PV durante os períodos de 30, 60 e 150 dias e 180 dias. Conclusão: Alguns parâmetros clínicos periodontais (índice de profundidade á sondagem e índice de placa visível) diminuíram ou foram similares antes e depois do tratamento com ERM. Porém, o índice de sangramento á sondagem e o índice de sangramento gengival finais foram estatisticamente maiores que no início do tratamento / Introduction: The upper dental arch of patients with posterior crossbite is usually atresic and rapid maxillary expansion is indicated for these cases during the mixed dentition, promoting the opening of the medial palatine suture and transverse increments in the posterior and earlier region of the dental arch. Objective: The purpose of this study was to evaluate the effects of rapid maxillary expansion using the acrylic cover breaker, through clinical in the upper incisors. Material and Method: The study sample consisted of 21 individuals with posterior crossbite, uni (2) or bilateral (19) and upper dental arch atresia. The rapid maxillary expansion procedure was performed in the late mixed dentition using the expansion apparatus with acrylic occlusal cover. Were analyzed the clinical parameters obtained monthly until the end of the treatment: visible dental plaque index (VDP), gingival bleeding index (GB), probing depth (PD), clinical insertion level (CIL) and bleeding probing index SU). Pre-and posttreatment measurements were submitted to paired t-test (p<0.05). Results: There were no statistically significant differences between the initial and final time for GB, PD and SU, but there was a significant decrease for VDP during the 30, 60 and 150 day periods. Conclusion: Some periodontal clinical parameters (depth to depth index and visible plaque index) decreased or were similar before and after MRE treatment. However, the final bleeding index and gingival bleeding index were statistically higher than at the beginning of treatment

O presente trabalho visa o desenvolvimento de um sistema de monitoramento de disjuntor voltado a coletar informações para manutenção preditiva. São analisadas as características das variáveis que são monitoradas através de sensores ligados ao disjuntor, sua aquisição e o tratamento das informações. Um protótipo foi desenvolvido e instalado na subestação de Sumaré 440kV de ETEO (Empresa de Transmissão de Energia do Oeste Paulista). Um assunto importante para a manutenção é a avaliação dos tempos envolvidos na movimentação dos contatos principais do disjuntor principalmente na operação de abertura do curto circuito. Para tal é proposto um sistema não intrusivo que analise a oscilografia das tensões e correntes no disjuntor sincronizado com as correntes no circuito de disparo deste equipamento. A Transformada de Fourier aplicada no sinal de corrente/tensão sem perturbação permite determinar o valor do componente fundamental desse sinal. Com esse valor pode-se gerar uma senóide que superposta com o sinal coletado pelo oscilógrafo permite visualizar a alteração. A Transformada Wavelet é realizada através de filtros decompondo-se o sinal de corrente ou tensão em Análise Multiresolução, em diferentes estágios obtendo-se em cada, uma versão chamada aproximação (baixas freqüências) e uma de detalhes (altas freqüências), sendo assim, os distúrbios podem ser detectados e localizados no tempo em função do seu conteúdo de freqüência. / The present work addresses the development of a circuit breaker monitoring system so as to collect information for predictive maintenance. The characteristics of the variables that are monitored through certain sensors linked to the circuit breaker, its acquisition and the treatment of the information, are analyzed. A prototype was developed and installed at the 440kV Sumaré substation of ETEO (Empresa de Transmissão de Energia do Oeste Paulista) a Brazilian Transmission Company. An important aspect for the maintenance is the evaluation of the times involved in the movement of the circuit breaker main contacts, mainly at the opening operation for example during a short circuit. On this respect, a non-intrusive system that analyzes the oscillography of both voltages and currents in the circuit breaker synchronized with the currents in the tripping circuit of this equipment is proposed. The Fourier Transform applied to the current or voltage signal with no disturbance allows to determine the value of the fundamental component of this signal. With that value, it can be generated a pure sine wave which when overlapped to the signal collected by the oscillograph allows to visualize alterations. The Wavelet Transform is realized through filters and decomposing the current or voltage signal through the Multiresolution Analysis at different levels, in this way, obtaining in each level, a version called approximation (low frequencies) and another with details (high frequencies), thus, the disturbances can be detected and located in the time and as a function of its frequency content.

O presente trabalho visa o desenvolvimento de um sistema de monitoramento de disjuntor voltado a coletar informações para manutenção preditiva. São analisadas as características das variáveis que são monitoradas através de sensores ligados ao disjuntor, sua aquisição e o tratamento das informações. Um protótipo foi desenvolvido e instalado na subestação de Sumaré 440kV de ETEO (Empresa de Transmissão de Energia do Oeste Paulista). Um assunto importante para a manutenção é a avaliação dos tempos envolvidos na movimentação dos contatos principais do disjuntor principalmente na operação de abertura do curto circuito. Para tal é proposto um sistema não intrusivo que analise a oscilografia das tensões e correntes no disjuntor sincronizado com as correntes no circuito de disparo deste equipamento. A Transformada de Fourier aplicada no sinal de corrente/tensão sem perturbação permite determinar o valor do componente fundamental desse sinal. Com esse valor pode-se gerar uma senóide que superposta com o sinal coletado pelo oscilógrafo permite visualizar a alteração. A Transformada Wavelet é realizada através de filtros decompondo-se o sinal de corrente ou tensão em Análise Multiresolução, em diferentes estágios obtendo-se em cada, uma versão chamada aproximação (baixas freqüências) e uma de detalhes (altas freqüências), sendo assim, os distúrbios podem ser detectados e localizados no tempo em função do seu conteúdo de freqüência. / The present work addresses the development of a circuit breaker monitoring system so as to collect information for predictive maintenance. The characteristics of the variables that are monitored through certain sensors linked to the circuit breaker, its acquisition and the treatment of the information, are analyzed. A prototype was developed and installed at the 440kV Sumaré substation of ETEO (Empresa de Transmissão de Energia do Oeste Paulista) a Brazilian Transmission Company. An important aspect for the maintenance is the evaluation of the times involved in the movement of the circuit breaker main contacts, mainly at the opening operation for example during a short circuit. On this respect, a non-intrusive system that analyzes the oscillography of both voltages and currents in the circuit breaker synchronized with the currents in the tripping circuit of this equipment is proposed. The Fourier Transform applied to the current or voltage signal with no disturbance allows to determine the value of the fundamental component of this signal. With that value, it can be generated a pure sine wave which when overlapped to the signal collected by the oscillograph allows to visualize alterations. The Wavelet Transform is realized through filters and decomposing the current or voltage signal through the Multiresolution Analysis at different levels, in this way, obtaining in each level, a version called approximation (low frequencies) and another with details (high frequencies), thus, the disturbances can be detected and located in the time and as a function of its frequency content.

<p>The task for this Master thesis was to evaluate different black-box arc models for circuit-breakers with the purpose of finding criteria for the breaking ability. A black-box model is a model that requires no knowledge from the user of the underlying physical processes. Black-box arc models have been used in circuit-breaker development for many years. Arc voltages from tests made in the High Power Laboratory in Ludvika were used for validation, along with the resistance calculated at current zero, R0, and 500 ns before current zero, R500. </p><p>Three different arc models were evaluated: Cassie-Mayr, KEMA and an arc model based on power calculations. The third model gave very good results and if the model is developed further, the breaking ability could easily be estimated. </p><p>The arc model based on power calculations could be improved by using better approximations of the quantities in the model, and by representing the current better. A further suggestion for the following work is to combine the second arc model tested, the KEMA model, with the model based on power calculations in order to estimate the KEMA model parameters. </p><p>The R0 and R500 values should also be calculated from more tests, in order to find a clear limit of the breaking ability.</p>

Maintenance optimisation is essential to achieve cost-efficiency, availability and reliability of supply in electric power systems. The process of maintenance optimisation requires information about the costs of preventive and corrective maintenance, as well as the costs of failures borne by both electricity suppliers and customers. To calculate expected costs, information is needed about equipment reliability characteristics and the way in which maintenance affects equipment reliability. The aim of this Ph.D. work has been to develop equipment reliability models taking the effect of maintenance into account. The research has focussed on the interrelated areas of condition estimation, reliability modelling and maintenance modelling, which have been investigated in a number of case studies. In the area of condition estimation two methods to quantitatively estimate the condition of disconnector contacts have been developed, which utilise results from infrared thermography inspections and contact resistance measurements. The accuracy of these methods were investigated in two case studies. Reliability models have been developed and implemented for SF6 circuit-breakers, disconnector contacts and XLPE cables in three separate case studies. These models were formulated using both empirical and physical modelling approaches. To improve confidence in such models a Bayesian statistical method incorporating information from the equipment design process was also developed. This method was illustrated in a case study of SF6 circuit-breaker operating rods. Methods for quantifying the effect of maintenance on equipment condition and reliability have been investigated in case studies on disconnector contacts and SF6 circuit-breakers. The input required by these methods are condition measurements and historical failure and maintenance data, respectively. This research has demonstrated that the effect of maintenance on power system equipment may be quantified using available data. However, realising the full potential of these methods requires the gathering and utilisation of failure and maintenance data as well as condition measurements to be improved. / QC 20100823

The task for this Master thesis was to evaluate different black-box arc models for circuit-breakers with the purpose of finding criteria for the breaking ability. A black-box model is a model that requires no knowledge from the user of the underlying physical processes. Black-box arc models have been used in circuit-breaker development for many years. Arc voltages from tests made in the High Power Laboratory in Ludvika were used for validation, along with the resistance calculated at current zero, R0, and 500 ns before current zero, R500. Three different arc models were evaluated: Cassie-Mayr, KEMA and an arc model based on power calculations. The third model gave very good results and if the model is developed further, the breaking ability could easily be estimated. The arc model based on power calculations could be improved by using better approximations of the quantities in the model, and by representing the current better. A further suggestion for the following work is to combine the second arc model tested, the KEMA model, with the model based on power calculations in order to estimate the KEMA model parameters. The R0 and R500 values should also be calculated from more tests, in order to find a clear limit of the breaking ability.

Due to the rapid revolution in trading strategies, market environment is very different from the past, and the market intervention in national stock exchanges has been taken seriously again . However, very few studies discussed the rule-based trading suspension for individual stocks in the past, and most of them only focused on the impact of trading halt on market performance. For this reason, this study in addition to measures impact of market performance, another major analysis focuses on the differences between individual and institutional investors order behavior under different halt conditions. We try to understand whether the current halt mechanism achieves the purposes of reducing the information asymmetry and the abnormal volatility. The market performence empirical results show that transitory trading halt can reduce the overreaction of re-opening, but the halt of follow-up 5 minutes of the liquidity decreased, and volatility increased. Next, we find the individual investors order aggressive tend to be conservative in the period of suspension. In contrast, Institutional investor behavior will tend to be more positive with higher information asymmetry and will not be affected by the trading halt. Moreover, from follow-up 20 minutes individual-institutional transaction VWAP ratio, we find that the trading halt will improve the performance of individual investors transactions.

This thesis analyses the controlled switching methods applied to modern SF6 type circuit breakers for the purpose of reducing switching overvoltages. Main emphasis is placed on controlled switching methods applied at extra high voltage level, since the cost of failures caused by switching overvoltages is highest in this voltage level. After a brief introduction about circuit breakers in general, switching overvoltages and controlled switching methods are analysed. Also a case study about controlled switching of an unloaded overhead line is provided, and success of controlled switching method is evaluated.

Existing models describing the dynamic behavior of a six-pulse rectifier during a short-circuit fault condition are derived from switch models using time-domain average value parametric functions. Unlike these models, novel non-parametric dynamic models have been developed using analytical average-value modeling approach in this work. In this modeling approach, depending upon the number of switches conducting during a switching cycle, the operating point of the rectifier is brought into one of three modes of operation of a six-pulse rectifier. The model for each mode is represented by a differential equation. During output current calculation for the rectifier the operating model is selected based on firing angle and overlap angle functions derived in this paper. They completely characterize the dynamic behavior of current flowing through the dc inductor for a wide range of operating conditions with the exception of harmonics and asymmetrical currents which are dominant for faults occurring at the terminals of the rectifier upstream of the smoothing inductor. The results from the average value model and few other simple models have been applied for Thevenin ac source and synchronous generator supplied rectifier models to determine the characteristics of short circuit current from the rectifier. / text

Este trabalho apresenta resultados de testes com processo de usinagem para diferentes ferramentas de torneamento. Foram realizados ensaios para avaliar a diferença de comportamento quantoa esforçosde cortee acabamentosuperficialem operaçãode torneamento para um mesmo tipo de ferramenta, com variação na superfície de saída, sendo uma com quebra cavaco com outra de superfície de saída lisa. O material usinado foi aço ao carbono 1045 recozido, testado para duas diferentes velocidades, variando-se também a profundidade de corte e avanço para cada ensaio. Os testes foram executados em um torno mecânico convencional, onde as variáveis do processo foram coletadas com um sistema de aquisição de dados, através de um dinamômetro piezoelétrico para avaliação das forças de corte e um rugosímetro portátil para medida da rugas idade superficial. Observou-se nos resultados, uma forte diminuição dos esforços quando aplicada a ferramenta sinuosa com quebra-cavaco, bem como melhoria nas características do cavaco. Em relação à rugas idade superficial houve uma pequena melhora quando utilizada a ferramenta com superfície de saída lisa, situação decorrente das condições de remoção do cavaco. / This wark presents the results af machiningpracess tests with different turning tools. Tests were done to evaluate behaviors differenceson cutting efforts and surface finishing in turning operations to a same type of tool, with a variation on rake face, where one had a chipbreaker groove and the other are flat. The machining material was 1045 annealed carbon steel, tested to two different cutting speeds, changing also the depth of cut and the feed rate for each case. The tests were done in a conventionallathe, where the process variances were collected by a data acquisition system, through a piezoelectric dynamometer to evaluate the cut efforts and a portable rugosimeter to measure the surface roughness. The results show a strong reduction of the efforts when grooved tools with chip-breaker were applied as well an improvement on the chip characteristics. In relation to the surface roughness, it was observed a slight improvement when the tlat tool was used, because ofthe conditions of chip remova!.