Submitted by Lucienne Costa (lucienneferreira@ufcg.edu.br) on 2018-04-24T16:40:39Z No. of bitstreams: 1 BRUNO ALBUQUERQUE DIAS – DISSERTAÇÃO (PPGEE) 2017.pdf: 3277136 bytes, checksum: 1277dbc3bda9c5d90497f95d8bf94878 (MD5) / Made available in DSpace on 2018-04-24T16:40:39Z (GMT). No. of bitstreams: 1 BRUNO ALBUQUERQUE DIAS – DISSERTAÇÃO (PPGEE) 2017.pdf: 3277136 bytes, checksum: 1277dbc3bda9c5d90497f95d8bf94878 (MD5) Previous issue date: 2017-03-17 / CNPq / O acúmulo de poluentes na superfície dos isoladores, que compõem as linhas de transmissão, permite a formação de uma camada de substâncias que, sob incidência de névoa, chuva ou orvalho, produzem soluções condutoras. Na região norte do Brasil, muitos casos de poluição biológica são caracterizados como limo, associação de microalgas e fungos, a resistência dielétrica da superfície do isolador, nestes casos, é reduzida, causando falhas no sistema elétrico. Para investigar o efeito dessa poluição sobre os isoladores, o presente trabalho apresenta um modelo computacional que relaciona o aspecto visual do limo no isolador (intensidade, forma e local) com a sua corrente de fuga obtida por simulação e correlaciona eficiência da simulação com experimentos em laboratório. Os objetos de teste utilizados foram isoladores de disco de vidro, limpos e poluídos com limo. Os isoladores contaminados foram retirados da subestação de Guamá, Pará, Brasil e os experimentos realizados no Laboratório de Alta Tensão da Universidade Federal de Campina Grande, na Paraíba. As simulações computacionais utilizam o Método dos Elementos Finitos e, assim como as medições laboratoriais, foram realizadas para diferentes condições de umidade, uma vez que essa variável tem influência significativa na condutividade do limo. A simulação se mostrou eficiente e os resultados apresentados mostram que é possível estimar a corrente de fuga desse tipo de isolador sob diferentes condições de umidade e diferentes níveis de poluição. / The accumulation of pollutants on surface of insulators allows the formation of a layer of substances that, with mist, rain or dew, produces conductive solutions. The surface dielectric strength, in these cases, is reduced, causing failures in electrical system. In the northern region of Brazil, many cases of biological pollution are characterized as slimes, association of microalgae and fungi. To investigate the effect of this pollution on the insulators, the present work presents a computational model that relates the visual aspect of slime in the insulator (intensity, shape and location) with its leakage current obtained by simulation and correlates efficiency of the simulation with laboratory experiments. Test objects used were glass disk insulators, cleaned and polluted with slime. The contaminated insulators were removed from the Guamá Substation, Pará, Brazil and the tests performed at the High Voltage Laboratory of Federal University of Campina Grande in Paraíba, Brazil. Computational simulations using Finite Element Method and, as well as the laboratory measurements, were performed for different humidity conditions since this variable has a significant influence on slime conductivity. The simulation proved to be efficient and the presented results show that it is possible to estimate leakage current of this type of insulator under different humidity conditions and different levels of pollution.

Cette thèse s’inscrit dans le cadre de l’amélioration du comportement électrique des isolateurs de lignes haute tension ; l’objectif est d’assurer une meilleure fiabilité et qualité d’alimentation en énergie électrique. Ce travail a été motivé par la nécessité de répondre à trois questions liées au comportement des isolateurs verre en zone polluée. La première porte sur la recherche d’une méthode permettant de calculer la tension de contournement des chaînes polluées selon le type d’isolateur et ses caractéristiques. La deuxième question concerne la différence de comportement entre les isolateurs en verre et les isolateurs en porcelaine de type « outerrib » ; ce type d’isolateurs présente une forme spécifique adaptée aux environnements à forte pollution. Les tensions de contournement ainsi que les trajectoires de l’arc sur les isolateurs en verre sont très différentes de celles observées avec les isolateurs en porcelaine. Et la troisième question est relative à la défaillance des isolateurs recouverts de silicone lors des essais en chocs (des impulsions de tension) à front raide. En effet, les isolateurs recouverts d’une couche de 0.3 mm (ou plus) de silicone hydrophobe explosent lorsqu’ils sont soumis à des impulsions de tension à front raide d’amplitude très élevée pendant un temps très court. Différents mécanismes pouvant être à l’origine de l’explosion/éclatement des isolateurs recouverts d’une couche de silicone sont discutés. Il ressort des différents tests et analyses que le mécanisme le plus probable semble être la fragmentation par plasma. En effet, suite à l’application d’une tension à front raide, d’amplitude très élevée, des canaux (fissures) microscopiques prennent naissance là où le champ électrique est le plus intense. L’application répétitive des chocs de tension conduit au développement de décharges dans ces canaux (rupture diélectrique de l’air) c’est-à-dire des arcs (canaux de plasma) qui se développent/propagent dans le volume de l’isolateur. La puissance déchargée (c’est-à-dire l’énergie stockée dans les condensateurs du générateur en des temps très courts) dans ces canaux à chaque choc étant très élevée, elle conduit à l’explosion de l’isolateur après quelques chocs (parfois 5 ou 6 suffisent): c’est la fragmentation par plasma. / This thesis deals with the improvement of the electrical behavior of insulators of high voltage lines; the objective is to ensure better reliability and quality of power supply. This work was motivated by the need to answer three questions related to the behavior of glass insulators in polluted areas. The first one concerns the search for method for calculating the flashover voltage of polluted chains according to the type of insulator and its characteristics. The second question concerns the difference in behavior between glass insulators and "outerrib" porcelain insulators; this type of insulator has a specific shape adapted to environments with high pollution. The flashover voltages as well as the trajectories of the arc on glass insulators are very different from those observed with porcelain insulators. And the third issue is the failure of silicon-coated insulators during shock tests (pulses) with a steep front. Indeed, insulators coated with a layer of 0.3 mm (or more) of hydrophobic silicone explode when subjected to very high amplitude steep-edge voltage pulses for a very short time. Different mechanisms that may be responsible for the explosion / puncturing of insulators covered with a layer of silicone are discussed. It appears from the various tests and analyzes that the most probable mechanism seems to be plasma fragmentation (cracking). Indeed, following the application of a steep front voltage, of very high amplitude, microscopic channels (fissures) originate where the electric field is most intense. The repetitive application of impulse voltages (shocks) leads to the development of discharges in these channels (breakdown of the air), i.e.; arcs (plasma channels) which develop / propagate in the volume of the insulator. The discharged power (i.e.; the energy stored in the capacitors of the generator in a very short times) in these channels (cracks) at each shock being very high, leads to the explosion of the insulator after some shocks (5 to 6 sometimes): it is the fragmentation by plasma or plasma cracking.