Estudo do trilhamento de núcleo em isoladores poliméricos.

Abstract

In the electric energy facilities, the isolation systems play an important hole, reducing the losses and providing the high voltage transmission. The equipment that provides the isolation in electrical systems is the insulators. When an insulator fails, it can cause the transmission line outage, interrupting the supply of electric energy and severely injuring the concessionaire with the fines imposed by regulating agencies. Historically, the insulation systems in transmission lines have been represented by ceramic insulators, which use glass or porcelain. However, in recent years, a particular class of insulators, composed by organic materials, has detached: the polymeric insulators. As all equipment in an electric system, the polymeric insulators demand efficient monitoring techniques and deep study of its degradation factors. Core tracking is a cause of polymeric insulators failure. Aiming to understand the core tracking and its formation process, a laboratorial technique of core tracking creation is proposed. Moreover, an investigation of physical evidences of core tracking has been carried out. An ultraviolet camera and a termovisor have been used to inspect the levels of corona discharges in the insulator’s neighborhoods and the temperatures on the insulator’s surface. It was observed that corona rings have influence in thermal gradients and corona discharges patterns. Influence of corona rings in the levels of corona discharges and insulator’s temperature has been evaluated. Moreover, the electric field distribution and electric potential conditions of these corona rings have been computationally simulated, using the Finite Elements Method. The simulations allowed the graphical representation of electric field and potential, and a better understanding of the phenomena. Finally, aiming to extend the insulator’s useful life, an optimized corona ring, designed for 230 kV class polymeric insulators was projected, constructed and evaluated. The results of the experiments with the laboratorial technique of core tracking creation indicates that humidity is an important factor in the core tracking formation process, speeding up it. The results of the corona rings experiments demonstrate that under-dimensioned corona rings can be harmful to the polymeric insulators. On the other hand, over imensioned corona rings do not offer the ideal performance. From the computational simulations and lab tests, it is possible to conclude that the projected and constructed corona ring is a viable and functional alternative for 230 kV class insulators. It can also be conclude that, in corona ring projects, it is necessary to take in account the installation place, the degree of pollution and the climate to which the insulator will be exposed.