No abstract

Partial discharges can occur in different types of electric equipment and cause progressive insulation deterioration, so there is interest in monitoring partial discharges for assessing the state of the isolation of an electric system and to predict failures. Techniques to detect partial discharges, such as detecting ultrasonic emission, have been proposed in the literature, but as various effects can co-occur during a discharge, identifying characteristics in sound and pressure waveforms and correlating then with discharge characteristics is difficult. Simulations can assist in these correlations by allowing the isolation of the different phenomena. In this work the drift diffusion model, including photoionization, is coupled with the linearized compressible Navier-Stokes equations to simulate ultrasonic waves produced by partial discharges. Previous works have used the incompressible Navier-Stokes equations, so they can simulate ionic wind produced by the Trichel pulses, but no sound. In the literature, simulations have focused either on streamers or Trichel pulses. In this work both discharges and produced sound waves are successfully simulated for the needle-plane geometry in air. The electric current and charge per pulse are compared with experimental results reported in the literature for the same discharge conditions. The simulations have demonstrated that the sound waves depart from the electrode tip for the Trichel pulses, and for the streamers two sound waves are produced, one from the electrode tip and the other from the whole discharge length. Differences in the wave front with respect to the relative position to the electrode tip were analyzed, showing that near the discharge spot the sound wave is not a spherical wavefront. The sound wave for one of the discharges in the Trichel pulse regime was compared with experimental results in the literature. Results are in good agreement with the experimental data found in the literature. Both current and sound waves were successfully predicted and correlated with the discharge, results that can be used to help in the detection of partial discharges.

Este trabalho apresenta um sistema sensor para uso em laboratórios de ensino, composto por uma câmera USB e um software desenvolvido e disponibilizado pelos autores. O sistema sensor é adequado para o estudo de fenômenos associados à propriedade de polarização da luz, tendo sido testado em experimentos realizados para verificar a Lei de Malus e a eficiência espectral de polarizadores. São apresentados detalhes da montagem experimental, na qual a luz de uma lanterna de LED usada como fonte luminosa no visível é projetada numa tela branca após passar por dois polarizadores. A imagem projetada na tela é captada pela câmera e o software fornece a intensidade luminosa relativa da luz. Com o uso de dois polarizadores lineares tipo H rotatórios, ajustes lineares da Lei de Malus aos dados de intensidade da luz transmitida apresentaram coeficientes de correlação R maiores do que 0,9988. A eficiência dos polarizadores em diferentes regiões do espectro eletromagnético visível foi analisada com o auxílio de filtros de cor inseridos à montagem experimental. O sistema também foi empregado na avaliação da estabilidade temporal da intensidade do LED de luz branca.

This work shows the production steps of two optical fibre sensing setups which were specially designed for the activities of the 2018 Photonics Lab Open Day realized at the Federal University of Technology-Paraná in Brazil as a celebration of the first International Day of Light (16 May). The systems are based on the sensing properties of fibre Bragg gratings, a well-established photonic sensing technology but not covered in regular undergraduate Optics courses. The demonstrations of optical fibre sensing properties by means of funny scientific activities intended to stimulate high school and college students' interest in science, seeking greater engagement of these students in the research projects developed at the University. Fibre Bragg ability of detecting mechanical vibration and temperature changes was used to measure the temperature of the attendee's breath and vibrations produced during a short walk. Demonstrations were realized in a contest where students were challenged to walk smoothly over a flat surface instrumented with vibration sensors, as well as to blow into a tube containing the temperature sensor.Steps of the sensing systems implementation are provided in detail including aspects concerning to the choice of the apparatus design and the installation of the sensors.

This work shows the time behavior presented by the temperature, dilation and/or contraction strain and thickness of dual-cure dental resin cement measured by using optical techniques.