High voltage capacitors used in electricity distribution networks contain synthetic dielectric oils. These oils have a serious impact on the environment and new standards may prohibit their use. In this context, the company Condis wants to develop a dry high voltage capacitor whose electrical performances are equal to those obtained with a dielectric oil impregnated technology.
This thesis presents the development and the evaluation of two technologies for dry high voltage capacitors. The first technology uses prepreg composite materials and the second technology is based on the impregnation of a capacitor with thermoset resins. Spectroscopy measurements, partial discharges and dielectric breakdown tests were performed to evaluate the performances of these two technologies.
First, prepreg based capacitors were laminated from several commercially selected prepregs. The breakdown strenght of laminated capacitors is encouraging for a preliminary version although this technology presents many manufacturing challenges for producing a prototype.
Capacitive windings with different dielectric wall compositions were impregnated by VPI (Vacuum Pressure Impregnation) process with an epoxy resin and a silicone resin. Corona treatment of the polypropylene films proved to reduce significantly the level of partial discharges when compared to untreated films. Optical microscopic observations were made to identify the origin of the discharges in the dielectric wall. Larger scale capacitor prototypes were manufactured using the same process. These prototypes revealed cracks that were solved by adding a flexibilizer in the resin mixture.
Finally, a 2D finite element model was realized in order to study the influence of the configuration of the electrodes on the electrical field distribution. Simulations have shown that an offset electrode configuration results in a concentration of fields at the electrode edge 40% higher than the concentration observed in the case of aligned electrodes.
Prototypes manufactured by VPI process demonstrate good electrical performances although the level of partial discharges is high when compared to expected industrial standards.
| Date | 30 Aug 2019 |
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| Original language | French |
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| Awarding Institution | - École de technologie supérieure
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| Supervisor | Simon Joncas (Supervisor) & Éric David (Co-supervisor) |
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Poudret, R. (Author),
Joncas (Supervisor) &
David (Co-supervisor),
30 Aug 2019Student thesis: Master's thesis › Master in Engineering: Mechanical Engineering