In large high voltage rotating machines, the insulation system is continuously subjected to multiple stresses causing significant damage to its electrical properties and thereby reducing the duration of its useful life. The use of an anti-corona coating in the end-winding portion is one of the techniques used for the suppression of corona discharges and ensures a better protection of the equipment.
Epoxy/SiC composites are commonly used as resistive stress grading material for high voltage applications, such as for the corona protection of the end-winding of the stator windings of large rotating machines. Depending on the grain size, concentration and composition of materials, a wide range of electrical parameters can be reached for epoxy/SiC composites. In this document, the optimum values of the electrical characteristics of the stress grading material (yielding the lowest value of the maximum electrical field) were calculated numerically for a given geometry, and it was found that the optimum values lay in the range accessible by SiC technology. Another modeling method (FEM) was used to model the same geometry in order to validate the results obtained by the analytical method.
Since temperature is an important factor in the design of such systems, measurements were carried out under different temperatures in order to evaluate the behavior of the anti-corona coating in the presence of heat stresses; it was shown that the increase of temperature decreases the electric resistivity of epoxy/SiC composites but the electrical field developed at the exit from slot did not present a potential risk of partial discharges in this region.
| Date | 4 Mar 2016 |
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| Original language | French |
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| Awarding Institution | - École de technologie supérieure
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| Supervisor | Éric David (Supervisor) & Issouf Fofana (Co-supervisor) |
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Merouchi, A. (Author),
David (Supervisor) & Fofana (Co-supervisor),
4 Mar 2016Student thesis: Master's thesis › Master in Engineering: Electrical Engineering