Caractérisation et modélisation du comportement diélectrique des systèmes d'isolation statorique des grandes machines tournantes lors d'essais PDT et RT

Abstract

Periodic maintenance testing of large generator and motor stator windings is generally conducted to assess the condition of groundwall insulation, identify maintenance needs and operating restrictions, and ultimately to guard against unexpected in-service failures [18]. Thus, non-destructive diagnostic tests are important tools to determine the condition of stator winding insulation. Our main interest will focus on implementation of two DC methods, in this case, the Ramp Test (RT) and the Polarization and Depolarization Test (PDT). These two methods have been the subject of several publications and special attention in the last decade [40]. In order to evaluate the performance of these two methods, laboratory and site tests were conducted on stator bars and a complete stator winding respectively of different manufacturers. For the measuring system, the RT/PDT prototype developed for the benefit of Hydro-Québec, is used and presented. In order to separate the contribution of leakage current from the measured total current, the modelization of the measured current is needed for analysis purpose. Hence, two models of the measured current will be presented. The first model is linear taking into account only the dielectric response of the straight part of the bar or the stator winding. The second model is nonlinear taking into account the dielectric response of the whole bar including the end winding parts. The determination of the unknown parameters of the modelling is performed using a numerical calculation through the Matlab software. This will allow us to avoid making some approximations and circumventing the difficulties encountered in the calculations. The nonlinear resistance and the Snaking effects observed during RT tests will also be presented and analyzed.

Date	27 Feb 2017
Original language	French
Awarding Institution	École de technologie supérieure
Supervisor	Éric David (Supervisor)