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PhD Thesis Defense R. Acheen – Determination & influence of the existence of partial discharges in a railway traction system using SiC-based components

Event information

Start date :09/11/2020

End date :09/11/2020

Time :10:00

Location : to be confirmed, 31000, Toulouse

PhD Thesis Title: « Determination and influence of the existence of partial discharges in a railway traction system using SiC-based components »
By Robin Acheen

Doctoral School: GEET

Thesis of Toulouse III – Paul Sabatier University, prepared at LAPLACE and LSEE laboratories, and IRT Saint Exupéry.

Summary

Nowadays, electrical energy is used in many applications such as railway, aeronautic or automotive sectors, to mention only transportation for example. The rationalization of this energy is a major axis of development in the current context of “More Electrical”. Therefore, the reliability of the electrical systems and especially of the Electrical Insulation Systems (EIS) is crucial data to ensure that the electrical equipment operates accurately during its complete life cycle. Supply systems and subsystems undergo increasingly severe electrical stresses. Problematics and operating environment may change, but there is a single common goal: reliability must be assured and ageing must be anticipated and controlled to the largest extent possible.

 

In this context, the introduction of SiC-based components in the electromechanical chain presents numerous advantages, but has consequences on the reliability of the insulation systems in the machine. For switching frequencies up to 5 kHz, and dV/dt varying from 15 to 30 kV/µs, a system lifetime of around 40 years (or 200 000 hours) must be guaranteed. The question that arises is to know what margin insulation systems of the current equipment have. It is thus necessary to determine whether, under normal operating conditions, phenomena that did not previously exist or were not completely apprehended will appear with the transition to SiC-based inverters. One of these phenomena is Partial Discharge (PD) and its development in machines, and more precisely in the turn-to-turn, turn-to-ground, and phase-to-phase insulation systems.

Therefore, the objective of the thesis is to study the influence of the electrical stress imposed by inverters using SiC-based components on the insulation of machines, in particular its impact on PD activity and, in the longer term, on ageing. To do so, in a first phase, and after a short debugging study on a real system, the conditions for the inception of PDs in the chain are systematically determined depending on both geometrical and electrical parameters. The results are then compared to those obtained with a chain having inverters using SiC-based components. In a second phase, the influence of those constraints in terms of PDs and ageing is evaluated on very basic samples. These constraints are finally reproduced in a third and final phase on more complex samples representative of the real machine, which are thus subject to accelerated aging, all with the aim of establishing aging laws, as well as studying the degradation of the insulation systems under the effect of the applied stresses.