Investigation of MIDEL 7131’s Dielectric Breakdown Strength and Thermal Behaviour : Master Thesis, an experimental study using concentric-like electrodes at elevated temperatures to study breakdowns

Abstract: Dielectric insulation are constantly exposed to various stresses, while also being expected to last for long periods of time. Naturally, they degrade with use and in demanding operational environments, this degradation phenomena can be accelerated, leading to costly consequences. With the constant evolution within the vehicle industry, high standards are established. For ignition coils, one of the challenges lies in achieving high performance, with the trade-off being a reduced insulation space. Furthermore, the operation of ignition coils at elevated temperatures could affect the insulation and its capabilities. Thus, it is important to investigate how the dielectric strength of an insulation behaves under these increased temperature conditions and constrained operational space, both in the short and long term. In this master thesis, the primary objective was to ascertain whether the oil would maintain its dielectric strength under prolonged elevated temperatures. The transformer liquid MIDEL 7131 was examined and assessed, through breakdown voltage tests from room temperature and up to temperatures of 140◦C. Subsequently analysing the results using descriptive statistics, employing both Gaussian and Weibull distributions. The observations from these measurements provide more data to the field of liquid dielectrics and allow a better understanding of how the condition and operating environment could affect the dielectric capabilities of transformer oils, with a specific focus on MIDEL 7131.