Magnetic Field Effects on Partial Discharges in Electrical Insulation Subjected to PWM Excitation

This article depicts an original measurement methodology and detection approach for determining the influence of a magnetic field on partial discharge (PD) dynamics in electrical insulation while subjected to pulsewidth modulated (PWM) excitation. Unlike conventional PD measurements that are only carried out in an electric field, it was demonstrated that the interplay of electric and magnetic fields enhances a PD's intensity. The quantitative effect of a magnetic field was captured by phase-resolved acquisition and visualization on time-sequence intensity diagrams. The increase in the PWM carrier frequency resulted in enhanced intensity and was also elevated by the effect of the magnetic field. The influence of the magnetic field on the PDs was associated with the elongation of the charged particle trajectory and effects that were caused by the Lorentz force. The presented study may contribute to PD measurement methodology in the power electronic environment in both electric and magnetic fields as well as a better understanding of the underlying physical mechanisms. Since the endurance and reliability of electrical insulation that is subjected to fast switching, PWM-modulated power electronic-based excitation is an actual topic in many segments, such as power grids, industry, and transportation; the awareness of PD-intensity modulation that originates from the presence of a magnetic field should be raised and investigated.