Effect of Magnetic Field on Partial Discharge Dynamics in Insulation Systems of Transportation Power Devices

Abstract

The globally observed trend toward electrically supplied devices is common in the transportation segment. Traditionally, the performance of electrical insulation has been assessed with respect to electric stresses and endurance. In all current-carrying devices, magnetic fields will also be superimposed on electric ones; therefore, the influence of a magnetic field’s exposure on partial discharge (PD) dynamics is an actual research topic. This problem is important in the transportation segment as well, where low- and medium-voltage levels are mostly used for supply and energy conversion (which are associated with high load currents). This article is focused on the influence of magnetic fields on the dynamics of PDs in the voids of insulation systems of transportation power devices and refers to both ac and dc cases. A rather weak magnetic field (80 mT) was established in order to detect and analyze early stages of PD behavior. The measurements of PDs that were carried out in a dedicated setup revealed their impact on PD intensity, which have been visualized in time-sequence diagrams and PD images. This detected effect is attributed to both the elongation of the charged particle trajectory and the enhancement of the electron energy due to acceleration. It has been shown that the impact of a magnetic field can be observed within a supply voltage frequency range of 20–400 Hz (which is typical for the transportation segment). The PD intensity was amplified in the above range at a magnetic field induction of 80 mT (even up to 50%). The effect of a magnetic field can be recognized as an additional modulation factor that influences the dynamics of PDs.