Finite Element Analysis of DC Partial Discharges in Failure Types of Thin Insulation Layers in Traction Battery Systems

Improving insulation testing in traction battery systems is crucial for quality standards and the safety of passengers in electric vehicles. The DC phase resolved partial discharge diagnostics is sensible and enables information about the cause of insulation faults. Faults are referred to PRPD patterns using a DC test voltage with a superimposed AC voltage ripple as a phase reference. These patterns vary depending on the start electron location. Thus, derived models are created by analyzing defect geometries in microsections. Electric field distribution and PD activity are calculated using a time domain finite element method in combination with a stochastic tree model. The electric field distribution is mainly influenced by interfacial polarization at the surface of solid impurities. The voltage ramp and the superimposed ripple of the dc test voltage can cause partial discharges in the volume of the defect. The information about PD locations and the type of geometry of the defect can be obtained from the shape of the PD patterns. Thus, the paper results expand the knowledge about DC phase resolved partial discharge diagnostics and improve the root cause analysis of insulation faults in traction battery systems.