Assessment of Finite Element Simulation Methodologies for the Use of Paschen’s Law in the Prediction of Partial Discharge Risk in Electrical Windings

Abstract

The prediction of partial discharge (PD) occurrence in electrical motors at the design phase is key to the development of future devices. As a result, there is a growing interest for predictive numerical tools to help assess partial discharge risk. Currently, most efforts rely on Paschen's law as a criterion for partial discharge occurrence between two neighboring wires. Its use requires field lines data obtained with finite element electrostatic simulations. In this paper, we explore the extent to which these finite element simulations can be simplified without losing accuracy regarding subsequent partial discharge risk assessment using Paschen's law. First, we examine whether partial discharge risk predictions between two turns are influenced by the presence of other turns nearby. Our results suggest that the partial discharge is mostly a local phenomenon hardly affected by the surroundings. Performing simulations for an isolated pair of conductors may thus be sufficient to determine the maximum allowable constraints between two turns, at least for large wires. Also, we show that neglecting field line curvature in the calculation does not alter predictions, vindicating the straight line assumption which has been adopted in the literature for the sake of simplicity.

Keywords

• Partial discharges
• electric motors
• finite element analysis
• insulation testing