Analysis of Partial Discharges and Failure Mechanism in Electrical Machines with Hairpin Winding

The understanding of failure and aging mechanisms of electrical insulation systems will be essential in the future for the design of reliable electrical machines under increased requirements. Therefore, the repetitive partial discharge inception voltage (RPDIV) is selected in this paper to determine the condition of electrical insulation systems during accelerated aging. The change of RPDIV from unaged condition to failure is described, changes are analyzed and a theorem on the damage mechanism is developed. Then the failure locations are identified and indications of possible dominant thermal or electrical erosion processes and failure causes are discussed. Finally, a comparison is made between the service life of different test specimens representing the end winding on the one hand and the slot area of a real reference machine on the other hand.