Partial Discharge Measurement for Early Fault Detection in Rotating Electrical Machines – Theory and Practical Experience

Abstract

This paper provides an overview of the physical fundamentals of partial discharges and typical PD sources in stator windings, including internal void discharges, surface discharges, slot discharges, and phase-to-phase discharges. The classical PD measurement circuit according to IEC 60270 and the evaluation of phase-resolved partial discharge (PRPD) patterns are briefly discussed. The core of the paper presents several industrial case studies on motors and turbo-generators in the voltage range from 10.5 kV to 22 kV, illustrating typical insulation defects and failure mechanisms.