Partial discharge measurements on the winding bars from a failed machine

Partial discharge (PD) measurement is an effective tool for the evaluation and monitoring of machine insulation condition. Assessment by PD measurement of the winding bars from a failed electric machine identified the cause of the failure and defined the condition of the insulation. The correlation of PD measurements on the machine prior to failure with the post-failure assessment shows where the PD started, the process and duration of the insulation deterioration, and the signature of the PD signals. The results of the assessment suggest what preventative action should have been taken for the machine. Additionally, this paper introduces new methods of PD measurement. Assessment of insulation by these methods provides an insight to the best choice of insulation in a new or refurbished machine, defines the insulation condition for cost effective preventative maintenance and minimises the cost of repair.