Application of On-Line Partial Discharge Measurement on Rotating Electrical Machines

Abstract

Partial discharge (PD) is a localized dielectric breakdown of a small portion of a solid or uid electrical insulation system under high voltage stress, which does not bridge the space between two conductors. Partial discharges occur as symptoms of a number of failure mechanisms related to motors, generators and switchgear. As a re- sult, partial discharge testing may be used as a predictive maintenance tool. For high voltage equipment, the integrity of the insulation can be con rmed by monitoring the PD activities that occur through the equipment's life. To ensure supply reliability and long-term operational sustainability, PD in high-voltage electrical equipment should be monitored closely with early warning signals for inspection and maintenance. PD can be tested by on-line or o ine methods. For o ine PD testing, equipment has to be disconnected from service which is not suitable for some applications. So Online PD measurement is preferred for such cases. In this project on-line partial discharge testing is carried out on various HT ro- tating electrical machines. This is to nd the level of deterioration in the stator insulation of the machine and to quantify the level of discharge in pC. The mea- surements, as done by PD measurement system, are veri ed with lab results. This is to ensure the suitability of application of On-line PD measurement on rotating machines. Noise causes major problem in the analysis of PD signals as they mask the original signals. So proper noise rejection technique should be used. Here various noise rejection techniques are studied and wavelet transformation technique is used for noise rejection. The results are examined and it is found that WT technique pro- vides a robust methods for noise rejection in on-site applications where severe noise is present.