Characteristics of ultra-wideband partial discharge of insulation in aging process

The characteristics of partial discharge (PD) in aging process of insulation are studied in ultra-wideband range from 0 to 500MHz in this paper. The electrical or thermal aging of epoxy samples involving cavities with cone-cone electrode or needle-plate electrode systems are conducted. A TE571 PD detector is used to distinguish the discharge classification, and an ultra-wideband PD detecting system is employed for detecting ultra-wideband PD characteristics of insulation in aging process. The experimental results show that the major characteristic peaks of these insulation samples locate in the frequency ranges of such as 0 approx. 75MHz, 150 approx. 200MHz. In addition, the discharge characteristics of stator bar insulation samples of 300MW turbo-generator out of service is also measured, indicating that characteristic peaks locate in the frequency range of 100 approx. 125MHz.