On-Line Partial Discharge (PD) Detection in 420 kV Bushings, to Confirm Periodic, Off-line DGA, Increase System Reliability End-User Service Continuity

摘要

A Utility was confronting growing maintenance and outage risks related to a population of 420kV bushings of a certain vintage with high failure rates. The unexpected failures were resulting in extended loss of service to its customers and unplanned labor and maintenance expense. Periodic off-line testing of PF and capacitance did not always detect a failure condition. DGA sampling of the oil from some of the suspect bushings, did exhibit classic signatures for Partial Discharge of oil/paper insulation systems. An on-line electrical partial discharge (PD) detection and bushing monitoring system was installed on a 400kV, 1 25MVAR reactor. The work reported is shared here, and will show the correlation of increased DGA levels and the rate of On-Line Partial Discharge activity, in two of the three bushings on this reactor. This technique demonstrated that on-line Electric PD detection provides the early warning of incipient failure conditions inside the bushings, before increases in leakage currents, and of-line Power Factor and/or capacitance testing.