Title :
Analysis of in-service aged stator bars
Author :
Morin, R. ; Novak, J.P. ; Bartnikas, R. ; Ross, R.
Author_Institution :
Inst. de Recherche d´´Hydro Quebec, Varennes, Que., Canada
fDate :
12/1/1995 12:00:00 AM
Abstract :
Stator bars subjected to operating stresses for 7 and 22 year periods were retrieved from a hydrogenerator to undergo short term electrical diagnostic tests in order to determine whether any significant aging of the insulation had taken place. The AC breakdown voltage (Ubk), partial discharge inception voltage (PDIV), the maximum charge (ΔQm) and total apparent charge (ΣjnΔQj) transfer of the partial discharges, tanδ and tanδ tip-up comprised the measured quantities statistically evaluated in the diagnostic test procedure. The AC breakdown voltage, PDIV and Δθm were found to exhibit a systematic trend with in-service time, thereby suggesting the occurrence of aging effects. That is, both the AC breakdown voltage and the PDIV were characterized by a decrease with time in-service, whilst the ΔQ m value exhibited an increase. However, no definite behavior was evinced by the (ΣjnΔQj), tanδ and tanδ tip-up values. The significance of the diagnostic test results is discussed in terms of Weibull statistics and the partial discharge behavior with time
Keywords :
Weibull distribution; ageing; charge exchange; hydroelectric generators; insulation testing; machine insulation; machine testing; partial discharges; stators; voltage measurement; 22 y; 7 y; AC breakdown voltage; Weibull statistics; hydrogenerator; in-service aged stator bars; insulation aging; maximum charge; operating stresses; partial discharge inception voltage; short term electrical diagnostic tests; tanδ tip-up value; tanδ value; total apparent charge transfer; Aging; Breakdown voltage; Charge measurement; Current measurement; Dielectrics and electrical insulation; Insulation testing; Partial discharge measurement; Partial discharges; Stator bars; Stress;
Journal_Title :
Energy Conversion, IEEE Transactions on
