Title :
Assessment of insulation condition of generator stator bars based on velocity of ultrasonic waves
Author :
Hao, Yanpeng ; Xie, Hengkun ; Wang, Guoli ; Jia, Zhidong
Author_Institution :
State Key Lab. of Electr. Insulation for Power Equip., Xi´´an Jiaotong Univ., China
fDate :
6/1/2003 12:00:00 AM
Abstract :
The velocity of ultrasonic waves, which were launched using the pulse-echo method and propagated in a stator insulation, was measured to assess the insulation condition of the stator bars. A statistical minimum velocity (Vmin) and a statistical average velocity (Vav) were computed for a new and three sets of stator bars which were in operation for 16, 18 and 23 years. After velocity measurements, several conventional electrical parameters such as dissipation factor, capacitance, and partial discharge were measured, and microscopic examinations of dissected insulation of tested bars were examined with a scanning electron microscope and an optical microscope. Experimental results showed that Vmin and Vav decreased and more microscopic defects were formed in the insulation with increasing operating time of the stator bar. For the three sets of aged stator bars, the insulation conditions based on Ymin and Vav were consistent with those assessed by measuring electrical diagnostic parameters. Therefore, Ymin and Vav were used to assess the insulation condition of large generators. The measurement of ultrasonic waves may offer a broad prospect for stator insulation diagnosis.
Keywords :
capacitance; electric generators; insulation testing; machine insulation; optical microscopy; partial discharge measurement; scanning electron microscopy; stators; ultrasonic velocity measurement; ultrasonic waves; aged stator bars; capacitance; dissected insulation; dissipation factor; electrical parameters; generator stator bars; insulation condition assessment; insulation conditions; microscopic examinations; optical microscope; partial discharge measurement; pulse-echo method; scanning electron microscope; statistical average velocity; statistical minimum velocity; stator bars; stator insulation diagnosis; stator insulation propagation; ultrasonic waves measurement; ultrasonic waves velocity; Capacitance; Dielectrics and electrical insulation; Electric variables measurement; Optical microscopy; Partial discharges; Pulse measurements; Scanning electron microscopy; Stator bars; Ultrasonic variables measurement; Velocity measurement;
Journal_Title :
Dielectrics and Electrical Insulation, IEEE Transactions on
DOI :
10.1109/TDEI.2003.1207482