Study on aging characteristics of generator stator insulation based on dynamic mechanical analysis and ultrasonic wave method

Accelerated multifactor aging tests in laboratory have been conducted on stator insulation of large generator (18 kV, 300 MW) to identify useful diagnostic parameters for insulation aging characteristics. Dynamic mechanical parameters and ultrasonic wave velocity are measured for stator insulation of different aging time. The experimental results show that the apparent activation energy of glass transition (AAEGT) increases, while the storage modulus and dynamic viscosity of insulation decrease greatly with aging time, and the ultrasonic wave velocity propagated in stator also decreases obviously. Ultrasonic wave velocity can be used to describe the aging characteristics of stator insulation. The results also examined the adhesive properties decreasing of insulation interface results in the dielectric properties decreasing of insulation.