Ageing extent assessment of large generator insulation using advanced characterization techniques

Ageing extent assessment of large generator insulation is of great significance for planning an effective outage and maintenance. In the past a few decades, the insulation condition of large generator was evaluated based on conventional dielectric parameters, which are found specific to some insulation system or testing condition, and so far are still controversial among researchers. In this paper, a set of advanced characterization parameters such as ultra-wideband frequency characteristics of PD, skewness of phase distribution of PD pulses, wavelet-transformed acoustic characteristics and ultrasonic wave propagation characteristics were proposed for ageing extent assessment of large generator insulation. Multistress ageing tests were performed and experimental results indicate that these advanced characterization techniques are prospective for ageing extent assessment and remaining lifetime estimation of large generator insulation