Study on aging of stator bar insulation of generator based on moment characteristics of partial discharge

In the present paper, the aging of stator bar insulation of generator is investigated based on the characteristics of partial discharge pulse distribution and statistical parameters, such as skewness and kurtosis. Although the changes of partial discharge distributive parameters and the statistical parameters mentioned above with aging time is not identical in different bars subjected to various stresses, a similar law is that the skewness of Hqn(φ) profile in all of specimens aged changes from positive into negative with aging time increasing. It is discussed the correlation of skewness with various type of defects in insulation. A new phenomenon is observed that the peaks of the Hn(φ) profile occur at 45° and 135° in bar insulation unaged, 0° and 180° in the bar insulation experienced moderate aging time., 90° and 270° in the bar insulation experienced longer aging duration, respectively. Although PD parameters mentioned above do not predict the lifetime of stator bar insulation of generator and evaluate insulation condition, they do give the useful information on defects in bar insulation with mica/epoxy