Development process of micropores partial discharge of silicon rubber in prefabricated cable joint

To clarify the relationship between microporous defects and the development of partial discharge(PD) in silicone rubber, meanwhile evaluate insulation state of the prefabricated power cable joints quantitatively, the microporous defect is made based on real power cable joint, and PD signals are measured by step test method with the development of the defect. The discharge number, total energy and average energy of PD is gained to calculate the curves changed over time, based on which the breakdown process is divided into 4 stages, then phased spectra and grayscale maps are calculated for reflection of PD repetition rate and average energy in phase domain. Phase width, skewness of spectrum and coefficient of variation of parameter are employed to indicate the spectra statistical shape feature in each stage. The study indicates that the shape features of spectra are changed during the development of defect, the 3 features parameters are monotonously changed, and the changing rate is significantly higher at the end of the breakdown process. Evaluation method for micropores PD of silicon rubber is proposed based on the analysis of the parameters and the trend of PDs development.