The Characteristics and Detection of the Partial Discharge Induced by the Micro Cracks in GIS Insulators

The micro cracks resulted from the defective manufacturing technology are common to see in GIS insulators, and many researches have already been done on it. However, most of these studies are based on the simulative defects made in laboratories, rather than on the defects on real made insulators, and thus the equivalence between the experimental condition and the practical situation in real substations cannot been guaranteed. In this paper, partial discharge (PD) experiments are carried out on a real made GIS post insulator with micro crack inside. It is found that the ultra-high frequency (UHF) method is not sensitive to the PD of this type based on the investigation on the PD characteristics, and the mechanism of the PD process is analyzed to explain why it cannot be detected by the UHF method. According to the special PD characteristics the defect displayed, suggestions on the adjustment of the PD frequency band is made in order to find the micro cracks in GIS insulators on-site.