Analysis of the intrinsic characteristics of the partial discharge induced by typical defects in GIS

Partial discharge (PD) monitoring plays an important role in the maintenance of the high voltage (HV) apparatus, such as transformer and gas-insulated substation (GIS). In recent years, the ultra high frequency (UHF) method for PD detection arouses great interest of many researchers because of its high sensitivity and anti-interference capability. The coupling of UHF signal and process of the signal constitute the UHF detection method. There are three key components for the coupling of UHF signal in GIS, including the frequency spectrum characteristics of the PD source, the propagation characteristics in GIS, the coupling style and the capability of the UHF coupler. Many researchers are interested in the recognition algorithm and the analysis procedure of the PD data. But the intrinsic attributes of the partial discharges should attract more attentions because they are the foundation of the UHF detection method. This paper focuses on the intrinsic characteristics of the typical defects in GIS, such as the amplitude of the time-domain signal and frequency spectrum characteristics. Four types of typical partial discharge sources are designed and fabricated, including floating metal, protrusions, particle on the spacer, and void in solid insulation. Several different structure sizes of each defect are applied to ensure the consistency of the results and discover the factors that affect the frequency spectrum characteristics. The results of the study present the essential characteristics of the partial discharge. It can be applied to the design of the coupler and amplifier circuit. In addition, the sensitivity and anti-interference capability of the UHF method are promoted effectively, and it is valuable for calibrating the intensity of PD in GIS.