AC breakdown and decomposition products detection characteristics of eco-friendly insulating medium in gas insulated...

Gas Insulated Switchgear (GIS) was a crucial electrical equipment that provides the safety and security of power systems, and finding the eco-friendly alternatives of sulphur hexafluoride (SF6) as insulating medium in GIS has been an urgent demand in past decades. However, few studies reported the specific dielectric strength under various electrodes and partial discharge (PD) decomposition products detection of applying the eco-friendly gas in GIS. In this paper, the insulation properties among C₄F₇N/CO₂ mixtures, dry air and CO₂ were explored under the reduced-scale gas-insulated experimental device. The relationship between AC breakdown voltage and gas pressure was gained under the different electrodes and gap distances, and 0.6 MPa 7% C₄F₇N/93% CO₂, 0.9 MPa dry air, 0.9 MPa CO₂ all possess the capacity to be the insulating medium in eco-friendly gas insulated switchgear. Furthermore, the partial discharge experimental was also carried out to realize the decomposition products detection of dry air, which designs three common defect types including metal protrusion defects, air gap defects, and metal contamination defects. The decomposition products detection result shows that the contains of CO₂, CO, and NO₂ linearly increase with the increasing applied voltages and times, and the partial discharge defects are distinguished according to the ratios of c(CO₂ + CO)/c(NO₂) and c(CO₂)/c(CO). The results can provide the basis for the further development of eco-friendly gas insulated switchgear.