Breakdown Characteristics of Compressed Dry Air and Its Application in GIS

Gas gap and surface discharge characteristics are important factors affecting the design of gas insulated electrical equipment. Compressed dry air(CDA) is one of eco-friendly gases to replace SF
6
gas in electrical equipment. This study reports the breakdown characteristics of dry air, SF
6
and 6%C
4
F
7
N/94%CO
2
gas mixture under AC voltages. It's found that the insulated strength of CDA at 0.8 MPa is comparable with SF
6
gas at 0.3MPa abs., and with 6%C
4
F
7
N/94%CO
2
gas mixture at 0.4MPa. CDA can be an alternative insulated gas in power equipment with larger size or higher gas pressure compared with traditional SF
6
insulated equipment. The lightning impulse breakdown strength of CDA is also obtained in a 550 kV GIS equipment. These results can provide a reference for the design of GIS equipment using CDA as an insulating medium and accelerate the promotion of environmentally friendly electrical equipment.