| Title |
SLI, AC Breakdown Voltage Characteristics of SF_6/CF_4 Mixtures Gas in Nonuniform Field |
| Authors |
황청호(Hwang, Cheong-Ho) ; 성허경(Sung, Heo-Gyung) ; 허창수(Huh, Chang-Su) |
| Keywords |
Breakdown ; AC Voltage ; standard lightning impulse voltage ; SF_6 ; CF_4 |
| Abstract |
Although many studies have been carried out about binary gas mixtures with SF_6, few studies were presented about breakdown characteristics of SF_6/CF_4 mixtures. At present study the breakdown characteristics of SF_6/CF_4 mixtures in non-uniform field was performed. The experiments were carried out under AC voltage and standard lightning impulse(SLI) voltage. Breakdown characteristics were investigated for SF_6/CF_4 mixtures when AC voltages and standard lighting impulse voltage was applied in a needle-plane. The needle-plane electrode whose gap distance was 3 mm were used in a test chamber. SF_6/CF_4 mixtures contained from 0 to 100% SF_6 and the experimental gas pressure ranged from 0.1 to 0.5 MPa. The breakdown characteristics of SF_6/CF_4 mixtures in non-uniform field may be influenced by defects like needle-shaped protrusions. In case of slowly rising SLI voltage and AC voltage it is enhanced by corona-stabilization. This phenomena caused by the ion drift during streamer development and the resulting space-charge is investigated. In non-uniform field under negative SLI voltage the breakdown voltage was increase linearly but under positive SLI voltage the breakdown voltage increase non-linearly. The breakdown voltage in needle-plane electrode displayed N shape characteristics for increasing the content of SF_6 at AC voltage. SF_6/CF_4 mixture has good dielectric strength and arc-extinguishing properties than pure SF6. This paper presents experimental results on breakdown characteristics for various mixtures of SF_6/CF_4 at practical pressures. We could make an environment friendly gas insulation material with maintaining dielectric strength by combing SF_6 and CF_4 which generates a lower lever of the global warming effect. |