Electrical Breakdown of Sulfur Hexafluoride at High Pressure

At Sandia National Laboratories, a 5.5 Megavolt Laser§Triggered Gas §Switch (LTGS) developed surface flashover within the§PMMA §envelope. This surface flashover occurs initially§during the regular §cascade switching process without affecting the§switch s electrical §performance. However, the switch will pre-fire in the§successive §shot. The damage to the envelope must be repaired§before normal §switch operation can resume. §A 340 kV system was designed which replicated§conditions found in §the LTGS. Besides measurement of flashover delay§times for various §dielectric materials (Lexan, Acrylic, etc.), emphasis§was put on §characterization of the flashover phenomenology. In§addition to §voltage and current diagnostics, fast optical imaging§of the flashover §along with the acquisition of optical emission§spectra (200 nm to §700 nm) was employed. §This book investigates the two events that occur§within the §chamber, surface flashover and volume breakdown.§Understanding §the fundamental physical mechanisms and the extent to§which these §processes influence discharge behavior is vital to§characterizing and §modeling electrical breakdown in high pressure SF6.