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.