Atlas tri-plate standoff insulators' design and test results

The Atlas system consists of 96 Marx generators, arranged in a circle. Sets of four generators feed a tri-plate transmission line, and the tri-plate lines in turn feed a central load region. The space between the plates is a nominal 2.00 cm (0.787 inch). This spacing and support of the central plate are provided by a set of insulators referred to as the tri-plate standoff insulators (TSI). The insulators were designed to provide the required mechanical support, ease of replacement or removal for maintenance, and the electric field gradient standoff. Two materials were selected: one was chosen because it has reasonable mechanical properties and a dielectric constant close to that of oil (polypropylene /spl epsiv/=2.3); the other material was selected because of its increased mechanical strength, even though the dielectric constant is higher than that of oil (Nylon MC 901 and 907 /spl epsiv/=3.7). Testing of the insulators was performed in a three-foot diameter tri-plate assembly. The test setup accepts four insulators at a time. The nominal operational voltage for the tri-plates is 240 kV at a t/sub eff/ of 0.87 /spl mu/s. The testing was performed at up to 450 kV with a t/sub eff/ of 2.8 /spl mu/s. The insulators were successfully tested until oil breakdown between the plates was reached, with no insulator flashover.