Dielectric flashover with triple point shielding in a coaxial geometry

Abstract

Increasing performance of vacuum insulator barriers is a common goal in pulsed power. Insulating performance is continually being improved while new methods are developed. Triple point shielding techniques have been shown to increase flashover voltage, but the role of cathode versus anode shielding is still not fully understood. Open circuit flashover characteristics were obtained for a coaxial geometry to view the effects of triple point shielding for this geometry. The tests included applying various combinations of triple point shields on zero and +45 degrees insulators. Shielding was tested at the cathode triple point outside of the dielectric and at the anode triple point inside the dielectric. The role of anode versus cathode triple point shielding was examined. Flashover voltage was observed to increase when either a cathode or anode triple point shield was applied; however, adding a shield to both regions lowered the flashover threshold. Both triple point regions were found to be important and dependent on each other for some coaxial geometries.

Effect of different coning angles on flashover characteristics across machinable ceramic in vacuum

“…Many researchers tried different methods to increase the surface flashover strength of vacuum insulators. These include the use of surface coatings to decrease the surface electrical resistivity and secondary electron emission (SEE), magnetic insulation [7], angled insulator geometry [89], and shielding the triple junction [10].…”