Under nanosecond pulsed coaxial electric field, surface flashover voltage over the interfaces between nylon 1010 and transformer oil increases almost linearly with gap length, and the steeper rising edge of applied pulse, the higher flash-over voltage. Surface flashover properties are closely related to the electric field at the triple junctions of solid-liquid-electrode and the field gradient along the interfaces. Although the increased difference between inner and outer electrode radii will enhance electric field strength at the triple junctions and nonuniformity degree of potential distribution along interfaces, it reduces simultaneously terribly the surface field strength of coaxial inner electrode, so that flashover voltage doesn’t descend, but ascends almost linearly with gap length. The average flashover strength in coaxial electric field can be estimated by that in uniform electric field for large enough difference between inner and outer electrode radii, which is useful to practical engineering design for coaxial pulsed power apparatuses.
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