Voltage-time characteristics for steep-front impulse voltages of particle-contaminated spacers in SF6 gas-insulated switchgear

In this paper voltage-time characteristics of spacer surfaces for steep-front impulse waves are investigated under a particle-contaminated condition in SF6 gas. The characteristics are measured as a function of particle length, particle position and spacer shapes. Flashover voltages monotonically increase in the submicrosecond region as time to flashover is shorter, and are a minimum in the 1 μs region. Applicability of the equal voltage-time area criterion for estimating voltage-time characteristics is discussed and the technical meaning of the two parameters used in the estimation is clarified. Moreover, it is demonstrated that an optimized spacer with ribs remarkably improves flashover voltages in the submicrosecond region as well as in the 1 μs and power frequency region