Influence of contact contour on breakdown behaviors in vacuum under uniform field

We experimentally investigated influence of contact contour on breakdown characteristics in vacuum under uniform field. Four vacuum interrupters are used and their contact contours are designed to obtain effective area S_eff from 211 mm² to 550 mm². The contact parameters are contact diameter -42.76 mm, contact gap - 6 mm, contact thickness 16 mm and contact material -CuCr50. Basic impulse level (BIL) voltage (1.2times50 mus) voltage is applied. The experimental results show that 50% breakdown voltage U ₅₀ decrease 11% from 248 kV to 221 kV when effective area increase from 211 mm² to 550 mm². O n the other hand, the effective area S_eff has a significant influence on conditioning process. The larger the effective area, the slower the conditioning process.