Effect of water streams on the AC breakdown performance of short rod-plane air gaps

The ac breakdown performance of rod-plane air gaps in the presence of water streams has been explored. Experimental results show that the ac breakdown voltage of rodplane short air gaps in the presence of a water stream is significantly lower than in the dry condition. In addition, the ac breakdown voltage of an air gap decreases with the increase of the water stream velocity, diameter and conductivity. The relative breakdown voltage of an air gap decreases with an increase of water stream velocity from 0.75 m/s to 1.79 m/s and nozzle diameter from 1.0 mm to 3.0 mm by 2.6% / 0.1 m/s and 0.8% / 0.1 mm, respectively. High speed images of the deformation of the water stream and the breakdown process of air gap are reported show that with the increase of the applied voltage, the critical break-up length and the size of main water droplets decrease. In addition, the effect of the electrical field on the break-up length of a water stream and the size of droplets are independent of the jet velocity.