Influence of sand/dust contamination on the breakdown of asymmetrical air gaps under lightning impulses

The authors review the important parameters of particles which are present in the environment when sand/dust storms occur. Basic features of the experimental system are summarized. Extensive measurements of breakdown voltages and times to breakdown are carried out under clean and polluted conditions using rod-plane and sphere-plane gaps. It is shown that when positive lightning impulse voltages are applied to asymmetrical gaps from 5 cm to 2 m, the presence of sand/dust contamination can cause a breakdown voltage reduction. However, the presence of particles can greatly affect the breakdown characteristics of rod-plane and sphere-plane gaps under negative lightning impulses. For gaps with moderately nonuniform field distributions, the particles can decrease V50 by ≤ 40%. If the field distribution is more nonuniform, the contamination can increase V50 by ≤ 50%. For highly nonuniform field gaps, V50 values for clean and contaminated gaps are approximately similar. Such effects are primarily caused by particles which settle on the cathode.IEEE, Institute of Electrical Engineers of Japa