For fog type disc suspension porcelain insulator, is used un-synchronism soggy of inner shed and inhibition of discharge by high groove edge under shed, so the artificial pollution flashover voltage is higher, and the anti-pollution performance is better. This type is suit for industrial dust, chemical industry, and salt coastal and foggy area.
  At the bottom of fog type disc suspension porcelain insulators, there is deep edge groove, and the inner interspace under the shed is not easy to be affected with damp. But if the inner interspace is fully damp, the surface of top shed has been already over-damp, this would be affected the pollution washing off, so as to improve anti-pollution withstand voltage, this is why this type required the big creepage distance.