Hydrophobicity is one of most important properties for the pollution performance of composite insulators

and it is also one of important indexes to evaluate the operating state. Consequently

we presented the recommended test method and parameters of dynamic droplet test under AC voltage based on the round robin test of CIGRE D1.58 working group.By contrasting the results of the hydrophobicity tests for two materials such as silicone rubber and EVA resin

it can be concluded that the difference between the hydrophobicity of the two materials cannot be distinguished by the static contact angle method and the hydrophobicity classification method. At the same time

dynamic droplet test can effectively distinguish the two materials in the AC electric field. Hydrophobic characteristic life of HTV is 661.3 min

which is significantly higher than that of EVA resin. Furthermore

the dynamic process of the droplet on the surface of the insulating material and the process of the leakage current are divided into three stages: the hydrophobic retention stage

the hydrophobic degradation stage

and the hydrophobic loss stage. The electric field distortion caused by the droplet sliding along the surface of the material is the main reason of the loss of hydrophobicity. The dynamic droplet method has advantages in hydrophobicity tests and is expected to be a new method to evaluate the hydrophobicity of an outdoor insulation material.