Pattern identification of surface flashover induced by discrete water droplets on polymer insulator

The formation of water droplets and the triggered surface discharge have been considered as one of essential stages during the flashover process of outdoor polymer insulators. In order to determine the discharge pattern induced by discrete water droplets, laboratory experiments were carried out in an artificial climate chamber to simulate different morphology of water droplets on polymer insulator. And then, pattern and characteristics of the induced surface discharges were identified to establish the relationship between the flashover performance and the droplet parameters, such as the contamination, volume and location. Obtained results reveal that with the development of surface discharges from initiation of corona discharge to surface flashover, the gray-scale histogram of discharge image shows the increasing number of discharge pixels at the side of higher gray-scale value, the total luminance emitted by surface discharges shows the significant increase at the stage of surface flashover. Compared with the little affection of droplet contamination, the location and volume of water droplets show the significant influence on the distribution and strength of surface flashover. Meanwhile, both entropy and box dimension of surface flashover can be obtained to indicate the effects of discrete droplet parameters on the irregular and complicated properties of surface flashover. Therefore, pattern identification of surface flashover induced by discrete water droplets is available to further investigation on flashover performance of polymer insulator.