Hydrophobicity distribution analysis of DC composite insulators

Hydrophobicity is an important operating performance indicator for composite insulators and the regularity of hydrophobicity distribution contributes to a more accurate evaluation to test results. In this paper, four DC composite insulators energized over a period of years in South China were selected for test and hydrophobicity tests were conducted by using static contact angle method. These tests included the hydrophobicity measurement with and without natural contamination and the hydrophobicity transfer with artificial contamination. Experimental results indicate that the high-voltage end and low-voltage end show clearly worse hydrophobicity and hydrophobicity transfer than the middle part. In other word, static contact angle, which characterizes the hydrophobicity and hydrophobicity transfer along the composite insulators are mostly inverted U-shaped and after the removal of natural contamination, the static contact angle significantly declined. Moreover, the roots of sheds show much better hydrophobicity transfer than the edges, especially for sheds with obvious fading phenomenon. According to the above hydrophobicity distribution, the results of hydrophobicity tests can better characterize the performance of composite insulators.