Influences of Electric-Field Distribution Along the String on the Aging of Composite Insulators

This paper studies the uneven aging of the composite insulators along the string caused by the nonuniform electric-field distribution. Sheds along the string of two 110-kV composite insulators with varied operation time on transmission lines are analyzed systematically by means of hydrophobicity and thermally stimulated current (TSC) tests, and the aging characteristics of different part of the axial sheds are compared. This paper studies the influences of the electric-field distribution along the string on the aging of composite insulators, combined with the results of electric-field simulation and electric aging tests. Results show that the higher the electric-field strength is, the worse the hydrophobicity of composite insulators surface is and the larger the amount of trap charge is. The study suggests the nonuniform electric-field distribution is the main reason for the uneven aging of the sheds along the composite insulators string.