Dielectric Testing of Composite Insulators

As the application of non-ceramic insulators is becoming more widespread, understanding their degradation and reliability gains ever higher importance. Diagnostics of the in-service insulators mainly rely on testing the condition of the surface. This includes visual inspection, inspection with various types of cameras (IR, UV, visible, etc.), or the evaluation of the hydrophobicity. However, as degradation can be related to the core and the shed-core surface, as well, it would be important to gain information about the inner layers. This paper presents a methodology allowing the dielectric testing of the insulator in a broad frequency range with different electrodes. Intact and degraded insulators are tested, and the paper presents the results.