Non-destructive test methods for hollow-core composite insulators

Several test methods were evaluated in order to prove their suitability to detect voids, air bubbles, and adhesion failure in hollow-core composite insulators. Due to the relatively complex geometry of the insulators (bowed surface, shed-profile) and the criticality of even comparably small defects in high-voltage equipment, most of the methods did not provide satisfying results. Most promising seem to be Computed Tomography and a rather new method, the so-called Micro-Wave Based Detection.