Evaluation of Hollow Core Composite Insulators

This paper presents preliminary results and analysis of a cantilever load test on two types hollow-core composite insulators and summarizes the response of the insulators to different types of loading. The tube of the insulator is a cylindrical shell of fibers-glass in a resin-based matrix with aluminum flange end fittings. The integrity of the tube-flange connection is checked for leaks, slip, damage, and bond degradation. Tests indicate that he actual cantilever load causing failure was much higher than the rated SML provided by the manufacturers. While there were occasionally sounds indicating that something was going on in the insulator prior to catastrophic failure, there was no change in the force deflection curve of the test. While there were slight changes in the damping and frequency of the insulators as the loading increased, the changes were small and did not indicate degradation of the insulator. Two failure modes were observed: failure of the lower flange and shear failure at the tube-flange connection. In one case the shear failure was in the bond to the flange and in the other it was in the tube adjacent to the bonding material. In the unbonded tube, there was clear friction damping. In bonded tubes, the presence of friction damping needs further investigation.