Mechanical behavior of electrical hollow composite post insulators: Experimental and analytical study

Electrical post insulators are important components of electrical substations since any type of failure in such insulators leads to the breakdown of the local network. Although the electrical substations are often in service condition, any horizontal excitation due to the earthquake, or any extreme event, may cause lateral deformation and damage to the post insulators. Hollow composite post insulators, a new and evolving technology, have a very complex mechanical behavior due to their materials and connections. To date, the design of such post insulators has been based on the limited test results available in the literature. Most of experiments have been conducted on small-scale specimens focusing on the elastic response. This study presents a series of experiments conducted on a full-scale electrical hollow composite post insulator to investigate the static and dynamic mechanical behaviors, while a computational model is derived. The test series comprise, pull and cyclic quasi-static tests in addition to impact hammer tests, to assess the mechanical behavior of the insulators subjected to the lateral forces at different stages of damage. The key experimental results include the pre-peak force-displacement relationship, the cyclic response, the stiffness and strength deteriorations, and failure modes. The modal frequencies and the corresponding viscous damping ratios for the undamaged and damaged post insulator are calculated using the results of impact hammer tests. An analytical model is derived from the mechanical behavior to simulate the response of the un-damaged and damaged post insulator, and is verified by the test results.