Experimental test and modeling of hollow-core composite insulators

Hollow-core composite post insulators, used in high voltage electrical equipment, are important parts of the power substation systems. In many applications the composite insulators are considered as slender cantilever columns, fixed at one end and connecting to a conductor at the other end. During earthquakes the post insulators are damaged and sometimes fail near their base connection. When the post is pulled laterally, the tube dislocates from the walls in the end flange, and slips in and out the flange. Subsequently the composite tube sticks in the flange and slips again if the load is reversed, as it is occurring during earthquakes. In this study, an analytical model is developed using a combination of linear and nonlinear springs, viscous and frictional dampers and inertial masses. The developed macroscopic model is governed by a third-order differential equation which is derived in a state-space and solved by using Runge-Kutta integration in MATLAB. Several prototype insulators have been tested at the University at Buffalo's Structural Engineering and Earthquake Simulation Laboratory (SEESL). Through a methodical identification of the stiffness, mass, friction, and damping properties, the analytical model is verified to produce reliable estimates of strength, damping and global behavior.