The Response of Substation Bus Systems to Short Circuit Conditions, Part II: Measurements on the Transverse Vibration of Selected Station Post and Pin-Cap Insulators

The first three natural frequencies of selected, 230 and 115 KV, cantilever-mounted insulators were measured using a frequency scanning procedure. The values of these frequencies indicate that the behavior of the insulators under fault load conditions may usually be described by a mathematical model having distributed mass and elasticity, the Euler-Bernoulli equation. The values of the first and second natural frequencies of most of the insulators were found to be less than 120 Hz, indicating that hazards are associated with the use of a single, spring-mounted mass to simulate their forced vibration in the design of substations. Measurements of the decay in their free vibration showed that the inherent damping of the insulators is no more important than the damping of the other structural elements in substations.