Modeling Sudden Ice Shedding From Conductor Bundles
Sudden ice shedding from conductor bundles was modeled numerically and experimentally by improving the approaches proposed formerly for a single cable. The experimental study was carried out on a small-scale laboratory model of one span of a twin bundle. A numerical model of the experimental setup was developed using the commercial finite-element software ADINA. This model was validated by simulating: 1) the vertical cable vibration during former load shedding tests on a full-scale line of single conductors; 2) the bundle rotation on a full-scale twin bundle during former static torsional tests; and 3) the vertical cable vibration and bundle rotation at midspan during the present load shedding tests on a small-scale twin bundle. The coincidence of calculated and measured tendencies justified the applicability of the numerical model to simulate the vibration following ice shedding from bundled conductors in most cases. The model was finally applied to simulate sudden ice shedding from a full-scale span with a twin bundle. Simulation results showed that the application of spacers reduces the cable jump height during this vibration; however, a higher number of spacers in the same span does not decrease the angle of bundle rotation.
Vibration of Bundled Conductors Following Ice Shedding
The dynamic behavior of bundled conductors following ice shedding from one subconductor is examined numerically using the finite-element method. An existing model of ice shedding from a single conductor is improved by developing a model of spacers which connect subconductors in the span. The resulting system makes it possible to simulate vibrations following ice shedding from one span of an overhead transmission line with twin, triple, or quad bundles. Vibration characteristics are evaluated as the following parameters are varied: thickness of shed ice, distance between adjacent spacers, and number of subconductors in the bundle. Simulation results will provide information on how the amplitude of vibration and the transient dynamic forces change with the application of spacers. The maximum jump height of the ice-shedding cable, the maximum drop of the loaded cable, and the maximum cable tension are approximated as power functions of ice thickness and the distance between adjacent spacers.
Field Observations on Wind-Induced Conductor Motions
Abstract This paper presents a collection of a number of observations made on a full-scale experimental line concerning the vibrational behaviour of electrical conductors under the effect of natural winds. It is shown that both (Strouhal) frequency and amplitude of Aeolian vibrations are practically unaffected by the component of wind velocity parallel to the conductor. While increased wind turbulence appears to attenuate vibration amplitudes, higher conductor tension has been shown to exacerbate conductor sensitivity to vibrations. Examples of the low Aeolian-vibration response of bundled conductors equipped with damping spacers are reported and discussed. Wake-induced oscillations of bundled conductors are first investigated regarding constituent modes and frequencies. The severity of oscillations is then dealt with by means of an instability index which is used to reveal dependency upon wind velocity and angle of incidence, conductor tension and spacing-to-diameter ratio, bundle configuration and tilt angle, as well as diameter ratio, bundle configuration and tilt angle, as well as damping spacer type and number.