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.

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.

Ice shedding propagation on a single conductor and on a circuit of three conductors in a vertical configuration where conductors are linked with interphase spacers was modeled numerically. Several concentrated loads acting along the loaded span modeled the ice, and the shedding propagation was then simulated through the removal in a defined sequence of these concentrated loads. The model determines conductor displacement and the variation of conductor tension during the vibration following ice shedding propagation; and, thus, it predicts conductor rebound height, tension peak, and to what extent the conductor clearance is reduced during vibration. Ice shedding propagation on the full-scale test line of Hydro-Quebec was considered, and the model was validated by comparing simulation results to former experimental observations. The results show that the application of spacers reduces the severity of vibration considerably, and consequently increases the conductor clearance and reduces the risk of flashover. The dynamic effects of different shedding processes were also compared. The rebound height is the greatest for a single conductor when ice detachment propagates along the conductor, but then ice falls suddenly as a big chunk. However, the consequences of sudden detachment and shedding are obtained as the most severe when conductors are linked with spacers.