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.
INFLUENCE OF TRANSMISSION-LINE PARAMETERS ON HIGH-AMPLITUDE VIBRATION OF CONDUCTOR BUNDLES
The influence of transmission-line parameters on high-amplitude cable vibration was studied numerically on a bundle of two conductors. Such line parameters as span length, number of spacers in a span, and suspension length were varied, because they have great influence on the severity of vibration. The high-amplitude vibration was initiated by load removal simulating ice shedding from an entire span of a transmission line, and the severity of vibration was evaluated by determining conductor rebound height and angle of bundle rotation. The numerical model was developed using the commercial finite element analysis software ADINA. Results show that when the initial horizontal tension is kept constant, the conductor jump increases with span length for the shortest spans, and it varies in a limited interval for the longest spans. When the sag-to-span ratio is kept constant, the conductor jump increases with span length even for the longest spans considered. The bundle rotation may increase considerably with span length; however, if the number of spacers is great enough, then the span length may not affect the bundle rotation significantly. The bundle rotation is independent of the suspension length even when only one spacer is applied in the entire span, but the conductor jump increases considerably with suspension length. The severity of vibration of conductor bundles depends on several transmission-line parameters. Some of these parameters have particularly important effects when the conductor vibrates with high amplitude as is the case in different processes occurring occasionally in cold regions, e.g. during galloping, after ice shedding, after the application of a shock load for ice removal, or following conductor breakage. These line parameters include span length, number of spacers in a span, and suspension length; and they influence significantly the vibra- tion amplitude, or the conductor rebound height, and the angle of bundle rotation. The predic- tion of these parameters is particularly important for avoiding flashover, bundle collapse, and further related problems in the transmission line. A review of ice-related dynamic problems on overhead lines, including ice shedding and bundle rolling is provided in (3). These prob-
Morphological characterization of Eustrongylides sp. larvae (Nematoda, Dioctophymatoidea) parasite of Rhinella marina (Amphibia: Bufonidae) from Eastern Amazonia.
Absctract Eustrongylides spp. nematodes have birds as final hosts and uses other vertebrates as intermediate/paratenic host (fish, amphibians and reptiles) and have zoonotic potential. In amphibians, the larvae may be located in the subcutaneous tissues, liver and mesentery, between the muscle fibres, especially in the lower limbs. Rhinella marina, which is widely observed in Brazil, has exhibited complex diversity in its helminth fauna, reflecting the unique habitat of the Amazon biome. For the first time, this study describes the morphological aspects of third-stage larvae of Eustrongylides sp. in Rhinella marina from Santa Cruz do Ararí, Marajó Archipelago, Eastern Amazonia, using light and scanning electron microscopy.