Strength Assessment of Deteriorated OHL Conductors and Earth Wires Based on Non-Destructive Testing

Safety operation of overhead lines depends on many factors including strength of conductors and earth wires. Therefore worn-out or defective conductors or earth wires must be detected. Estimation of conductor technical conditions is based on comparison of revealed flaws with requirements of overhead line project and build documentation. It is well known that conductors are affected by corrosion, friction and fatigue wear. All this factors may cause loss of strength and even breakage of conductor. Steel core is the most important part of conductor when it comes to mechanical loads. That is why it is very important to know actual technical conditions of steel core of conductor. Worn or defective wires must be repaired or replaced. Principles of strength assessment of deteriorated of steel-aluminum conductors and steel earth wires based on magnetic non-destructive testing technique are presented. The retention of overhead line conductor and earth wire is one of the most reasonable ways to eliminate the unacceptable clearances. The allowable magnifying tension, regarding the reliable operation, is set relying upon the non-destructive testing of conductors or earth wires in actual state. The measured loss of metallic cross-section area due to abrasion, corrosion etc. and local wire breaks are treated as input data for mechanical model of objects under test. The residual strength estimates give the specialists network company further information that helps to make a valid decision on testing time-limit and policy. Some results of assessing the strength of overhead line conductors and earth wires according to the NDT data are demonstrated.

Modelling the risk of collision with power lines in Bonelli’s Eagle Hieraaetus fasciatus and its conservation implications

SummaryPower line casualties are considered one of the main causes of mortality in the endangered Bonelli’s Eagle Hieraaetus fasciatus, although little is known about factors involved in collisions with wires and their consequences at population level. We studied 18 radio-tracked individuals to determine the risk of collision with power lines at two spatial scales (flight height and span crossings). Through logistic regression modelling we found that the risk of collision was mainly determined by eagles’ home range use, being reduced in kernel 80%, kernel 95% and MCP respectively to 0.421, 0.114 and 0.032 times in comparison to risk associated to the 50% kernel area. In addition, the risk of collision increased in open habitats (around 1.5 times higher than in forested habitats) far from urban areas (2.345 times higher than near urban areas) that were good for hunting, and in cliff areas used for breeding and roosting, where eagles fly at a lower height (the probability of eagles flying at a low height was 1.470 times higher than in forested habitats). A significant positive correlation was found between territorial turnover rates and the risk ascribed to transmission lines with earth wires in 15 breeding territories. Moreover, this correlation had a higher significance for the 50% kernel area when transmission without earth wires and double circuit distribution lines were added, although no correlations were encountered for distribution lines. These results suggested that power line collisions might be more important than previously reported as a cause of mortality for the species and thus conservation actions should be applied in order to minimise their effects on population dynamics. Predictive models may be a useful tool in careful planning of new power line routes and the wire-marking of the existing ones. Kernel areas should be used rather than fixed radii given that distances from nests may not adequately match the risk of collision.