The rating current (ampacity) of a conductor erected on a particular overhead line (OHL) structure installed at a specified location is influenced by the conductor, the OHL structure as well as weather and operational parameters. Many studies have been carried out regarding calculating an aerial bare conductor's ampacity at a steady-state conductor temperature, but without considering the OHL structure as part of the system. In this paper, a holistic methodology for calculating the conductor's ampacity and sag at any temperature and power frequency, erected onto a pre-specified OHL structure is developed, considering together the mechanical and electrical parameters of the overall system. This methodology incorporates the conductor's basic material properties allowing the calculations to be applied to newly developed high temperature low sag composite conductors. In this way it becomes possible to identify, at system level, the potential benefits that may result from the improved performance of these conductors as well as to indicate new sizes that may better fit a pre-specified system, optimizing its performance. The methodology is also validated with a real system application, resulting in correct predictions of the performance of a 4-span double line system.
A holistic computational methodology is employed in this paper to present an analysis of the widely used aluminum alloy conductors (AAAC) performance on a 33-kV wood pole structure. This analysis highlights the basic system properties that influence its mechanical and electrical performance. A comprehensive comparison of the performance of the common AAAC and aluminum conductor steel reinforced (ACSR) conductors erected on the structure is presented, including the study of the increase in operating temperature on the losses, ampacity and sag, in order to identify the most appropriate conductor for the pre-specified structure. Some recently developed high temperature low sag (HTLS) composite conductors are also studied in terms of power transfer uprating on distribution overhead lines. Their performance is examined at normal temperatures instead of the high operating temperatures for which they are specifically designed for, in order to evaluate the benefits they may offer at distribution level voltages. Index Terms-Aluminum alloy conductors (AAAC), aluminum conductor steel reinforced (ACSR), ampacity, high temperature, high-temperature low sag (HTLS), reconductoring, sag.
Background:The aim was to compare the retinal nerve fibre layer (RNFL) thickness and visual evoked potentials (VEP) among eyes with multiple sclerosis (MS)-associated optic neuritis, unaffected eyes of the same patients and eyes of disease-free controls. Changes in RNFL thickness, visual acuity (VA) and VEP over time are evaluated in MS-associated optic neuritis. Methods: Forty-six eyes of 23 patients (six male and 17 female), who suffer from MS and were diagnosed with unilateral or bilateral optic neuritis, participated in the study. Forty eyes of 20 age-and gender-matched controls were tested. VA measurement, optical coherence tomography and VEP were performed in all patients at presentation and at one, three and six months thereafter. Results: There was a statistically significant difference in VA between MS eyes with optic neuritis and controls (p < 0.0001), as well as between MS eyes with and without optic neuritis (p < 0.005). VA improved over time. Average RNFL thickness was reduced in MS eyes with or without optic neuritis in comparison to control eyes. This reduction in RNFL thickness was more marked over time. The amplitude of P 100 was significantly decreased in MS eyes with optic neuritis in comparison to controls (p < 0.0001) and there was a statistically significant delay in peak time of P100 in MS eyes with optic neuritis versus the eyes of normal subjects (p < 0.0001), which improved over time.
Conclusion:The present study suggests that there is a progressive decrease in RNFL over time in eyes with optic neuritis associated with MS. The amplitude and latency of P100 in VEP examination returned to normal ranges over time.
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