Modelling of Vibrations of Overhead Line Conductors by Giorgio Diana

Author:Giorgio Diana
Language: eng
Format: epub
Publisher: Springer International Publishing, Cham

Giorgio Diana

Email: [email protected]

3.1 Introduction

The first two chapters cover the modelling of aeolian vibration of an undamped single conductor and of a single conductor plus one damper. This chapter defines the expected vibration level and assesses the uncertainties associated with the present technology based on the energy balance principle (EBP) and a shaker-based approach. It has been shown that analytical methods based on the EBP and a shaker-based technology can provide a useful design tool for damping systems that protect a single conductor against aeolian vibration.

The purpose of the present chapter is to evaluate the effectiveness of these methods for the design and/or verification of the damping system of long, single conductor spans strung at relatively high tensile load, such as crossings, which need more than one damper per span extremity to be effectively damped against aeolian vibration.

As in the first two chapters, this chapter is based on an analysis of the available technology and on the results of two benchmarks: an analytical–analytical benchmark and analytical–experimental one. The comparison between the analytical results produced by the different available models and the experimental one will help to understand the limitations and the usefulness of the approach.

Some difficulty in finding the data for the analytical–experimental benchmark has been experienced by the WG members and consequently, the specific case of the Messina crossing in Italy was chosen but this does not limit the validity of the assessment.

The application of the EBP technology is more critical for long spans than for normal length spans discussed in the two previous chapters. The EBP in the previous chapters is based on a constant mean wind speed along the entire span but the longer the span length, the more unrealistic it would be to have a constant mean wind along the entire span, especially at the low wind speeds required to produce aeolian vibration. The tensile load variation along the span also becomes significant for large sags and it affects the conductor vibration wavelength.

It must be pointed out that EBP-based methods do not simulate the full complexity of the problem. More sophisticated methods (Rawlins 2000; Giorgio et al. 2009, 2010) can be used to account for the effect of the mean wind speed variation in time and space and wind turbulence, but these are still at a research stage and are not within the scope of this work.

However, the use of the EBP approach, i.e. the assumption of a constant wind speed along the span, for long span applications should guarantee predicted vibration amplitudes higher than those that occur in reality, therefore producing conservative damping system designs.

Outline of the technology

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