• Journal of Environmental Impact Assessment
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• v.26 no.1
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• pp.11-26
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• 2017

Approximate empirical equations obtained by measuring overall noise levels at different distances have been used to evaluate environmental influence of the railway noise though the accurate prediction of noise levels is important. In this paper, a noise prediction model considering the frequency characteristics of noise sources and propagation was suggested to improve the accuracy of noise prediction. The railway noise source was assorted into track, wheel, traction and aerodynamic components and they were characterized with the source strength and speed coefficient at each octave-band frequency. Correction terms for the acoustic roughness and the track/bridge condition were introduced. The sound attenuation from a source to a receiver was calculated taking account of the geometrical divergence, atmospheric absorption, ground effect, diffraction at obstacles and directivity of source by applying ISO 9613-2. For obtaining the source strength and speed coefficients, the results of rolling noise model, numerical analysis and measurements of pass-by noise were analyzed. We compared the predicted and measured noise levels in various vehicles and tracks, and verified the accuracy of the present model. It is found that the present model gives less error than the conventional one, so that it can be applied to make the accurate prediction of railway noise effect and establish its countermeasures efficiently.

• KEPCO Journal on Electric Power and Energy
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• v.3 no.2
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• pp.79-88
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• 2017

In this paper, the wind tunnel test for the measurement of aerodynamic characteristics of transmission conductors with asymmetric sections is described. A single conductor model and bundled conductor models with ice accreted shapes are tested both in steady and turbulent flow, and the aerodynamic coefficients are acquired. Transmission conductor galloping is a kind of wind-induced vibration which is characterized by primarily vertical oscillation with a very low frequency and a high amplitude. It is well known that transmission conductor galloping is generally caused by moderately strong, steady winds when a transmission conductor has an asymmetric cross-section shaped by accreted ice. Galloping should be considered from the design stage of overhead lines because it can cause severe wear and fatigue damage to attachments as well as transmission conductors. It is reported that there have been normally 20 events of galloping per year in Korea, which may be followed by serious consequences in the electric power system. Therefore, this research is performed to measure aerodynamic characteristics of ice accreted transmission conductors to understand and control transmission conductor galloping so that it would help to prevent unexpected failures and reduce the maintenance costs caused by galloping.