Large amplitude vibrations of long-span transmission lines with bundled conductors in gusty wind

• Full-scale measurement data of three types of long-span transmission line system is analysed.
• Finite element models of three types of transmission line system are proposed.
• The field vibration are interpreted based on result of the data and modal analyses.
• Gust response analysis is reproduced in frequency domain by buffeting theory.
• The results concluded that gust response can be large enough to cause damages.

Large amplitude wind-induced vibrations of ice-accreted/unaccreted conductors in overhead transmission lines are frequently observed in the field. Damage due to the large vibrations is costly and affects many aspects of modern society. In this study, an attempt is made to identify the large amplitude gust responses and to distinguish them from the unstable phenomena of galloping in field-observed vibrations of long-span-overhead transmission lines that have bundled conductors. An extensive method of combining field-measured data analysis, eigenvalue analysis and gust response analysis is applied. The field-measured wind and vibration characteristics and their relations are first discussed to study preliminarily the types of field-measured responses. Next, the natural frequencies and mode shapes of the transmission lines are estimated by eigenvalue analysis using reliably created finite element models to verify the field-measured response characteristics in the frequency domain. Gust response analysis is finally conducted to interpret intensively the large-amplitude gust responses of overhead conductors, and results in good agreement with field-measured vibrations. Through this extensive study, it is concluded that most of the field-measured responses are gust-type vibrations and that a gust response can be sufficiently large to cause damage in the overhead transmission lines, regardless of their type.