Wind tunnel and analytical investigations into the aeroelastic behaviour of bundled conductors

The conditions for bundle instability were determined for spring-mounted, sectional models in the wind tunnel. The stability boundaries are in good agreement with predicted values from a quasi-steady analysis using measured mean forces. The analytical model was extended to a three-dimensional, multi-subspan catenary. Predictions were compared to some observations from a full-scale line and from a reduced scale span in a large wind tunnel. Experimental and analytical studies showed that twisting the bundle through 30 degrees per subspan prevents subspan oscillation. Extensive wake measurements suggest that some of the mean vertical force on downstream conductors is due to wake static pressure gradients.