Experimental study on torsional behavior of twin bundle conductor lines

The torsional behavior of twin bundle conductor lines is investigated by means of experiments. Based on similarity principle, the reduced-scale modelling method for simulating the torsional behavior of bundle conductor lines is presented and validated by the test results of full-scale transmission lines. Parameter study on torsional behavior of twin bundle conductor lines under different parameters, including loading and unloading rates of applying torque, initial tension in sub-conductors, layout of sub-conductors, number of spacers, clamps between spacers and sub-conductors and arrangement of spacers, is carried out by means of reduced-scale modelling tests. The effects of these parameters on the torsional stiffness, collapse moment, collapse angle, self-restoring moment of twin bundle conductor lines are obtained. It is observed that a collapsed bundle conductor line may not be able to return to its initial position after releasing load, which reflects the phenomenon observed in real transmission lines, and optimal arrangement of spacers in a bundle conductor line may exist to prevent or mitigate the torsional instability in the case without considering other factors such as sub-span oscillation. The presented reduced-scale modelling method and test results provide a foundation for further understanding of torsional instability and control of bundle conductors rolling.