Abstract: By applying the scheme of stretching the V-string into the tower body, the length of the cross arm of ±1 100 kV transmission tower can be shorten. As a result, the tower weight and the corridor width can be reduced. The V-string offset with broken iced conductors is an important controlling parameter for determining the layout scheme of V-string stretching into the tower body. Accurate calculation of the dynamic unbalanced tension forces of the broken iced conductor can provide the basis for checking the structural strength of the lighting protectors of transmission lines. A seven-span conductor-V-string finite element analysis(FEA) model of ±1 100 kV line section is established with general software ANSYS. The initial tension force of conductors can be applied by lowing temperature method. The damping of the conductor-V-string system is realized by Rayleigh damping form. Four sub-conductors are assumed to be broken simultaneously. The conductor elements at the broken point are killed for realizing the broken conductor simulation. By using nonlinear transient analysing method, the time histories of the V-string offset and the unbalanced tension forces at the suspension point with and without sub-spacers are calculated. When considering the effect of the sub-spacers, the peak values of the V-string offset and the unbalanced tension forces are lower than the design values calculated by static model without sub-spacers. It is safe to determine the scheme of V-string stretching into the tower body and the unbalanced tension forces according to design values.

Key words: broken conductors, V-string, offset, unbalanced tension force, sub-spacer