The design values of the unbalanced tension given in existing specification are quite different from the values taken for actual engineering.To investigate the longitudinal load characteristics of large cross-section conductors in heavy icing area

a calculation model for unbalanced tension of continuous span is established.The calculation program is coded with VB language.According to the typical design conditions of UHVDC transmission lines

the unbalanced tensions of suspension tower and tension tower are calculated.The sensitivities of the influencing factors

such as span

height difference

suspension string length

conductor diameter

icing rate

span nonuniformity

and ice thickness

are calculated and analysed.It is suggested that for large cross-section conductor in heavy icing area

larger unbalanced tension of tension tower and smaller unbalanced tension of suspension tower should b e taken

and particularly

graded values of the unbalanced tension could be taken according to different working conditions.