Because of low temperature,deficient Oxygen and bad nature conditions at high elevations,it is difficult to construct for Qinghai-Xizang DC transmission project.In order to solve the low efficiency of the workers in the construction,the holding pole with modular mast section is developed,which has components of light weight and occupies little space in transportation,effectively reducing labor intensity in site handling,achieving convenient mechanical transport and improving construction safety.

The paper illustrates the principle of metal deformation when compressed and conductor deformation process when compressed for connection,analyzes several causes to produce untwisted strands of large-sectional conductor during its compression for connection.It also puts forward several methods including increasing compressor pressure,optimizing mould design and changing compressive directions to eliminate untwisted strands.

Combining with foundation design characteristics in Xiangjiaba-Shanghai ±800 kV UHVDC transmission project,the rotary drill rig for excavated foundation was developed,which were tested for excavated foundations in-situ and applied in typical tower place of BN157 and BN162.Compared with artificially excavated foundations,the technique avoided personnel risk,possessed economy benefit and society benefit,deserved application in power transmission lines.