Key word: Power Cable, Thermal Expansion, Large Size Conductor, Cable Installation, Calculation, Analysis

Abstract For absorbing thermal expansion that caused by load current of the cable conductor, snake-like laying is the common but effective installation method for long length cable lines. Especially, the inner mechanical stress formed by thermal expansion of EHV power cable lines with large size conductor imperils the joints and terminations of cable lines which installed in the tunnel. It is well known that space in the tunnel is narrow and limited. However, the snake-like laying needs large space. The construction cost of the tunnel would be increased unless minishing snake-like laying in size and installing cable lines as many as possible in the tunnel. So, thermal expansion of long length power cable line with large cross section of conductor can not be neglected. In this paper, two kinds of EHV cable lines are taken for analytical examples to calculate thermal expansion quantity. One is 2500 mm2 / 220 kV XLPE cable line that its route length is about 1.2 km and another is 2500 mm2 / 500 kV XLPE cable line that its route length is about 17.15 km. The calculation results proved that optimal design of snake-like laying in size and distribution of bracket can economize space greatly in the tunnel. In other words, the arc amplitude range from 150 to 250 mm and the pitch range from 4000 to 8000 mm are enough for the snake-like laying of the long length cable lines with large size conductors that installed in the tunnel. And the arc brackets are the best design for the rounded cross section tunnel to save space.