Study on the thermal expansion of EHV cable line with large size conductor in tunnel

In the tunnel, snake -like laying is the common but effective installation method for long length cable lines to absorb the thermal expansion that caused by load current of the cable conductor. 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 minish snake-like laying in size and hold cable lines as many as possible. 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 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 3000 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 circular brackets are the best design for the round cross section tunnel to save space.