This project is named Transmission Line Project of Sri Lanka Puttalam Phase Ⅱ 2×300MW Coal Power Plant, which is start from Puttalam Power Plant and end in Anuradhapura substation with total length of 97.652km. There are Puttalam Lagoon, salt field, coconut grove and wildlife sanctuary along the line route. The traffic condition is bad with crisscrossed ditches and rivers. The intervisibility is so terrible due to 80% of the line route is covered by forest and dense vegetation. 2×AAAC-400 will be adopted as the guide line and 2 pieces of OPGW1 with 12 cores will be used as the ground wire.
The optical cable from N57 to N70 needs replacement because of part of the optical fiber around N59 was broken; besides, crossing structure should be built at four places and the power cut is necessary by reason of one 33kV power line and A12 road is crossed by N60-N61, one asphalt road is crossed by N63-N64 and one 33kV power line is crossed by N64-N65.
三．Planned Construction Period
3.1、The crossing structures are planned to complete in 6 days.
3.2、6 days are planned to dismantle hardware fittings and hang the tackles for 14 towers, please note that power of double circuits of 220kV transmission line should be cut at the same time for construction;
3.3、It takes about 2 days to replace OPGW cable with total length of 5483m, please note that power of double circuits of 220kV transmission line should be cut at the same time for construction;
3.4、It takes about 2 days to fasten the cable and adjust the line sag, please note that power of double circuits of 220kV transmission line should be cut at the same time for construction;
3.5、5 days are planned to install the hardware fittings and accessories of 14 towers, please note that power of double circuits of 220kV transmission line should be cut at the same time for construction;
Total construction period is 21 days, of which 15 days need power cut simultaneously of the double circuits of 220kV transmission line.
四． Construction Preparation and Method
4.1 Preparations before Power Cut
4.1.1 Firstly, the technical director, construction manager and other relevant people should make filed investigation, then work out the most feasible construction method, and finally put forward the construction scheme.
4.1.2 The hardware fittings and materials should be ready in quantity before power cut construction. Issues such as whether the hanging hole matches the connection points of the first hardware fitting (refer to the tower drawing and hardware fittings installation drawing), trial assembly of fittings, quantity of fittings and whether the spare parts (such as cotter, spacer pins and so on) are available, if not, prepare them by yourself.
4.1.3 Before power cut construction, the technical director should give technical disclosure and safety disclosure to all the constructors, clarify the construction requirements and determine the division of work.
4.1.4 Make contact with the power supply department and submit the outage application to them.
4.1.5 Transport all the required materials, tools and instruments to the construction site, check and take care of them, meanwhile the construction site should be arranged well.
4.1.6 Build the crossing structure.
4.2 The Basic Construction Method after Power Cut
4.2.1 Firstly, make sure that 220kV power has been cut through checking the power by test pen after power cut, and then finish the working earthing at the big number side of tower N50 and small number side of tower N77 separately for 220kV transmission line project.
4.2.2 Lift the existing cable, remove the hardware fittings from N57 to N70 in sequence and then install φ508 gin block, meanwhile, put the existing cable into the block.
4.2.3 Draw out the surplus cable of N57 and N70 from the rack, do not damage the optical fiber of both end of the joint box, and prevent the armor layer of the cable from scratching with pulley groove, tower body or other obstacles.
4.2.4 Tension paying-off method will be used for cable replacement, which means using the existing cable pull the new cable for paying-off. Due to the tractive force is known as 12.8kN and the tensile force is known as 11kN through calculation during this section, SAYQ90D dragger and WZT40×2-1.5 hydraulic tensioner is selected.
4.2.5 Fasten the cable and adjust the sag after cable paying-off. Someone should be assigned along the line route in order to prevent the cable from abrading by obstacles and from slipping out from the pulley groove during cable fastening. Special people and adequate communication equipment should be equipped for each tower, especially for the strain tower and suspension angle tower so as to handle with and eliminate the possible problems.