Cable layingCable laying sub trunk cable, feeder cable, grounding cable. 1, preliminary inspection: the installation route route by the verification site conditions determine the cable laying mode: the existing pre buried pipeline or other units construction and buried pipeline should be pre tested to ensure that the cable can be laid normally. In the tunnel construction, we should focus on the inspection of the cable trench to the distribution box preburied pipe, the distribution box to the bridge preburied pipe and the arc pre buried pipe. Negotiate and deal with the scheme and deal with it as soon as possible. 2. Installation of cable trench bracket: first, we need to measure the cable trench in the trench laying cable, design the cable trench size according to the actual situation, and purchase in time. When the installation is done, the baseline is drawn first, then the installation position of the bracket is determined to install again, so as to ensure the height of the support is consistent. 3, cable trench laying flat steel: cable trench laying cable, the ground wire is flat steel, then the ground flat steel will be welded before laying the cable. Flat steel needs anti-corrosion treatment, flat steel connection must be full welding, the length of flat steel should be more than 2 times the width of the flat steel, the flat steel should be welded with each cable trench support firmly, and connect to the grounding electrode at a certain distance, the corrosion treatment of the welding process, and the joint grounding of the flat steel at the exit. 4. Laying of main cables: laying of main cables and installation of bridges. (1) laying in the cable trench: the cable is laid on the bracket horizontally, and the long distance power cable or the coarse cable are laid on the lower layer (when there is a high voltage power or control cable, the high voltage cable is at the bottom, followed by the control cable, and finally the power cable. " Short distance cable cables or thin power cables are located at the top level. It is forbidden to overlap the cables and lay a certain allowance in the installation so as not to shorten the cable tension. The cable should be fixed and secured at every cable trench support, and the appropriate allowance should be left when the cable comes in and out to control the distribution box. (2), bridge laying: the cable is laid on the bridge horizontally, the long distance cable is laid on the outside, the short distance cable is laid in the inner test, and the overlapping pressure of the cable crossover is avoided, and some allowance is left to avoid the cable shortening. The cables are strapped and fixed every 1m-1.5m. When the cable enters and controls the distribution box, there must be an appropriate margin. 5, line cable laying: the tunnel lighting branch cable is usually laid on the bridge and connected with the lamps and lanterns. The general connection methods are divided into the pre branch cable connection, the puncture line clip connection and the ordinary dry bag connection. The wiring of lamps and lanterns is circularly connected according to A, B and C three-phase fire lines, so as to ensure three phase current balance. The insulation treatment of the interface and branch cable must be well handled in the wiring of the feeder cable. There is a suitable margin for the branch cable in the bridge and the control box. The laying of the evacuation indicator is usually laid in the cable trench or in the pipe laying, and connected with the lamps and lanterns. The connection methods are divided into the pre - branch cable connection, the puncture line clip connection and the ordinary dry bag connection. The wiring of lamps and lanterns is circularly connected according to A, B and C three-phase fire lines, so as to ensure three phase current balance. The appropriate allowance should be reserved for cable laying. When pipe laying is done, it is necessary to pre test the buried pipe before testing, and then wear the thread if there is no problem. 6, grounding cable laying: the cable groove ground wire usually adopts flat steel grounding, the cross section of grounding wire is 40x4 galvanized flat steel or 16 round steel in diameter. The grounding wire is connected to the ground electrode at a certain distance at each interval. The connection place needs electric welding or gas welding, the weld is used for anti-corrosion treatment and the ground moving distance is determined by design. Generally, it is suitable for 5 meters. The grounding wire of the bridge generally adopts flat steel or copper core cable, and is connected by the buried pipe to the ground wire through the cable trench or with the ground pole at a certain distance. 7, cable signs: for connection and after maintenance convenient, each cable must have signs, indicating the cable circuit number, starting point, terminal phase cable model. There must be signs at both ends of the parent bar circuit. In the route, there must be signs for each cable shaft, bend, and cable bifurcation. The other routes must be marked at 5-10 meters each.