Through the following explanation of the characteristics of OPGW optical cables and key points of installation control, construction personnel can have a general grasp of the key issues in OPGW line construction and establish a concept of OPGW line construction process and quality control, which has a positive guiding significance for engineering practice.
(1) Tension wire laying method
The commonly used installation and wiring method for OPGW is the tension wire laying method. The tension wire laying method uses a tension device to subject the OPGW to a certain constant tension during the entire wire laying process to ensure that there is enough clearance with obstacles and other objects to avoid friction and not damage the OPGW. At the same time, it can reduce compensation for young crops, reduce physical labor and improve construction progress.
(2) OPGW optical cable construction based on tension pay-off method
1、Guide rope method optical cable laying
The OPGW optical cable enters the tension machine wheel from the top, wraps around the tension wheel 6 times, and then leads out from the top. Use the traction net connector to fix the ground wire lead-out end, and use a 30kN rotary connector to connect the guide rope to the traction net (when connecting the optical cable, pay attention to check whether the optical cable model corresponds to the left and right ground wire brackets)
Lead the front end of the guide rope into the winch wheel from above the traction machine, and after winding the winch wheel for 6 turns, lead it from above to the guide rope drum, and install the grounding pulley on the guide rope and OPGW optical cable. After the preparation work of the tensioning and pulling field is completed, the pulling should be slow when starting. After the detwist device, traction net sleeve and anti-twist whip connected to the end of the optical cable pass through the first base tower, if the situation is normal, the pulling speed can be gradually and steadily increased to 30 meters/minute.
When the joint of the guide rope (i.e., 30kN bending connector) is pulled close to the traction machine, the pulling should be slowed down so that the joint passes slowly through the winch wheel of the traction machine. When the joint enters the guide rope drum for 2-3 turns, the pulling should be stopped. Anchor the guide rope with a wire clamp in front of the traction machine. Untie the bending connector of the guide rope joint, remove the fully wound guide rope drum, and replace it with an empty guide rope drum.
The removed guide rope drum should be promptly delivered to the designated location in the next line-laying section or recovered to the tool warehouse according to the plan. Wrap the guide rope head around the empty drum and tighten it. Start the traction machine and pause again after the force is applied. Remove the cable clamp and continue traction. After the optical cable passes the last pole tower, it should be sufficient for testing and connection. The reserved length at the traction end is 1 pole tower height plus 10 meters.
Stop traction and use the cable clamp to anchor the front and rear ends of the optical cable to the ground anchor. The ground of the anchor line should be connected in series with a 30KN hand hoist and tightened to maintain the tension of the ground wire or traction rope. Remove the traction rope, and the optical cable traction process is over.
2、Tightening
After the optical cable is deployed, the tightening construction should be carried out as soon as possible. The tightening should be carried out during the day, and the weather should be free of fog, rain and strong wind. According to the sag calculation table, the observation gear and the temperature and wind speed at that time should be selected, and the tightening method of tension release should be used to tighten the cable.
The tightening operation method is as follows: leave enough optical cable at the anchor end, the length is the tower height plus 10 meters, and then install the tension clamp on the side to be tightened. The tensioning of the optical cable with only one tension section is the same as the tensioning of the ordinary ground wire;
When tightening multiple tension sections that are not disconnected, the tensioning method from far to near should be adopted: that is, after tightening the tension section farthest from the tensioning side, mark it on the second tension tower, install the tension fittings and hang the wire on the tightened side, then relax the tension on the tightened side, take out the wire-laying pulley, install the hanging fittings and ground wires one by one on the straight pole tower, and leave enough optical cable on the tension tower (1.2 times the width of the crossarm), then install the tension clamp and hang the wire on the side to be tightened, and then tighten the next durable tension section, and so on.
Note that during the tensioning process, the surface of the OPGW optical cable should be protected by a rubber tube to prevent it from being scratched by the operation of the wedge and the tension pulley. Appropriate weight should be added during operation to prevent OPGW from being entangled. And use nylon rope to tie the cable to the hoist chain at the tension clamp of the optical cable to prevent excessive bending of the optical cable.
3、Observation and adjustment of curvature
Tighten the temporary guy wire of the anchor tower appropriately to make the cross arm hanging point deflect 30-50mm to the opposite side of the force. Start the capstan and tighten the OPGW. When the sag of the observation gear is close to the design sag value, the traction should be stopped. After the OPGW is stable, the sag observation should be carried out until the design requirements are met.
(a) Equal length method for sag observation
The equal length method is the parallelogram method. When conditions permit, the equal length method should be used first. Arrangement of sag observation by equal length method. When observing sag, make the connecting line of the planes on the two sag plates tangent to the lowest point of the overhead line, that is, the design requirements are met.
(b) Angle method for sag observation
In the tension section with large span, the theodolite angle method can be used for observation, and the span end method is generally used for observation. The schematic diagram of sag observation by the angle method is shown in Figure 4. The operating steps are: determine the position of the theodolite and verify the height difference between it and the observation point of the overhead line hanging point; calculate the sag observation angle θ at different temperatures; adjust the tight line sag so that the axis of the overhead line is tangent to the line of sight of the theodolite; conduct an inspection immediately after the overhead line is hung, and fill in the observation results in the sag record table.
(4) Installation of OPGW supporting hardware and accessories
The types of hardware used in the installation of OPGW optical cables usually include static end (tension) hardware, suspension (tangent) hardware, dampers, protective wires, lead clamps, grounding wires, intermediate junction boxes, terminal boxes, etc. It is particularly emphasized that the static end (tension) hardware dedicated to OPGW optical cables must be used when laying cables, pulling cables, and adjusting sag and tension to avoid damage to the OPGW optical cables.
To prevent vibration from wearing out the optical cables, the optical cables should not stay in the pulley for more than 48 hours after tightening the cables. Each set of hardware used for tightening cables can be reused up to three times depending on the operating conditions, and hardware used permanently in the project must be brand new.
(3)Key points for quality control of OPGW installation
1、The installation of OPGW optical cable is similar to that of power lines. During installation, the original transmission line must be shut down for operation. Construction is prohibited in severe weather such as strong winds, thunderstorms, severe cold and heat. The bending radius of the optical cable should be ensured to be above 0.5m.
2、During construction, it is necessary to avoid the optical cables from being entangled with each other and to avoid damage to the outer twisting layer of the optical cable. The dynamic bending cannot be less than 40 times the cable diameter, that is, during construction, it is necessary to ensure a bending radius of at least 600mm, and the OPGW optical cable cannot be twisted.
Special personnel shall be assigned to monitor at crossing points such as major traffic routes, communication lines, and power lines. The optical cable must be controlled at a safe height to avoid collision or crushing of the optical cable by motor vehicles, which may endanger the safety of the optical cable or personnel.
3、The requirements for the ground crossing distance of OPGW optical cable installation are: in unmanned areas, OPGW should be above 3m from the ground; on pedestrian roads and roads with few vehicles, OPGW should be above 5m from the ground; on highways and railways, OPGW should be above 7.5m from the ground.
4、During the construction process, pay attention to the protection of the outer layer of stranded wire. The outer layer of aluminum-clad steel wire or aluminum alloy wire is the carrier of overcurrent and lightning strike. If it is damaged, it will have long-term hidden dangers to the line. Check whether the pulley has burrs; do not throw or drop the optical cable; pay attention to the protection of the rubber sleeve when using the wire lifter. The OPGW optical cable drum is placed on a pay-off rack or cable drum car with a rotating shaft, and the distance between the cable drum and the center of the tension machine should be guaranteed to be 5-8m.
5、The construction of a single-drum optical cable should be completed every day. If it must be left overnight or for a long time, the OPGW optical cable must be fixed to the pulley with a nylon rope to prevent the optical cable from sliding and fatigue damage to the optical fiber at the contact point with the pulley. At the same time, the traction rope and optical cable should be temporarily anchored at the traction end and the tension end. The slack of the optical cable between the anchor point of the tension end and the tension machine is appropriate to relieve the tension on the tension machine. It cannot be too loose, and the optical cable must not be dragged on the ground.
Send Email 
WhatsApp
