1. Greasy dirt on the wire surface
Overhead ACSR cables used for overhead transmission lines are often questioned by customers or even returned due to surface quality problems. This phenomenon is mainly caused in the drawing process. The main reasons are as follows:
(1) The size of the finished wire drawing die is too large, the compression is relatively small, and the working area of the wire drawing die is short, which is not enough to remove the oil on the surface of the wire;
(2) The temperature of the lubricating grease is too low, the viscosity is large, and it is not easy to play, causing the drawing oil to adhere to the surface of the aluminum wire;
(3) The thread rubbing felt at the exit of the finished mold is too dirty;
(4) When stranding the wire, the stranding machine body or the traction wheel is too dirty;
(5) There is too much water under the traction wheel.
For the above reasons, in order to avoid the generation of oil stains on the wire surface, select a suitable wire drawing die and adjust the temperature of the lubricating grease during wire drawing; frequently replace the wire rubbing felt, and keep the stranding equipment and mold clean and free of oil when stranding the wire.
2. The wire surface is scratched
Since there are sharp metal objects in the wire drawing equipment and ACSR Cable drawing die or the wire stranding equipment and the wire stranding die, it is easy to cause surface scratches when the wire is drawn or the wires are stranded. This kind of defect firstly affects the surface quality of the wire, and secondly, corona occurs due to the unevenness of the conductor when the wire is running. Therefore, once the surface scratches are found, the cause should be investigated immediately from the equipment or mold.
3. Wire scratches
Continuous scratches on wires are the most common cause of corona, and corona is one of the most important causes of power loss in power systems. In order to avoid the occurrence of wire scratches, the following aspects should be controlled in production: firstly, consider the conductor itself. First, ensure that the aluminum rod is not damp. The aluminum rod is damp, causing aluminum chips to stay in the working area of the drawing die hole, and the lubricating oil cannot be used. All enter the work area, resulting in the drawn aluminum wire is not round and not smooth. Second, ensure that the drawing oil is clean and free of moisture. In the process of drawing, the drawing oil is in a high temperature state when it enters the work area from the lubricating area. If it contains a certain amount of moisture, the lubricating oil will be diluted and the lubricating effect will be greatly reduced, resulting in wire scratches and aluminum wire breakage.
Secondly, from the perspective of production, the following issues should be paid attention to:
In the drawing process:
(1) Check whether the mold of the wire drawing machine is placed accurately;
(2) Check whether the drawing drum has a groove after friction, and whether there is a crimping phenomenon;
(3) Check whether the surface finish of the lubrication area of the drawing die meets the requirements, and whether there is blockage by aluminum chips.
In the stranding process:
(1) Check the sensitivity of the top of the spool;
(2) Check whether the tension of the spool is uniform;
(3) Check whether the single wire is slightly crimped or the wire is uneven;
(4) Check whether the single wire is in the groove of the guide wheel during twisting.
4. Loose wires and serpentine bends
(1) Adjust the pay-off tension of the wire reel when twisting the wire. The tension depends on the accumulation of experience in normal work. Generally, experienced operators should be able to adjust the tension to the appropriate requirements;
(2) When selecting the parallel mode first, the diameter of the parallel mode is required to be 0.3-0.5mm smaller than the outer diameter of the stranded wire;
(3) Adjust the back-twisting device to make the single wire “S” before twisting, so as to eliminate the internal stress generated by the single wire during the twisting process;
(4) Minimize the number of stops during the stranding process. It is best to produce the same stranded wire at the same fixed speed to prevent uneven speeds or parking/driving.
(5) Check in advance to use the steel core for stranding to ensure that there is no looseness; when the wire is stranded, the steel core should maintain a sufficient constant pay-off tension.