Author: Noyafa–Cable Tester Manufacturer
Repair of damaged cables: What are the solutions for repair of damaged cables? Cables are very common in our daily life. Generally, cable damage is a very troublesome thing, and professional cable repair companies can handle them with ease. The following editor will introduce you to the repair of damaged cables in detail: the solutions for repairing damaged cables, which cables are very common in our daily life, generally cable damage is a very troublesome thing, and a professional cable repair company can handle it with ease . The following editor will introduce the solutions for repairing damaged cables in detail. At present, 8.7/10kV cables are used in the transformation of the urban network 6kV system. The insulation thickness of the cables is 4.5mm, while the 6/10kV cables The insulation thickness is 3.4mm.
Due to the increase of the insulation thickness of the cable, the field strength is reduced, which can prevent the aging of the water tree. At the same time, due to the single-phase grounding of the 6kV neutral point low-current grounding system, the cable must withstand 1.73 times the phase voltage, and it must be operated as required. 2 hours, therefore, it is necessary to thicken the cable insulation. (2) Since impurities and pores in the insulation are the starting point for the occurrence of water trees, the quality of the cable is very important to prevent the aging of water trees. When purchasing cables, you must choose a manufacturer with excellent quality, carry out strict tests on the samples submitted by each manufacturer, and require each manufacturer to bid, and select high-quality and low-cost products.
(3) Ensure that the cable head is well sealed. For the sawed cable end, whether it is stacked or laid, it must be sealed with plastic, and a special cable gland is used to prevent moisture from infiltrating. (4) The cable head should be made in time after the wire is laid. If it is really impossible to make it immediately due to conditions, the cable head should be sealed and wrapped and placed overhead. (5) Repairing damaged cables improves the technical quality of construction personnel and strengthens the management of the cable head production process, which can effectively prevent the cable head from entering water during the production process.
Practice has proved that once the cable enters the water, the earliest breakdown phenomenon is often the cable head, so the wire head is well made, which can prolong the overall life of the cable. For example, when the cable is stripping the semiconductor layer, we must first make a circular cut on the semiconductor layer according to the specified size, then make a few vertical lines, and then strip the semiconductor one by one along the cut. When scratching with a knife, the force must be properly grasped. If the scratch is too shallow, the semiconductor layer will be difficult to peel off. If the scratch is too deep, the insulating layer will be damaged, which will bring opportunities for the formation of water trees.
When there is a cable that cannot be stripped by the semiconductor, the semiconductor layer must be scraped off with a glass sheet, which requires the construction personnel to be careful and careful, not only to clean the semiconductor layer, but also to avoid damage to the main insulation as much as possible. Be sure to sand the primary insulating surface smooth. In addition, when the heat shrinkable head is soldered, some damaged cable repair construction workers often use a blowtorch to melt the solder directly to save trouble. At this time, the flame will damage the copper shielding layer and the insulating layer, so pay attention to prevent the on-site production. occurrence of such phenomena. When the heat shrinkable material is heated and hardened, it is no longer elastic, which is determined by its material properties.
During long-term operation, due to thermal expansion and cold contraction, tiny gaps will gradually be formed at the junction of cables, resulting in intrusion of water vapor. In view of this, at present, our company has basically eliminated the heat shrinkable head, and generally adopts the silicone rubber cold shrinkable cable accessories produced by 3M company. No solder needed. In addition, the silicone rubber cold-shrinkable material has stable performance and elasticity, can be tightly attached to the cable, and will not crack after long-term use, which effectively overcomes the shortcomings of the heat-shrinkable material.
(6) When the cable is directly buried, we use the new PP-R plastic pipe as the casing. The pipe is corrosion-resistant, has a smooth inner wall, and has good strength and toughness, which can greatly reduce the probability of cable damage. (7) Due to the limitation of conditions, the local cable laying is in the form of direct burial or cable trench. We are located in the coastal area, where the local area is mostly saline-alkali land. In addition, the drainage is not smooth, resulting in frequent accumulation of water in the cable trench or cable well. Therefore, in the early planning for the repair of damaged cables, the design of cable trenches, culverts and cable wells should be coordinated with the civil construction party in time to facilitate the drainage of cable trenches (wells).
At the same time, the brackets are embedded in the cable trench to support the cables with brackets. In addition, in view of the current situation of numerous petrochemical enterprises within the jurisdiction of Shengli Oilfield, the nearby cable trenches must have complete drainage facilities. When designing the cable culvert, it should be as straight as possible to reduce elbows, so that the cable can be laid easily.
(8) After the cable is laid and the cable head is made, a DC withstand voltage leak test should be carried out according to the regulations before it is handed over to the operation management department and put into operation. After everything is qualified, it can be put into operation. When there is a problem with the cable during operation, it is necessary for the management personnel to strengthen the monitoring and deal with it in time. Once the cable fails, it will be very troublesome to deal with. It is necessary to find the fault point or even replace the entire cable. The system suffers from the impact of short-circuit current, causing unplanned power outages.
Therefore preventive testing before acceptance is essential. Of course, the DC withstand voltage test is a destructive test, which may have some influence on the life of the cable. Sometimes the cable test data is not ideal, but the cable can transmit power smoothly and run for a long time. Therefore, the new "Electric Power" In the "Equipment Preventive Test Regulations", it is no longer mandatory for the cross-linked cable to perform a DC withstand voltage test at a certain time interval, only the insulation resistance is measured, so the preventive test of the cable can be simplified. Accidents are also common.
When such an accident occurs, the cable insulation is severely damaged, and it can also cause water to enter the cable. Studies have shown that after the cable enters the water, under the action of the electric field, the phenomenon of water tree aging will occur, which will eventually lead to the breakdown of the cable. Water trees are collections of water-filled voids ranging from 0.1 m to several microns in diameter.
The impurities, pores in the insulation, and the local high electric field formed by the unevenness of the joint surface between the insulation and the inner and outer semiconducting layers are the starting points of the water tree. The development process of water tree is generally more than 8 years. The higher the humidity, temperature and voltage, the more ions contained in the water, the faster the water tree develops. The above is the specific solution to the damaged cable repair.
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