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Analysis of Several Reasons for the Aging of Wires and Cables

Industry news
2021/10/07 17:07

Analysis of Several Reasons for the Aging of Wires and Cables
  The most direct cause of the aging failure of the wire and cable is the breakdown of the insulation due to degradation. There are many factors that lead to sensitive insulation degradation. According to actual operating experience, it can be summed up in the following situations.
   Several reasons for cable aging
   1) Reasons for cable aging: external force damage. Judging from the operation analysis in recent years, especially in the high-speed economic development of Haipudong, a considerable number of cable failures are now caused by mechanical damage. For example, non-standard construction during cable laying and installation can easily cause mechanical damage; civil construction on directly buried cables can also easily damage cables in operation. l Sometimes if the damage is not serious, it will take months or even years to cause the damaged part to be completely broken down and form a fault. Sometimes a short-circuit fault may occur if the damage is serious, which directly affects the safe production of the electric power and the power user.
  Analysis of several reasons for the aging of wires and cables
   2) Reasons for cable aging: insulation is damp. This situation is also very common, and generally occurs at the cable joints in direct burial or piping. For example: unqualified cable joints and joints made in humid weather conditions will cause the joints to enter water or water vapor. For a long time, water branches will be formed under the action of the electric field, which will gradually damage the insulation strength of the cable and cause failure.
  3) Reasons for cable aging: chemical corrosion. The cable is directly buried in the area with acid and alkali, which will often cause the cable armor, lead skin or outer sheath to be corroded. The protective layer suffers from chemical corrosion or electrolytic corrosion for a long time, resulting in the failure of the protective layer and the reduction of insulation. The cable is faulty. Chemical: the unit’s cable corrosion situation is quite serious
  4) Reasons for cable aging: long-term overload operation. Overload operation, due to the thermal effect of the current, the conductor heating will inevitably be caused when the load current passes through the cable. At the same time, the skin effect of the charge, the eddy current loss of the steel armor, and the insulation loss will also generate additional heat, which will increase the temperature of the cable. During long-term overload operation, the excessively high temperature will accelerate the aging of the insulation, and even the insulation will be broken down. Especially in the hot summer, the temperature rise of the cable often leads to the first breakdown of the weak insulation of the cable, so in the summer, there are more cable faults.
  5) Reasons for cable aging: cable connector failure. The cable joint is the weakest link in the cable line, and the cable joint failures caused by the direct fault of the personnel (poor construction) often occur. In the process of making cable joints, if there are original nets such as insufficient joint crimping, insufficient heating, etc., the insulation of the cable head will be reduced, which will cause an accident.
  6) Reasons for cable aging: environment and temperature. The external environment and heat source of the cable can also cause the cable to overheat, insulation breakdown, and even explosion and fire.
  Wire and cable classification
   Bare Wire Body Products
The main features of this category of products are: pure conductive metal, no insulation and sheath, such as steel core aluminum stranded wire, copper-aluminum busbar, electric locomotive wire, etc.; the processing technology is mainly pressure processing, such as smelting, rolling, drawing The products are mainly used in suburbs, rural areas, user main lines, switch cabinets, etc.
  Analysis of several reasons for the aging of wires and cables
  power cable
The main features of this type of product are: squeeze (wind) the insulation layer outside the conductor, such as overhead insulated cables, or stranded several cores (corresponding to the phase wires, neutral wires and ground wires of the power system), such as overhead insulated cables with more than two cores , Or add a sheath layer, such as plastic/rubber sheathed wire and cable. The main process technologies include drawing, stranding, insulation extrusion (wrapping), cable formation, armoring and sheath extrusion, etc. The different process combinations of various products have certain differences.
  The products are mainly used in the transmission of strong electric energy in power generation, distribution, transmission, transformation, and power supply lines. The current passing through is large (tens of amperes to several thousand amperes) and high voltage (220V to 35kV and above).
The main features of this type of products are: a wide range of varieties and specifications, a wide range of applications, and the use of more voltages of 1kV and below. In the face of special occasions, new products are continuously derived, such as fire-resistant cables, flame-retardant cables, low-smoke and halogen-free/low Smoke and low halogen cables, termite-proof, mouse-proof cables, oil/cold/temperature/wear-resistant cables, medical/agricultural/mining cables, thin-walled cables, etc.
  Communication cable and optical fiber
  With the rapid development of the communication industry, the simple telephone and telegraph cables have developed from the past to thousands of pairs of telephone cables, coaxial cables, optical cables, data cables, and even combined communication cables. The structure size of this kind of products is usually small and uniform, and the manufacturing precision is high.

Analysis of Several Reasons for the Aging of Wires and Cables