Analysis of Several Causes of Aging of Electric Wires and Cables

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2021-10-07 17:51

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　　Analysis of Several Causes of Aging of Electric Wires and Cables
The most direct cause of aging faults in wires and cables is breakdown due to reduced insulation. There are many factors contributing to the reduction of conductive insulation, and based on actual operating experience, it can be summarized as the following situations.
Several reasons for cable aging
1) Reason for cable aging: external force damage. From the operational analysis in recent years, especially in the rapidly developing economy 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; Conducting civil construction on directly buried cables can also easily damage cables during operation. Sometimes, if the damage is not severe, it may take several months or even years to cause complete breakdown of the damaged area and form a fault. Sometimes, if the damage is severe, a short circuit fault may occur, directly affecting the safety production of the electricity company and the electricity consuming unit.
Analysis of Several Reasons for Aging of Electric Wires and Cables
2) Reason for cable aging: Damping of insulation. This situation is also very common, usually occurring at the cable joints in directly buried or lined pipes. For example, unqualified cable joints and joints made in humid weather conditions can cause water or steam to enter the joints. Over time, water branches will form under the action of the electric field, gradually damaging the insulation strength of the cable and causing faults.
3) Reason for cable aging: chemical corrosion. Directly burying cables in areas with acid-base effects often leads to corrosion of the cable's armor, lead skin, or outer protective layer. The protective layer may become ineffective due to long-term chemical or electrolytic corrosion, resulting in reduced insulation and cable failure. Chemical: The corrosion of cables in the unit is quite severe
4) Reason for cable aging: long-term overload operation. Overload operation, due to the thermal effect of the current, when the load current passes through the cable, it will inevitably lead to conductor heating. At the same time, the Skin effect of the charge, the eddy current loss of the steel armor, and the insulation medium loss will also produce additional heat, which will increase the cable temperature. During long-term overload operation, excessively high temperatures can accelerate insulation aging, leading to insulation breakdown. Especially in hot summer, the temperature rise of cables often leads to the first breakdown of weak insulation areas, so there are particularly many cable faults in summer.
5) Reason for cable aging: cable joint failure. Cable joints are the weakest link in cable routes, and cable joint failures often occur due to personnel's direct negligence (poor construction). During the production of cable joints by construction personnel, if there are loose crimping or insufficient heating of the joints in the original network, it will lead to a decrease in the insulation of the cable head, leading to accidents.
6) Reasons for cable aging: environment and temperature. The external environment and heat source in which the cable is located can also cause excessive temperature, insulation breakdown, and even explosion and fire.
Classification of wires and cables
Bare wire body products
The main features of this type of products are: pure conductor metal, without insulation and sheath layer, such as steel cored aluminum strand, copper aluminum bus bar, Electric locomotive line, etc; The processing technology mainly involves pressure processing, such as melting, rolling, drawing, stranding/compression stranding, etc; The product is mainly used in suburban areas, rural areas, user mainlines, switchgear, etc.
Analysis of Several Reasons for Aging of Electric Wires and Cables
power cable
The main characteristics of this type of product are: extruding (winding) an insulation layer outside the conductor, such as overhead insulated cables, or twisting several cores (corresponding to the phase, zero, and ground wires of the power system), such as overhead insulated cables with two or more cores, or adding a protective layer, such as plastic/rubber sheathed wires and cables. The main process technologies include drawing, stranding, insulation extrusion (wrapping), cable forming, armor and sheath extrusion, etc. The different process combinations of various products have certain differences.
The product is mainly used for the transmission of strong electrical energy in power generation, distribution, transmission, transformation, and power supply lines, with high current (tens to thousands of amperes) and high voltage (220V to 35kV and above).
The main characteristics of this kind of products are: a wide range of varieties and specifications, a wide range of applications, a large number of use voltages of 1kV and below, and constantly deriving new products in the face of special occasions, such as fire-resistant cables, flame retardant cables, Low smoke zero halogen/low smoke low halogen cables, termite resistant, rat resistant cables, oil resistant/cold resistant/temperature resistant/wear-resistant cables, medical/agricultural/mining cables, thin wall wires, etc.
Communication cables and optical fibers
With the rapid development of the communication industry, from simple telephone and telegraph cables in the past to thousands of pairs of telephone cables, coaxial cables, optical cables, data cables, and even combined communication cables. This type of product usually has small and uniform structural dimensions, and requires high manufacturing accuracy.

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List of main types of wires and cables

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List of main types of wires and cables