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Analysis of the causes of wire and cable aging and the disadvantages of cable aging

Date:2018/4/28 15:33:32

What are the general causes of cable aging? The most direct cause of wire and cable aging failures is insulation breakdown and breakdown. Many factors reduce the sensitivity of insulation. Based on the actual operating experience, it can be summarized as the following conditions.


   1) The cause of cable aging: external force damage. Judging from the operation analysis in recent years, especially in Haipudong, where the economy is developing rapidly, a considerable number of cable faults are now caused by mechanical damage. For example: when the cable is laid and installed, the construction is not standardized, and it is easy to cause mechanical damage; it is also very easy to damage the running cable during civil construction on directly buried cables. l Sometimes if the damage is not serious, it will take months or even years to cause the damage to the complete breakdown of the damaged part to form failure, and sometimes the serious damage may cause a short-circuit failure, which directly affects the safe production of the electric unit and the power user unit.


   2) Cause of cable aging: the insulation is damp. This situation is also very common, and generally occurs at the cable joints in direct buried or drain pipes. For example, unqualified cable joints and making joints under humid climate conditions will cause water or steam to enter the joints. For a long time, water branches will form under the action of the electric field, which will gradually damage the insulation strength of the cable and cause failure.


   3) The cause of cable aging: chemical corrosion. The cable is directly buried in the area with acid and alkali effects, which often causes the armor, lead skin or outer sheath of the cable to be corroded. The protective layer is subjected to chemical corrosion or electrolytic corrosion for a long time, failing the protective layer and the reduction in insulation. The cable is faulty. Chemical: the unit's cable corrosion is quite serious


   4) Cause of cable aging: long-term overload operation. Overload operation, due to the thermal effect of the current, when the load current passes through the cable, the conductor will inevitably heat. At the same time, the skin effect of the charge, the eddy current loss of the steel armor, and the dielectric loss will also produce additional heat, which will increase the temperature of the cable. During long-term overload operation, excessively high temperatures will accelerate the aging of the insulation, so that the insulation is broken. Especially in the hot summer, the temperature rise of the cable often causes the weak insulation of the cable to be broken down first, so in the summer, there are especially many cable failures.


   5) The cause of cable aging: cable connector failure. The cable connector is the weakest link in the cable route, and the cable connector failure caused by a direct fault (poor construction) of the personnel often occurs. In the process of making cable joints, if the original network of the joints is not tightly pressed or the heating is insufficient, the insulation of the cable head will be reduced, which will lead to accidents.


   6) Causes of cable aging: environment and temperature. The external environment and heat source of the cable will also cause the cable temperature to be too high, insulation breakdown, and even explosion and fire.


  How to judge the wire aging

   1. Whether there is current leakage or even short circuit and fire;


   2. The insulation skin is hardened and cracked;


   3. The contact resistance increases and the joint becomes hot.


   List the causes of cable aging mainly as follows:


   1. Long-term overload operation. Overload operation, due to the thermal effect of the current, when the load current passes through the cable, the conductor will inevitably heat. At the same time, the skin effect of the charge, the eddy current loss of the steel armor, and the dielectric loss will also produce additional heat, which will increase the temperature of the cable.


   2. Environment and temperature. The external environment and heat source of the cable will also cause the cable temperature to be too high, insulation breakdown, and even explosion and fire.


   3. External force damage. Judging from the operation analysis in recent years, a considerable number of cable failures are caused by mechanical damage.


   4. Insulation moisture. It usually occurs at the cable joints in direct buried or drains pipes. It took a long time to form water branches under the action of the electric field, gradually damaging the insulation strength of the cable and causing failure.


   5. The cable connector is faulty. The cable connector is the weakest link in the cable route, and the cable connector failure caused by a direct fault (poor construction) of the personnel often occurs.


   6. Chemical corrosion. The cable is directly buried in the area with acid and alkali effects, which

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