Views:94 Author:Site Editor Publish Time: 2019-09-16 Origin:Site
We can see earthing device everywhere, but we don't pay much attention to them. In fact, grounding system has a great deal to do with us. We must pay attention to the wires and electric cables around us. Earthing electrode are exposed to natural or artificial environment for a long time, and they are easy to produce aging with the passage of time. At the same time, earth cable aging may not only cause fire, electric shock hazards, but also affect the service life of various electrical appliances.
Cable joint is the weakest link in cable line. Cable joint faults caused by direct negligence (poor construction) often occur. During the process of making the cable joints, if the joints are not tightly pressed or insufficiently heated, the insulation of the cable heads will be reduced, causing an accident.
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.
This situation is very common, usually occurs at cable joints in direct buried or drained pipes. For example, unqualified cable joints made in wet weather conditions will make the joints into water or vapor. Water droplets will form under the action of the electric field for a long time, which will gradually damage the insulation strength of the cable and cause malfunction.
Cables buried directly in areas with acid-base effect often cause corrosion of armor, lead or outer shield of cables. The protective layer suffers from chemical or electrolytic corrosion for a long time, which leads to failure of the protective layer and reduction of insulation, and also leads to cable failure.
Due to the thermal effect of current, when the load current passes through the cable, overload operation will inevitably lead to conductor heating. At the same time, skin effect of charge, eddy current loss of steel armor and dielectric loss will also produce additional heat, which will increase the temperature of the cable. During long-term overload operation, excessive temperature will accelerate the aging of insulation and the insulation will be broken down. Especially in the hot summer, the temperature rise of cable often leads to the first breakdown of the weak insulation of cable. So in the summer, there are more cable faults.
Judging from the operational analysis in recent years, especially at where the economy is developing at a high speed, quite a number of cable faults are now caused by mechanical damage. For example, when the cable is laid and installed, the construction is not standardized, which is easy to cause mechanical damage. Civil construction on directly buried cables is also very easy to cause cable damage in operation. Sometimes if the damage is not serious, it will take several months or even years to cause the damage parts to break down completely and form a fault. Sometimes serious damage may occur short-circuit fault, which directly affects the safe production of the power unit.
Common faults of cable lines include mechanical damage, insulation damage, insulation damp, insulation aging, over-voltage, cable overheating and so on. When the above-mentioned faults occur, the power supply of the faulty cable should be cut off, the fault point should be found, the fault should be checked and analyzed, and then repaired and tested. The power supply can be restored only after the fault is eliminated.
After understanding the cause of cable aging, I hope that everyone can deal with the aging grounding wires in time to avoid fire accidents.