What Are The Causes Of Cable Failures?

The most direct cause of cable failure is the breakdown of insulation due to degradation.

There are many factors that reduce the thermal conductivity and insulation. According to the actual operation experience, it can be summed up in the following situations.

1. External force damage.

According to the operation analysis in recent years, especially in Shanghai Pudong, which is developing at a high speed, a considerable number of cable faults are now caused by mechanical damage.

For example, non-standard construction during cable laying and installation is easy to cause mechanical damage; civil construction on directly buried cables is also very easy to damage the cables in operation. Sometimes if the injury is not serious,

It will take several months or even several years for the damaged part to break down completely to form a fault, and sometimes a short-circuit fault may occur if the damage is serious, which directly affects the safe production of electricity units.

2. The insulation is damp.

This situation is also very common and usually occurs at cable joints in direct burial or in pipes. For example, if the cable joints are unqualified and the joints are made under humid climate conditions, the joints will enter water or be mixed with water vapor. After a long time, water branches will form under the action of the electric field, which will gradually damage the insulation strength of the cables and cause failures.

3. Chemical corrosion.

The cable is buried directly in the area with acid and alkali effect, which often causes the armor, lead or outer sheath of the cable to be corroded. The protective layer has been subjected to chemical corrosion or electrolytic corrosion for a long time, resulting in the failure of the protective layer and the reduction of insulation, which will also lead to Cable failure.

4. Long-term overload operation.

In overload operation, due to the thermal effect of the current, the conductor will heat up when the load current passes through the cable. At the same time, the skin effect of the electric charge, the eddy current loss of the steel armor, and the loss of the insulating medium will also generate additional heat, which will increase the temperature of the cable. During long-term overload operation, excessive temperature will accelerate the aging of the insulation, and even the insulation will be broken down. Especially in hot summer, the temperature rise of the cable often causes the weak part of the cable insulation to be broken down first, so in summer, there are many cable failures.

5. The cable connector is faulty.

The cable joint is the weakest link in the cable line, and the cable joint failure caused by the direct fault of the personnel (poor construction) often occurs. In the process of making cable joints, if there are original nets such as joints that are not crimped tightly, insufficient heating, etc., the insulation of the cable head will be reduced, resulting in accidents.

6. 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.

7. Other reasons such as normal aging of the cable body or natural disasters.