Analysis Of Power Cable Faults

- May 12, 2018-

The causes of power cable faults are as follows:

    Insulation aging deterioration:

    Power cable insulation is subject to thermal, chemical, and mechanical effects that are accompanied by electrical effects, which causes physical and chemical changes in the insulation medium, which degrades the insulation level of the medium. Insulation is damp. Intermediate joints or terminal heads cause insulation and dampness due to poor sealing of the structure or poor installation quality; defects such as blisters or cracks are left in the manufacture of lead-bundle cables, which can also make cables wet.

Cable overheating:


    There are many reasons for overheating the cable. The internal cause is local heating of the air gap inside the cable insulation, which in turn causes the insulation to char. External factors are cables installed in dense cable areas, cable tunnels, etc. Cables that are put in dry pipes and cables that are close to the pipes can cause accelerated insulation damage due to cable overload or poor heat dissipation.

mechanical injury:


    Mainly refers to the cable damage caused by external forces. This is mainly due to mechanical action such as vibration of the vehicle and deformation of the cable. Deformation of the cable results in excessive bending, damage to the inner insulation or an air gap inside the insulation.

Cover corrosion:

    Due to the electrolysis or chemical effects of lead corrosion of the cable, due to the different nature and degree of corrosion, the lead package has red, yellow, orange and yellowish compounds or pores resembling sponges.

Overvoltage causes breakdown:


    Atmospheric over-voltage and internal over-voltage cause the insulation of the cable to exceed the allowable stress to cause breakdown.

Moreover, analysis of actual faults indicates that many outdoor terminal head faults are caused by atmospheric over-voltage.

The design of intermediate joints and terminal heads and the manufacturing process problems:


    When semiconductors are stripped, damaged internal insulation or insulating surfaces have particles, dust, and other impurities; poor sealing of the cable heads causes moisture inside the insulation, resulting in moisture and moisture; cable connector technology is not standard, sealing is not standardized, resulting in grounding; production environment humidity is large Causes the insulation integrity of the production site (cable head); the grounding of the cable is incorrect, causing the ground wire to form a current or break.

For the above seven types of faults in power cables, measures can be formulated in combination with the actual situation. For the production process of the intermediate joints and the terminal heads, it is possible to strengthen the test of the attachments of the cable entry heads and strictly check on the basis of the implementation of the relevant regulations; when peeling the jackets and insulating layer semiconductor layers carefully, the insulating surfaces are thoroughly ground and cleaned. Prevent foreign particles from remaining on the insulation; the humidity of the installation environment is kept below 70%. A series of clear provisions have been made for the installation of cables: the armor layer and the copper shield must be grounded separately and their cross-section is not less than 25 mm2; single-core cables must be grounded at one end of the power receiving end, and the three-core cable must be grounded at both ends. The tin wire should be tinned. In order to prevent the cable from being damaged due to external forces, the force part can be protected by pipe protection and fixed. The middle joint is protected from the outside and the joints are fixed on both sides. During the construction process, the thread nose is not twisted and deformed by external forces. If necessary, To handle twisting, measures should be taken to make the surface smooth; when construction teams are near the cable, notices should be added and personnel must be reminded when necessary.