Power cables can be divided into low resistance grounding or short circuit faults, high resistance grounding or short circuit faults, broken wire faults, broken wire and ground faults, and flashover faults based on the nature of the faults
Analysis of the causes of cable faults. The common main reasons are summarized as follows
1. Mechanical damage
Cable faults caused by mechanical damage account for a large proportion of cable accidents.
. Some mechanical damages are minor and did not cause a malfunction at the time, but it took several months or even years for the damaged area to develop into a malfunctionThere are several main reasons for mechanical damage to cables during installation
Damage during installation: accidentally hitting the cable during installation, pulling the cable due to excessive mechanical traction, or damaging the cable due to excessive bending Direct external force damage: Urban construction is carried out on or near the cable path after installation, causing direct external force damage to the cable; The vibration or impact load of driving vehicles can cause lead (aluminum) cladding damage to underground cables
2. Damping of insulation
Causes faults after insulation is damp.
. The main reasons for cable moisture include: water ingress due to unsealed or poorly installed joint or terminal box structures; Poor cable manufacturing, small holes or cracks in the metal sheath; The metal sheath is punctured or corroded by external objects3. Insulation aging and deterioration
The internal air gap of the cable insulation medium generates dissociation under the action of an electric field, causing insulation degradation.
. When the insulation medium ionizes, ozone, nitric acid, and other chemical compounds are generated in the air gap, which corrodes the insulation; The moisture in the insulation causes hydrolysis of the insulation fibers, resulting in a decrease in insulation. Overheating can cause insulation aging and deterioration. The internal air gap of the cable generates electrical dissociation, causing local overheating and carbonization of the insulationFunction of testing report:
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