1. Mechanical damage Power cable failures caused by mechanical damage account for a large proportion of cable accidents. Some mechanical damages were very minor, and did not cause failure at that time, but the damaged parts did not develop into failure until several months or even years later.
1. Mechanical damage
Power cable failures caused by mechanical damage account for a large proportion of cable accidents. Some mechanical damages were very minor, and did not cause failure at that time, but the damaged parts did not develop into failure until several months or even years later.
2. Damage during installation
The cable is accidentally damaged during installation, the cable is pulled due to excessive mechanical traction, or the cable is damaged due to excessive bending.
3. Damaged by direct external force
After installation, urban construction is carried out on or near the power cable path, causing direct external force damage to the power cable; The vibration or impact load of running vehicles will cause the lead (aluminum) package crack of underground cables.
4. Insulation damped
The insulation is affected with moisture and causes failure. The main causes of power cable being affected with damp are: water ingress due to unsealed structure or poor installation of connector box or terminal box; The cable is poorly manufactured, and the metal sheath has holes or cracks; The metal sheath is punctured or corroded by foreign objects.
5. Aging and deterioration of insulation
The air gap inside the insulating medium of power cable will become free under the action of electric field, which will make the insulation decline. When the insulating medium is ionized, ozone, nitric acid and other compounds will be generated in the air gap, which will corrode the insulation; The moisture in the insulation will hydrolyze the insulating fiber and cause the insulation to decline. Overheating will cause aging and deterioration of insulation. The electric dissociation generated in the air gap inside the power cable causes local overheating and carbonizes the insulation.