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Cause classification of power cable faults
- May 18, 2017 -

The breakdown of underground power cable is complex and changeable, and causes the breakdown of power cable can be summarized into the following categories.

1. Mechanical damage
The cable fault caused by mechanical damage occupies a large proportion of the cable accident. Some mechanical injuries are minor, which did not cause a malfunction, and the damage was developed in a few months or even years. The main causes of mechanical damage to cables are:
(1) damage during installation. Accidentally bump the cable during installation; mechanical traction over large tensile cable; excessive bending cable.
(2) Direct acceptance of external damage. After the installation of the cable path or near the civil construction, so that the cable directly affected by external damage.
(3) The vibration or impact load of the driving vehicle will also cause the lead (aluminium) crack loss of the underground cable.
(4) Damage caused by natural phenomena. such as intermediate joint or terminal head of internal insulating rubber swelling and cracking casing or cable sheath; The cable jacket is scratched on the nozzle or the bracket, and the intermediate joints or conductors are pulled by the land subsidence caused by excessive pulling force.

2. Damp insulation
The insulation will cause the breakdown of the cable pressure drop after damp. The main reasons for damp cables are:
(1) Because the connector box or terminal box structure is not sealed or improper installation results in water.
(2) Poor cable manufacturing, metal sheath has small holes or cracks.
(3) Metal sheath is stabbed or corroded by exterior.

3. Insulation aging Deterioration
Insulation aging can cause the cable pressure drop and malfunction. The main reasons for the ageing of cables are:
(1) The slag or air gap inside the cable medium produces free and hydrolysis under the electric field.
(2) The cable overload or the cable communication wind is bad, causing local overheating.
(3) The insulating material of the oil-immersed paper cable is lost.
(4) Power cable ultra-time use.

4. Overvoltage
Overvoltage causes the defective cable insulation layer to wear electric shocks, causing the cable failure. The main reasons are: atmospheric overvoltage (e.g. lightning strikes), internal overvoltage (e.g. operating overvoltage).

5. Poorly designed and manufactured craft
Cable head and intermediate design and production process is bad, also can cause cable malfunction. The main reasons are: The distribution of electric field is poorly designed, material selection is inappropriate, poor workmanship, not according to the requirements of the production procedures.