Excessive heating of the cable will cause degradation of the insulation and sheathing material and premature failure.
Underground power cable failure.
The heat may come from an external source or may be generated by the resistance to current flow in the conductor a particular problem if the cable is overloaded and or underrated for the application.
Open circuits are usually the result of failed connectors or broken and or corroded conductors.
The paper insulation provided inside the cable is hygroscopic in nature.
The lead sheath is.
Sectionalizing this procedure as shown in fig.
Causes of faults in underground cables most of the faults occur when moisture enters the insulation.
Not all underground cable system failures are due to cable insulation.
Open circuits are more common in low voltage cables than at medium or high voltage.
Major causes are due to water ingress and poor workmanship.
Other causes include mechanical injury during transportation laying process or due to various stresses encountered by the cable during its working life.
1 risks reducing cable reliability because it depends on physically cutting and splicing the cable.
However the detection and localization of cable fault is challenging due to the limited access to the cable burned under the ground.
Heat shrink covers can be used to waterproof these junctions and improve reliability.
A substantial percentage occurs at splices terminations and joints.
There are two basic methods of locating an underground cable fault.