a)How do voids in the insulation cause breakdown of the cable? b)How do the various devices protect the penstock?
a)How do voids in the insulation cause breakdown of the cable?
b)How do the various devices protect the penstock?
High voltage cables are used for the transmission and distribution purpose for electric power. In high voltage cables, the main reason for the breakdown is partial discharge due to the voids inside the insulation which shortens the life of cable.
Electrostatic stress varies due to the presence of void inside the insulation material. The stress distribution in the insulation containing a void is influenced by the size of the void, shape of the void, location of the void, dielectric permittivity of insulation material and operating voltage.
If the The electric field and stress inside the void is higher so the possibility of breakdown increases.
The maximum void stress (Emax) decreases with increasing the distance of the void center from the conductor surface. Void stress is stronger with the void nearer to the conductor surface and if the void is far away from the conductor surface the maximum void stress will be less.
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