Friday, September 2, 2011

Difficulties in Grading

       In the intersheath grading, the intersheath has to be thin. Hence there is possibility of damage to it while laying the cable. Similarly intersheath has to carry the charging current which can cause overheating of cable.
       In capacitance grading, to have uniform distribution of stress it is necessary to select the dielectrics of proper permittivities. But practically it i difficult to get the proper values of permittivities. But practically it is difficult to get the proper values of permittivities. Similarly the permittivity of dielectric changes with the time which can cause uneven distribution of stress. Such uneven distribution may lead to breakdown at the normal operating voltage.
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