Capacitance Grading of cables||Grading of cables||Underground Cables

What is Grading of cables..Why it is required??
Grading of cables are done to uniformly distribute the dielectric Stress of the dielectric cable.
Dielectric stress is maximum at the surface of the conductor & minimum at the inner side of the surface which leads to insulation breakdown of the cable.Hence grading is necessary to maintain uniform stress across the cables.
There are two methods of grading of cables
1]Capacitance Grading
2}Inter Sheath Grading