The method of creating uniform electrostatic stress in the dielectric of underground cables is known as ______ of cables.

Grading of cable:

• The electrostatic stress in a cable isn’t uniformly distributed. The potential gradient is inversely proportional to the distance from the center of the cable. Hence it will be maximum (g_max) at the surface of the conductor and goes on decreasing until it becomes minimum (g_min) at the surface of the sheath.
• That means electrostatic stress in the dielectric of a cable is maximum at the surface of the conductor and minimum at the surface of the sheath.
• Obviously, for a safe cable, the dielectric strength of the insulation provided must be more than g_max i.e. maximum value of the potential gradient. As the electrostatic stress in a cable isn’t uniformly distributed, the strength of the dielectric required isn’t uniform either.
• The maximum dielectric strength is required only at the surface of the core. The remaining dielectric is unnecessarily strong and hence not utilized properly. This also causes the cable to be unnecessarily thick. 
• A large size of electric equipment is always a disadvantage. Furthermore, the possibility of insulation breakdown is greater if the stress distribution is non-uniform. These problems are rectified by Grading the cables.
• The process of achieving uniform electrostatic stress in the dielectric of cable is known as the grading of cables. 
• The following are the two main methods of grading of cables: Capacitance grading and inter-sheath grading.