In underground cables, the electrostatic stress is ___ at contactor surface and ___ at the sheath.

• A. zero, minimum
• B. minimum, maximum
• C. zero, zero
• D. minimum, maximum

Answer: (D)

The electrostatic stress in a cable is not uniformly distributed.
The potential gradient is inversely proportional to the distance from the centre of the cable.
Hence, it will be maximum (gmax) at the surface of the conductor and goes on decreasing until it becomes minimum (gmin) 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.