You Do Need power plug adapter while traveling from Oman to South Sudan.

Here is Why You Need An Adapter

The outlet and plug type used in South Sudan are C and D and in Oman is G. This is how they look like.

Oman

In Oman, outlets of type G are in use.

Type G

South Sudan

In South Sudan, outlets of type C and D are in use.

Type C

Type D