You Do Need power plug adapter while traveling from Grenada to South Africa.

Here is Why You Need An Adapter

The outlet and plug type used in South Africa are C, M and N and in Grenada is G. This is how they look like.

Grenada

In Grenada, outlets of type G are in use.

Type G

South Africa

In South Africa, outlets of type C, M and N are in use.

Type C

Type M

Type N