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

Here is Why You Need An Adapter

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

South Africa

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

Type C

Type M

Type N

Grenada

In Grenada, outlets of type G are in use.

Type G