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

Here is Why You Need An Adapter

The outlet and plug type used in Norfolk Island is I 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

Norfolk Island

In Norfolk Island, outlets of type I are in use.

Type I