hello ,
you may use a current trasformer for isolation.The o/p can be fed to a Precision Rectfier (you better make it by using a fet i/p op. amp.like ca3130 or CA3140) the o/p of this precision rect. can be fed to a a to d converter, and the same can be given to the microcontroller.
If you need more detail information ,circuit etc,let me know.

r. s. saran