I want my circuit to be isolated but I can't connect primary of transformer to grid because I can't afford 10Amps going through.

 

This module is based around the ZMPT101B precision voltage transformer and includes support circuitry. There is a lot of documentation on using it.

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The ZMPT107-1 may be useful: https://5nrorwxhmqqijik.leadongcdn.com/ZMPT107-1+specification-aidiqBqoKomRilSqqnnkikq.pdf

 

I can't connect primary of transformer to grid because I can't afford 10Amps going through.

A transformer pulls only a small magnetizing current (a few percent of the maximum load current) when it has no secondary load.