Isolation Transformer:

Isolation transformers are generally low power transformers used to isolate noise from or to ground electronic circuits. Because a transformer cannot pass DC voltage from primary to secondary, any DC voltage like as noise cannot be passed or the transformer acts to isolate this noise.

Instrument Potential Transformer:

The instrument potential transformer (PT) steps down voltage of a circuit to a low value that can be effectively and safely used for operation of instruments such as ammeters, watt meters, voltmeters, and relays used for various protective motives.