Isolation Transformer

An Isolation Transformer is used to transfer electrical power from a source of alternating current (AC) to some equipment or device while Galvanically isolating the powered device from the power source, usually for safety reasons.
While Transformer are usually used to change voltages, isolation Transformer with a 1:1 ratio are used in safety applications.
Galvanic isolation is used where two or more electric circuits must communicate, but their grounds may be at different potentials. Galvanic isolation is a design technique that separates electrical circuits to eliminate stray currents. Signals can pass between Galvanically isolated circuits, but stray currents, such as differences in ground potential or currents induced by AC power, are blocked.
It is an effective method of breaking ground loops by preventing unwanted current from flowing between two units sharing a ground conductor. Galvanic isolation is also used for safety, preventing accidental current from reaching ground through a person's body.
If two electronic systems have a common ground, they are not Galvanically isolated. The common ground might not normally or intentionally have connection to functional poles, but might become connected. For this reason isolation Transformer do not supply a GND/earth pole.