Instrument transformer is the collective term for current transformers and voltage transformers. It can turn high voltage into low voltage and large current into small current for measurement or protection system. Its function is mainly to convert high voltage or large current into standard low voltage (100V) or standard low current (5A or 1A, both refer to the rated value) in proportion to realize the standardization and small size of measuring instruments, protection equipment and automatic control equipment. At the same time, Instrument transformer can also be used to isolate high-voltage systems to ensure the safety of people and equipment.

The structure of the current transformer is relatively simple, consisting of primary winding, secondary winding, iron core, frame, casing, and terminal that are insulated from each other.