Circular through type current transformer is mainly used in cable circuit environment. It has simple structure, small volume and flexible application. According to the cable specifications of cable used in the main circuit, there are a variety of through hole diameters. The through hole diameter of this series of products ranges from 30mm to 200mm, and the main circuit current includes 63A ~ 2000A. The series of products can meet the technical requirements of 0.2 level, 05level, 1level and other different precision. At the same time, it can also meet the strict requirements of the new national standard for the balance characteristics. The unbalanced current output value can also be better than 30mA, 10mA, 5mA, even 3mA, greatly reducing the false alarm caused by the magnetic field of the main circuit current, providing sufficient guarantee for the reliability of the equipment. Excellent and advanced production process. This series of products meet the requirements of GB-14287.2-2005 and GB14287.2-2014.