Square through type residual current transformer is mainly used in cable circuit environment. It has simple structure, small volume and flexible application. According to specifications of the cable used in the main circuit, there are various through hole diameter. The through hole diameter of this series of products ranges from 100mm to 450mm, and the main circuit current includes 63A ~ 2000A. This series of products can meet the technical requirements of 0.2 level, 0.5 level and 1 level and other difference 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, or even 3mA, greatly reducing the false alarm caused by the magnetic field interference 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.