A zero sequence current transformer for measuring leakage current in cable lines. This product boasts a simple structure and is versatile in application. It offers multiple core hole sizes to accommodate the cable specifications used in the main circuit, with the main circuit current ranging from 63A to 2000A. It also meets the requirements for balanced characteristics, delivering an unbalanced current output superior to 30mA, 10mA, and 5mA. Made with high-quality high-conductivity magnetic cores and utilizing advanced manufacturing processes, it can satisfy technical requirements across various precision levels, including Class 0.2, Class 0.5, and Class 1.0, ensuring high reliability. It is used in motor protection, electromagnetic relay protection devices, and microcomputer protection devices; electrical fire monitoring, fire leakage protection systems, and low-current grounding systems. The zero sequence current transformer is a crucial device in the power system. It operates based on the principle of electromagnetic induction and detects zero sequence current to achieve protection and monitoring of the power system, providing vital guarantees for its safe and stable operation.