Abstract: As the first line of defense for power grid safety, the technological development of relay protection is crucial for the stable operation of the power system. With the continuous expansion of the power grid scale and the increasingly complex operation mode, traditional relay protection faces severe challenges in dealing with cross regional faults and adapting to changes in system operation mode. To enhance the reliability of power grid protection, wide area relay protection technology has emerged. The article explores the technical characteristics of wide area relay protection in terms of information domain division methods, protection system structure classification, and fault discrimination algorithms, aiming to provide a new technical path for building a protection system that meets the needs of modern power grids.