Power equipment is divided into primary equipment and secondary equipment. Primary equipment refers to the equipment that directly undertakes the functions of power generation, transmission, transformation, distribution, and electricity consumption. Secondary equipment refers to various equipment required for the normal operation of primary equipment and the realization of power management goals, such as generator set protection and dispatch automation systems.

The technical development of relay protection is inseparable from the development of electronics, information, communication and other technologies. In the future, with the gradual application of electronic CT (current transformer) and PT (voltage transformer), and the further improvement of the IEC61850 standardization protocol, it is foreseeable that digital technology will be more widely used.
The development of power grid equipment and operation control technology, such as the research of digital substations, the application of unattended substations, the construction and operation of UHV power grids, etc., will put forward higher requirements for the performance of relay protection technology, and it is necessary to study and propose new relays protection solutions. The actual operation of the power grid and the lessons of power grid accidents at home and abroad show that the failure of a single relay protection device or a single component of the device may lead to a power grid accident, and it is still necessary to further improve the reliability of the relay protection equipment.