XJ has consecutively overcome a series of world-class technical challenges in UHV AC protection research and production, including transient capacitive current identification in UHV AC, precise double-end fault location on transmission lines, and automatic identification of inter-turn faults in shunt reactors. It has fully mastered the key technologies of 1000kV AC transmission systems. The project titled "Key Technologies, Complete Equipment, and Engineering Applications for Ultra-high Voltage AC Transmission" was awarded the National Science and Technology Progress Special Prize.