This paper provides a comprehensive review of the key applications and technological evolution of communication technologies in the field of relay protection in recent years, with a focus on the integration patterns and performance characteristics of optical fiber communication . This paper provides a comprehensive review of the key applications and technological evolution of communication technologies in the field of relay protection in recent years, with a focus on the integration patterns and performance characteristics of optical fiber communication . Relay protection systems are essential in maintaining the safety and reliability of modern electrical grids. As technology advances and grids become smarter, the tools used to test and maintain these systems, such as the relay test set, are evolving to meet new challenges. This article explores the. The global energy transition is ushering in a new era of power electronic-dominated grids (PEDGs), to complement the increase in the widespread integration of renewable sources like wind and solar. Relay protection technology plays a vital role in fault detection, isolation, and recovery, evolving with intelligent algorithms, digital equipment, and automated coordination to enhance grid reliability. This paper explores the development of relay protection technology in smart grids, analyzing.