Communication test and analysis of integrated protection system in digital substation

The development of digital substation provides new opportunity for integrated protection. However, the realization of integrated protection is constrained by serial communication between process level and bay level. Based on developed digital integrated protection and control system platform, the result of a physical simulation test concerning communication system reveals the problem of communication instability and packet loss. In this paper, the impact of GPS exerted on stability of integrated protection is tested and analyzed. Without GPS time setting of Merging Unit (MU) in different bay, the integrated protection system will lose data in one minute after running. With GPS, the communication is stable and reliable, but the time interval between two packets in a cycle is quite long. Since sampling of MU in different bay is synchronized by GPS, the availability of integrated protection system is directly affected by communication of integrated protection in digital substation.