Study on data transmission of RTDMS for power systems

Real Time Dynamic Measure System (RTDMS) is widely used in China, which is also called Wide Area Monitoring System (WAMS) or Wide Area Monitoring Analysis Protection-control (WARMAP). Now the infrastructure of power optical fiber communication networks is mainly based on Synchronous Digital Hierarchy (SDH)/Synchronous Optical Network (SONET) in China. In the future, Optical Transport Network (OTN) will be a new generation data transmission technology, its operability, flexibility, reliability, and ease of management are better than SDH and SONET, and it will be used in Chinese state grid system and provide extra large capacity bandwidth and directly dispatch large-granule services. The paper analyses and studies the communication requirements of RTDMS. Phasor Measurement Unit (PMU) devices, based on the synchronized measurement technology, are basic building blocks of RTDMS, which is Similar to the Remote Terminal Unit (RTU) in Energy Management System (EMS). Between the PMU and the master station of RTDMS, One investigation about the shortage of the electric power communication network for RTDMS is given out. One solution is put forward in this paper, which includes the infrastructure of communication subsystem, the configuration of RTDMS, communication protocols and so on. The communication subsystem is based on wide area network. So it is complicated for PMU and main station of RTDMS to connect with wide area network, one mode is provided in this paper. In RTDMS, one very large special database is used to store the data collected from the fields, one special transmission protocol is used to organize the data frame for data delivering. The architecture of data transmission protocol, principal contents, requirements of RTDMS, data flowing scheme, and data frame format are presented in this paper. The protocol is widely applied in grids of every voltage level in China. In order to regularize the connection between main station of RTDMS and PMUs, a Chinese standard - n communication "Real-time dynamic monitoring systems of power system Part 2: Protocols for data transferring" was devised in 2008, which is introduced in this paper too. It defined real time data frame, command frame, head frame, configuration frame, and offline data frame in main context. Six annexes were added into the standard. Annex A,B, and C defined the process of data transferring. Annex D and E defined the rules for naming in RTDMS. Annex F defined CRC16 program code. To improve communication efficiency of RTDMS, other efforts are also underway.