The Research And Application Of Data Relay Based On GPRS Communications Technology

This paper studies the application of GPRS technology used in the substation monitoring system. The works are mainly on developing data relay of GPRS DTU equipment which uses the CDT protocol as its communication protocol. For the various substations distribution is disperse, and the distance between the monitoring master system and various substations is very far, hence using GPRS communications technology can reduce the cost of wiring. In order to keep the monitoring system in a stable communication channel, the project adopts the solution of Internet static IP address. Because of the limitation of monitoring master station, we can not apply static IP address, so we put a server at the IDC room of China Telecom, and then apply a static IP address for the server. The GPRS DTU equipment's data relay program runs in the server, and the program manages the communication channel between the monitoring master station and various substations, and implement the function transmitting data among all the GPRS DTU equipments on the channel. The data is organized by the CDT protocol. The data relay program uses several network programming technologies, including CDT protocol, CRC checksum algorithm and analysis of CDT protocol.At first, this paper introduces several power automation communications technologies, briefly described the characteristics of various communication technologies including GPRS. This paper discusses the feasibility of the GPRS technology used in the substation automation system in the following four sections: the reliability, the performance-to-price ratio, the real-time performance and the constructing convenience of communications system, dnd then proposes three GPRS network schemes.In second, this paper introduces the power monitoring system of Xiang'an Avenue using GPRS technology. GPRS network adopts the solution of Internet static address. This part describes the project in three sections. First, GPRS-Internet network: how to construct the GPRS-Internet network, job description of GPRS DTU equipment and configuration of GPRS DTU. Second, Substation: the configuration of hardware in the substation, the function of substation, and the function of monitoring software. Third, monitoring master station: the function of monitoring software system, the architecture of software system and the details of programming.In order to describe how to develop the GPRS DTU equipment's data relay based on CDT protocol, this paper introduces CDT protocol, CRC checksum algorithm, procedure of protocol analysis, SOCKET programming model, and finally describes the details of the data relay.