The main monitoring unit of the system can program different protocols through the programmable bridge to meet the needs of interface with different intelligent devices. Modbus bridge nw-bm85c002 MB bridge / multiplexer, each bridge has four communication ports to communicate with the intelligent devices in the Bay layer. The bridge converts the Modbus protocol data into protocol, and establishes network communication with PLC through MB 10 network. At the same time, the central signal screen is also equipped with a programmable bridge nw-bm85c485, which is connected with PLC through MB network, Each programmable bridge has four RS-485 ports with programmable communication protocol. In this scheme, two ports are programmed to communicate with the central control center through iec-60870-7-101.
The network communication layer of the system communicates with the control center through RS-422 interface of the programmable bridge and IEC60870-5-101 international standard protocol; The lower network communication layer communicates with the intelligent devices such as the microcomputer integrated protection measurement and control unit in the main substation or the protection panel through the Modbus standard protocol of RS-422 interface of the bridge, so as to meet the technical requirements of the control, measurement and protection of the integrated automation system of the substation. Through the communication between the bridge and the intelligent equipment and the control center, the protocol conversion is realized by the bridge, which reduces the load rate of the CPU module of PLC and improves the reliability of the system.