Substation Automation System Based On Ethernet Technology Research

First, a layered and distributed network model based on Ethernet is presented to solve following problems: there is no an uniform communication protocol applied in substation and the speed of data transmission is too slow. In the newly presented model, the application layer uses modbus protocol, the transmission layer uses TCP and the Media Access Control protocol uses IEEE802.3 standard. The monitoring computer collects measuring data by polling method. Modbus and Ethernet protocol have been the de facto standards in industry, and accepted by most companies, so the application of Mobus/TCP will make devices from different vendors to work properly together in the same network. Secondly, The future substation will transfer not only measuring data, but also information such as gragh, sound and video to the dispatching center. However, the traditional RTU mode can only transfer some simple information, it will not meet the requirements of the future substation. A web-based remote supervisory control system for substation is presented to solve this problem. The Browser/Server mode is applied in this system, various graph and data can be seen through Internet Explorer. The method has following advantages: simple in programming, maintenance-free for clients, etc. In addition, to improve the reliability of traditional automatic apparatuses, PLC is used to implement some functions such as automatic re-switch and automatic put-in of standby power source. The simulation test shows that PLC has advantages such as flexibility in programming ,safety and high reliability, it can replace traditional automatic apparatuses. At last, An expert system used to automatically generate switching sequences is also presented. Knowledge production and frame representation are used to build rule database, status database, topology database and property database, these databases can describe all information of a substation. Forward reasoning based on rules is used as reasoning strategy to generate switching sequences through comparing the differences between the initial status and the final status. The application of the system will solve folio whig problems: much time are consumed and easy to make mistakes when the operator writes switching sequences.