Design and analysis of communication network for distributed SCADA system [for electric railways]

This paper presents the design of hierarchical communication network for a Supervisory Control and Data Acquisition (SCADA) system. Some key points, such as data transmission synchronizing, database distribution, data transformation, and the network communication optimization at the supervisory level of communication network are discussed. At control level, based on the specificity of communication lines for electrified railways, the authors utilize the structure of two-layer ring telecommunication network, as well as the efficient bi-directional polling scheme in software design. Then, an analysis for the scheme under normal and disturbance conditions is given. By means of the scheme, software switching-over at fault point of channel is realized automatically.