A study on link redundancy control in standard communication protocols for remote monitoring and control systems

摘要

In this paper, we propose methods of standby redundancy control of communication lines in ISO/IEC 60370-5-101, which is a standard communication protocol for remote monitoring and control (telecontrol) and has come into wide use in applications of electric power distribution and generation, water treatment, and so on. The protocol doesn't have consideration about such redundancy control, and it is difficult to introduce additional communication sequences into the protocol to detect communication faults. In this paper, we propose an algorithm to detect communication faults and find out the points of the faults from erroneous behavior of message sequences for monitoring and control without altering data formats and message sequences of the protocol. Furthermore, it is strongly required that the standby redundancy control will be realized with modifying existing implementations of the protocol as little as possible. For this, we propose a concept of "a redundant communication line" and its implementation, which makes most improvement in the protocol for redundancy implemented in its physical layer, minimizes alteration in its link layer and upper layers, and makes the protocol stack easy to be implemented and portable onto various platforms. Finally, we show how an actual communication system detects faults and recovers from them with the proposed algorithm.