DCS Communication Interface for SCS and SCADA

DCS and SCADA are connected through SCS.

The DCS connects with SCS and SCS is connected to SCADA.

DCS and SCS are connected by MODBUS TCP/IP duplicated communication using optical fiber cables.

SCS is Master and DCS is slave. Therefore, SCS carries out the control and selection of duplicated communication lines.

MODBUS communication interface between the master and the slave is the duplicated communication links. One of these links will be Link A and the other will be Link B.

The master can check a communication condition (Master’s Communication Module Failure, Error Respone from the slave and No Respone from the slave), on both lines periodically, detect wheter each line is normal or not.

In case of a read function (code 02, 04), the master will transmit a command message and receive a respone message through which ever link that is healthy with the slave. In case an unhealthy link is detected, the changeover to healthy link will be executed by control logic in the master. Link A has priority. So, the data via Link A will be used when both lines are normal.

Abbreviations :

• DCS = Distributed Control System
• SCS = Substation Control System
• SCADA = Supervisory Control and Data Acquisition