Hydra - A DNP3 multiplexing platform for SCADA system switchover

Supervisory Control and Data Acquisition (SCADA) systems are used in many industries, particularly in the control of nationwide electric grids. These systems may by law, technical obsolescence, or failure, need to be replaced by newer ones. However, the testing and handing over of functions from the old SCADA to the new one (i.e., switchover) has to be done with minimum risk and maximum continuity of operations. Several vendors offer partial solutions to this problem, but they usually imply downtime or incomplete testing. We have developed a communications multiplexing system, Hydra, that allows for several Master Terminal Units (MTU) to poll telemetry data from the same set of Remote Terminal Units (RTU) using the DNP3 over TCP/IP protocol without requiring their reconfiguration. This system multiplexes DNP3 traffic so that MTUs share access to the same network of RTUs which allows for complete testing of functionality prior to commissioning with virtually no downtime, therefore addressing the main issues of concern when transitioning between SCADA systems. This paper deals with the motivation, architecture and implementation of Hydra.