Routing SCADA data through an enterprise WAN

Houston Lighting and Power (HLandP) and many other large utilities have invested substantial resources in developing integrated enterprise wide area networks (WANs). The WAN provides unprecedented opportunities for integrating information throughout the corporation, resulting in improved efficiency and reduced costs of operation. In contrast, present dedicated point-to-point SCADA data circuits from the energy management system (EMS) to remote terminal units (RTUs) are not currently integrated with the network, nor replicated in any offsite backup system. An integrated approach might integrate communications from selected RTUs over the WAN to a backup system or the EMS. Such an approach would potentially provide improved disaster recovery, more efficient use of communications, reduced maintenance costs, and improved availability of operational data. RTU data, however, is fundamentally different from most other WAN traffic in that it is critical to the moment-to-moment operation of the utility and consists of a large number of messages repeated frequently and continuously. There are valid concerns as to whether the stability, availability, and inherent latency of the WAN would be adequate to support operations of a backup or primary SCADA system. There are also concerns about the adverse effects that SCADA traffic might have on the WAN. These concerns led to the project featured in this article, which tested the operational suitability and effectiveness of routing SCADA data between selected RTUs and a central site on the WAN