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Message-Based Communications for Pipeline SCADA. Stephen Koenig, P.E. Smarter Infrastructure for Oil and Gas December 3, 2013 Houston, TX. source: http://www.epa.gov/gasstar/images/newsroom/fall11-valve.jpg. source: http://www.welkereng.com/wfms/portfolio/images/pipeline.jpg.
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Message-Based Communications for Pipeline SCADA Stephen Koenig, P.E. Smarter Infrastructure for Oil and Gas December 3, 2013 Houston, TX source: http://www.epa.gov/gasstar/images/newsroom/fall11-valve.jpg
source: http://www.welkereng.com/wfms/portfolio/images/pipeline.jpg
Data stored in the Corporate Accounting System Data calculated by meter station Flow Computer Sensor Data Data stored in the meter station Flow Computer source: http://www.transport4.com/PublicSite/t4publicweb/home.aspx
Network Subscribe Publish Data Source Data Destination Message Broker Data Source Data Destination Data Source Data Destination Data Source Data Destination Message Format Topic Payload Messaging - Basic Concepts • Multiple data sources (publishers) send messages to multiple data destinations (subscribers) • Destinations subscribe by “topic” • Payload can be anything: text, binary, fixed fields, etc up to 250Mbytes in size • Broker supports multiple delivery options (QoS)
Automation to SupportPipeline Operations Tank Gauging System Flow Computer Remote Terminal Unit Comm Processor Satellite Link to Control Center P T F
source: http://www.northerngateway.ca/assets/498x245_contentimages/EnvironmenatlResponsibility/Pipelineassesment.jpg
source: API RP 1165 – Recommended Practice for SCADA Displays
Traditional Approach to SCADA Poll/Response • Host & RTU’s are serial devices – typically Programmable Logic Controllers • “Round Robin” polling • Data format optimized for mininimum overhead
Problems with Poll/Response systems • Host “owns” communications link • Dedicated circuits are too expensive • Alarm latency increases with RTU count
Challenges in Use of Message-BasedCommunications for SCADA • Controls – limited life in system • Stale Data – replace poll/response functionality in event-driven system • Security • Flexible architecture may result in new vulnerabilities • Message-based system must be as secure as traditional poll/response • Need for continuous improvement
Benefits of Message-Based Approach to SCADA • Topic/Payload Message Structure • IP Routing • Intelligent Front-End Processor • Many-to-Many Architecture
Benefits - Topic/Payload Message Structure • “Wildcard” subscriptions • Support for multiple applications on one message broker • Use of version number in topic • Facilitate prototype and test of new clients • Allows site-by-site migration strategy
Benefits – IP Routing Scalability
Benefits – IP Routing -- Redundancy Reducing the Impact of Failure Broker1 Broker2 Broker3 Broker4 • Provisions for broker equipment failure • Provisions for loss of primary communications link – backup link
Benefits – Intelligent Front-End Processor Broker1 Broker2 Broker3 Broker4 • Adapt Serial Devices to IP/VSAT • Move polling/response to field • Ability to handle multiple RTU protocols • Local intelligence can supplement or enhance control system
Benefits – Many-to-Many Architecture • Significantly reduced project schedules • Off-line systems receive live data for testing
Future Opportunities for Message-Based SCADA Systems(from a 2005 perspective) • “Flight Simulator” for pipeline Controllers • Interface to business systems • Real-time meter ticket transactions to shippers and other carriers’ business systems • Distributed SCADA