SCADA Systems: Controlling the Industrial World
By John C. Colwell, Bishop & Associates Inc.

Supervisory, Control and Data Acquisition (SCADA) systems represent a subset of industrial control systems. And, like industrial controls, SCADA systems have become network-centric, leveraging the power of intelligent sensors and actuators, networking, computing, and communication assets to achieve optimal control and situational awareness, typically in a large, complex system. System operating parameters are aggregated, processed, and displayed at what is referred to as the human machine interface (HMI). The HMI can consist of a computer monitor or a custom display panel, which reports status information across the system being controlled. Illustrated above is a model of a petrochemical plant application by Honeywell.

SCADA systems are widely employed in the following industries: 

• Electric power generation, transmission, and distribution systems

• Water management and sewage treatment facilities

• Mass transit systems

• Buildings and facilities management

• Traffic control systems

• Oilfield monitoring and control systems

• Refineries and chemical processing facilities

• Factory automation systems

Early SCADA systems employed 20 milliamp current loop signaling protocols and communicated directly through programmable logic controllers (PLCs). The PLCs communicated via a direct connection, or a modem connection, to a control center. Each sensor and actuator required its own dedicated home run connection to the controller. This protocol was largely replaced by RS-485, which allowed multi-drop digital communications along a single home-run bus connection to the PLC. Later, fieldbus technology became widely used in SCADA systems. See the ConnectorSupplier article, Industrial Networks.

While this is mature technology, we believe that SCADA systems are poised for accelerated growth. Three significant areas of application come to mind: 

• National Security: Ports worldwide handle an estimated 100 million containers annually. In most instances, the containers are shipped inland by truck. Presently, only a fraction of these are subject to rigorous inspection. By the end of this decade, we expect to see deployment of automated inspection and tracking stations both at the seaports and along major transportation corridors. Inspection may include scintillation counters and sniffers to detect radioactive and explosive materials. RFID technology will be employed for asset tracking and route validation.

• Traffic Management: In North America, it is estimated that more than two billion man-hours are wasted annually as the result of traffic delays over and above normal communing times. Moreover, the fuel wasted during these delays is estimated at three billion gallons per year. As a result, the U.S. federal government is working with the states to improve the efficiency of mass transit systems and to develop better methods of dynamically managing vehicular traffic. This problem is not limited to North America. 

• Global Infrastructure Development: Outside of North America, there is growing demand for hydroelectric and nuclear power generation, port facilities, oil and natural gas terminal facilities, mass transit, highways, and other large scale infrastructure projects, which make extensive use of SCADA systems. 

Demand for SCADA systems is on the rise; developments of the last decade in the area of wireless access technology and standardization have made SCADA systems easier and less costly to implement. Wireless communication has long been a component part of SCADA, mostly in the form of proprietary systems. The IEEE 802 wireless standards, on the other hand, have resulted in low-cost silicon implementations, and a robust mix of competitive products.

In order to assess the value of connector shipments attributable to SCADA systems, it is necessary to look at several industry sectors: industrial, telecom, and computer.

World SCADA Market for Connectors - 2008
$US - Millions

The world value of connector factory shipments for equipment employed in SCADA systems is estimated at $356 million in 2008. The five-year compound average annual growth forecast is 16 percent. Industrial sensors and actuators represent the largest segment, valued at $177.4 million in 2008. Computer and peripheral equipment accounts for $112.5 million. Telecom includes primarily enterprise networking equipment and is valued at $65.7 million. By 2013, the value of connector shipments is expected to reach $750 million.

Typical telecom equipment includes wireless routers. Illustrated below, at left is the Motorola MOTOMESH Quattro wireless access point/router, as deployed in a municipal safety and traffic control system. At the center is a Cisco wireless router. On the right is a mobile Internet switching controller from Sun Microsystems. The switching center provides routing, switching, and management functions. It also supplies the connection to the wired world.

The advantage of the mesh topology is that the mesh is capable of providing its own back-haul link. If a portion of the network is destroyed, an alternate link is established. Connectivity options between access points and the control center include wireline, (coaxial, shielded twisted-pair, and fiber optic cable) and wireless (proprietary, UHF/VHF, microwave, GSM/GPRS, satellite, and WiMAX).

Illustrated above left, is a solar-powered, remote telemetry, ultrasonic sensor for non-contact fluid level detection. The HMI/control center for a wastewater treatment facility, serving Houston, Texas, is pictured right.