SCADA Systems Components Defined

By Mark Sen Gupta

Industry Trends

SCADA systems are utilized in a number of different industries. These include transportation (rail, mass transit, and traffic control, as well as asset tracking, and so on), telecommunications, mining, electric power, oil and gas, and water and wastewater. The specifics of SCADA system design dif-fer from industry to industry, as application software and system response are matched to the specific needs of each industry. In some cases, particu-larly in developing countries, a single utility may be responsible for electric power, oil and gas, and water and wastewater operations. In these cases, a single SCADA system might sometimes be called upon to meet the diverse functional requirements of all three industries.

SCADA System Components

SCADA has been an accepted technology for monitoring, controlling, and automating a number of different industrial and commercial applications for many decades. The earliest applications were in oil and gas pipelines, water utilities, and electric power distribution.

SCADA’s original function was to monitor and control processes or opera-tions that had wide geographic distribution. Early systems used communication technologies that are very slow and bandwidth-constrained by today’s standards. These include both phone lines and voice band radio.

Due to these limitations, the SCADA applications were designed to get by using relatively small amounts of data sampled at infrequent intervals.

SCADA System Components

This is in stark contrast to the capabilities of today’s communication technologies, where high data transport speeds and virtually unlimited bandwidth are available. The contrast will only increase as communica-tions technology continues to evolve exponentially. Based on communication advancements alone, today’s SCADA systems represent a quantum improvement over the earlier, communication-constrained sys-tems. Combined with powerful new SCADA applications, today’s SCADA systems are providing important enabling technology for enterprise inte-gration, collaboration, and business process transformation.

The latest SCADA systems encompass a new generation of technology components. These are easier to integrate and provide vastly improved capabilities and functionalities. Today, SCADA systems are being considered for a wide range of applications that extend well beyond the scope of traditional SCADA.

A typical SCADA system consists of at least one master station, multiple RTUs, and a communications network. The centralized master station pro-vides supervisory functions and a human machine interface. The geographically distributed RTUs collect and forward data from local field devices and perform local control functions, as needed (such as turning a pump on or off, or opening or closing a valve). The communications network connects the mas-ter station to the RTUs.

Traditional master stations were closed, proprie-tary, and purpose-built. Today’s master stations are more likely to be commercial UNIX work-stations or Windows-based personal computers (PCs) or servers. To take advantage of economies of scale, several suppliers that serve both the SCADA and distributed control system (DCS) markets, use common workstation platforms for both. Multiple master stations are typically net-worked with one another and other systems within the plant on a high-speed communications network, such as Ethernet.

SCADA system RTUs are microprocessor-based devices designed to moni-tor and collect data as well as perform some control functions. These functions depend upon the requirements of the specific industry and the technology used by the RTU manufacturer. The industry has developed smart RTUs with the capability to execute logic and PID closed loop con-trol. The SCADA market has moved away from the traditional proprietary RTUs and toward multi-purpose devices, such as programmable logic con-trollers (PLCs) and intelligent electronic device (IEDs). However, traditional, purpose-built RTUs are still likely to be used in environmental-ly challenging applications, such as where extremes of moisture, temperature, or humidity are present or low power consumption is re-quired.

ARC identifies the principal components of a SCADA system by the following groups:

  • SCADA hardware and bundled software
  • Application software
  • Project and maintenance services

SCADA Hardware and Bundled Software

The typical SCADA system will be comprised of a number of workstations, RTUs, and IO points depending upon the requirements of each specific application. SCADA hardware specifically includes:

  • All controllers, data concentrators, application processors, IO, MTU, workstations, and communications networks. PCs used for system con-figuration and real-time control are included in SCADA components. PLCs and flow computers, sold in conjunction with SCADA systems and functioning as RTU, are also included as components
  • Bundled system software, including operating systems, compilers, con-figurations, database management software, or diagnostics
  • All remote terminal units (RTUs) and IO used to collect data and pro-vide control to field devices. RTUs may take the form of a traditional, smart, or proprietary RTU; a PLC; an IED; or a hybrid device

Operating System and Application Software

All workstation and supervisory software is included in this category. Workstation platforms may use UNIX, Linux, or Windows-based operating systems. Many SCADA suppliers sell industry-specific application packages with their systems. Application software may include any or all of the elements of bundled systems software described above, but is sold separately from SCADA hardware. Application software can be addressed to a specific area of focus. The focus of SCADA application software continues to grow due to the positive impact that SCADA-based knowledge can have on business performance. Oil and gas SCADA applications are grouped into two major segments, upstream and midstream:

  • Upstream
  • Custody Transfer - Gas/Liquid Measurement
  • Reservoir Management
  • Full Field Management
  • Subsea
  • Midstream
  • Pipeline Integrity Management
  • Custody transfer
  • Scheduling and planning
  • Advanced control
  • Leak Detection
  • Environmental compliance
  • Terminal Automation


The services component for SCADA projects are categorized into two groups: project services and maintenance/support services. Project services include system design, process engineering, and systems engineering.

  • Project Definition Application Software Development
  • System Design Checkout and Startup Services
  • Process Engineering Project Management
  • Systems Engineering Maintenance Services

Maintenance services encompass all post-installation and facilities planning services provided by the supplier’s field services organization for which a manufacturer engages into a contract or purchases per day. In addition to traditional maintenance services, services can include engineering, programming, training, network management, and complete facilities management.

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