What is a SCADA system?

SCADA is an acronym for Supervisory Control And Data Acquisition, which is a computer system for gathering and analyzing real-time data. Such systems were first used in the 1960s.

Table of Contents

  1. What is SCADA?
  2. Where is SCADA used? What industries?
  3. The value of SCADA.
  4. Capabilities of SCADA.
  5. How SCADA systems work.
  6. Example: simplest SCADA system.
  7. RTUs and PLCs to HMI
  8. Migrate to LAN from serial.
  9. Data presentation.
  10. How to Evaluate SCADA.
  11. SCADA RTU functions.
  12. SCADA Master (HMI) functions.
  13. Quality matters more than price.
  14. Surveying your SCADA sites.

The SCADA industry was essentially born out of a need for a user-friendly front-end to a control system containing PLCs (programmable logic controllers). SCADA networks allow remote monitoring and control of an amazing variety of industrial devices, such as water and gas pumps, track switches, and traffic signals.

One of the key processes of these systems is the ability to monitor an entire system in real time. This is facilitated by data acquisitions. These include meter reading and checking statuses of sensors. These data points are communicated at standard intervals depending on the system. Besides the data being used by the RTU, it is also displayed to a human. The human is able to interface with the system to override settings or make changes when needed.

SCADA monitoring equipment can also be seen as a system with many data elements called points. Each point is a monitor or sensor and these points can be either hard or soft. A hard data point can be an actual monitor; a soft point can be viewed upon as an application or software calculation. Data elements from hard and soft points are usually always stored and logged to create a time stamp or history.

In essence, a SCADA application has two elements. They are:

  1. The process/system/machinery you want to monitor and control. This can take the form of a power plant, a water system, a network, or a system of traffic lights.
  2. A network of intelligent devices that interfaces with the first system through sensors and control outputs. This network, which is the SCADA system, gives you the capability to measure and control specific elements of the first system.

Where is it used?

SCADA can be used to manage many kinds of gear. Typically, these systems are used to automate complex industrial processes where human control is impractical. Around the world, modern SCADA systems are used in many industries. These include:

Manufacturing: SCADA systems manage parts inventories for JIT manufacturing. They also regulate industrial automation and robots. To ensure good output, they monitor process and quality control.

Buildings, facilities and environments: Facility managers use SCADA to control devices. These include HVAC, refrigeration units, lighting and entry systems.

Electric power generation, transmission, and distribution: Electric utilities use SCADA systems to detect two key things. Those things are current flow and line voltage. They monitor the operation of circuit breakers. They also take sections of the power grid online or offline.

Water and sewage: State and municipal water utilities use SCADA to monitor and regulate water flow. They also track reservoir levels and pipe pressure.

Mass transit: Transit authorities use SCADA to regulate electricity to subways, trams and trolley buses. They also automate traffic signals for rail systems. They can track and locate trains and buses with SCADA. They can also control railroad-crossing gates.

Traffic signals: SCADA regulates traffic lights, controls traffic flow and detects out-of-order signals.

What is it?

There are three main elements to a SCADA system:

Each RTU collects information at a site, while communications bring that information from the various plant or regional RTU sites to a central location. They also occasionally return instructions to the RTU.

Communication within a plant is conducted by data cable, wire or fiber-optic. Regional systems most commonly utilize radio. The HMI is fundamentally a PC system running powerful graphic and alarm software programs.

The HMI displays this information in an easy to understand graphics form. It archives the data received. It transmits alarms. It also permits operator control as required.

How Does it work?

A SCADA network consists of one of more Master Terminal Units (MTUs). These are utilized by staff to monitor and control a large number of Remote Terminal Units (RTUs). The MTU is often a computing platform, like a PC, which runs SCADA software. The RTUs are most likely small dedicated devices that are hardened for outdoor use and industrial environments.

As we saw earlier, there are several parts of a working SCADA system. These systems usually includes signal hardware (input and output), controllers, networks, user interface (HMI), communications gear and software. All together, the term SCADA refers to the entire central system. The central system usually monitors data from various sensors that are either in close proximity or off site (sometimes miles away).

Functions performed by a SCADA system.

A SCADA system performs four functions:
  1. Data acquisition.
  2. Networked data communication.
  3. Data presentation.
  4. Control.

These functions are performed by several kinds of SCADA components:

What to Look for in a MTU.

Your SCADA master should display information in the most useful way. This allows your human staff to oversee operations. Your master should also intelligently regulate your managed systems.

Here's a checklist.
SCADA master essentials:

Flexible and programmable response to sensor inputs.
Look for a system that provides easy tools for programming soft alarms. (reports of complex events that track combinations of sensor inputs and date/time statements) and soft controls (programmed control responses to sensor inputs).

24/7, automatic pager and email notification.
Why pay personnel to watch a board 24 hours a day? If equipment needs human attention, the SCADA master can automatically page or email directly to repair technicians.

Detailed information display.
You want a system that displays reports in plain English. You need a complete description of what activity is happening and how you can manage it.

Nuisance alarm filtering.
Nuisance alarms desensitize your staff to alarm reports. Your people can start to believe that all alarms are nonessential alarms. Eventually they may stop responding even to critical alarms. Look for a SCADA master that includes tools to filter out nuisance alarms.

Expansion capability.
A SCADA system is a long-term investment that will last for as long as 10 to 15 years. So you need to make sure it will support your future growth for up to 15 years.

Redundant, geo-diverse backup.
The best SCADA systems support multiple backup masters in separate locations. If the primary SCADA master fails, a second master on the network automatically takes over. There is no interruption of monitoring and control functions.

Support for a lot of protocols and equipment types.
Early SCADA systems were built on closed, proprietary protocols. Single-vendor solutions aren't a great idea as vendors sometimes drop support for their products or even just go out of business. Support for a lot of open protocols safeguards your SCADA system against unplanned obsolescence.

Potential benefits of SCADA.

Reliability and robustness.
These systems are used for mission critical industrial processes where reliability and performance are paramount. In addition, specific development is performed within a well-established framework that enhances reliability and robustness.

Maximize productivity.
Maximizes productivity and ensures continuous production. SCADA's design is centered on multi-level redundancy to ensure constant communication and operation of your system.

Improve product quality.
Analyzes and controls the quality of manufactured products using standard SCADA functionality. This includes Statistical Process Control (SPC). Advanced statistical alarms allow your personnel to perform predictive calibration of process parameters. This prevents out-of-limit deviations before they occur.

Reduce your operating and maintenance costs.
Through the deployment of a centralized SCADA system you can significantly reduce operating and maintenance costs; fewer personnel are required to monitor field gear in remote locations. This results in increased operator effectiveness. Also, less maintenance trips are required. This results in decreased maintenance and training costs.

Integrate with your business systems.
A SCADA system can be easily integrated with your existing business systems, leading to increased production and profitability. In addition, this system implementation allows you to transform, analyze, and present real-time information. This info travels throughout the enterprise for prioritized decision-making.

Preserve your capital investment.
When you spend money to improve operations, you need to ensure prolonged use. SCADA's open system design protects against control system obsolescence. It can be easily scaled to meet growing demands on your operations.

How Can I Install a SCADA system?

There are five phases in creating a functional SCADA system:

  1. The DESIGN of the system architecture includes the communication system. Also involved in this initial phase will be any site instrumentation that is not currently in existence. It will be required to monitor desired parameters.
  2. The SUPPLY of RTU, communication, and HMI gear. This consists of a PC system and the required powerful graphic and alarm software programs.
  3. The PROGRAMMING of the communication gear. and the powerful HMI graphic and alarm software programs.
  4. The INSTALLATION of the communication equipment and the PC system. The previous task is typically much more involved.
  5. The COMMISSIONING of the system, where communication and HMI programming problems are solved. The system is proven to the client. Operator training and system documentation are also provided.

A complex SCADA system can be complex to configure. However, it is most likely much easier to operate.

How DPS Telecom Can Help You.

As demonstrated in this "What is SCADA?" guide, building the right SCADA system for your business isn't simple. It's easy to spend more than you need, but there are also opportunities to save money and improve operational efficiency that you don't want to miss. It's hard to learn everything you need to know and still perform your daily job. DPS Telecom can help you plan your SCADA implementation, with expert consultation, training and information resources. DPS telemetry gear is built with the capabilities you need and we are committed to helping you get the best SCADA system for your specific needs.

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