The only display element in our model SCADA system is the light that comes on when the switch is activated. This obviously won't do on a large scale - you can't track a lightboard of a thousand separate lights, and you don't want to pay someone simply to watch a lightboard, either. You need your SCADA system to report intelligent and usable data to the appropriate person in a timely manner. While a light may tell you that something is wrong, it will not tell you what is wrong and why it happened. When you are dealing with remote sites that may take a technician hours to get to, this type of information can mean th difference between network uptime and hours of network downtime. You cannot not afford to have a small light on your board be the only data you have about your site.
A real SCADA system reports to human operators over a specialized computer that is variously called a master station, an HMI (Human-Machine Interface) or an HCI (Human-Computer Interface). The master station receives data from the devices that report to it. It then translates that data into a human-readable and meaningful format. This is why the system is sometimes also referred to as the afore mentioned HMI or HCI.
The SCADA master station has several different functions. When an RTU or other device has a malfunction, the device sends a signal to the master. The master continuously monitors all sensors and alerts the operator when there is an "alarm" - that is, when a control factor is operating outside what is defined as its normal operation. The master presents a comprehensive view of the entire managed system, and presents more detail in response to user requests. The master also performs data processing on information gathered from sensors - it maintains report logs and summarizes historical trends.
An advanced SCADA master can add a great deal of intelligence and automation to your systems management, making your job much easier. Features such as a user-friendly graphical interface, maps, data trend logging, protocol mediation, and a web browser interface are features that advanced SCADA masters might have. When searching for the right SCADA master, look for one that has tools that allow you to gather meaningful data and receive detailed alarm notifications from your equipment. Features such as these will help you prevent damage to your equipment and limit network downtime, saving you valuable money and time.
Unfortunately, our miniature SCADA system monitoring the widget fabricator doesn't include any control elements. Controls allow you to set variables and remotely control automated operations such as opening a door, turning a valve, running a generator when the power goes out. They are essential features for remote sites and save you valuable windshield time by limiting how often you must send a tech to your site. So let's add one. Let's say the human operator also has a button on his control panel. When he presses the button, it activates a switch on the widget fabricator that brings more widget parts into the fabricator.
Now let's add the full computerized control of a SCADA master unit that controls the entire factory. You now have a control system that responds to inputs elsewhere in the system. If the machines that make widget parts break down, you can slow down or stop the widget fabricator. If your factory loses commercial power, you can have a back-up generator started. If the part fabricators are running efficiently, you can speed up the widget fabricator.
If you have a sufficiently sophisticated master unit, these controls can run completely automatically, without the need for human intervention. Of course, you can still manually override the automatic controls from the master station.
In real life, SCADA systems automatically regulate all kinds of industrial processes. For example, if too much pressure is building up in a gas pipeline, the SCADA system can automatically open a release valve. Electricity production can be adjusted to meet demands on the power grid. Even these real-world examples are simplified; a full-scale SCADA system can adjust the managed system in response to multiple inputs. SCADA is used in a variety of industries as well. Manufacturing, Electric power generation, mass transit, traffic signals, water and sewage and distribution are just some of the industries that utilize SCADA to make processes go smoother and to increase productivity and profitability.