PLC Programming

SCADA System (Supervisory Control and Data Acquisition): What is SCADA?

SCADA stands for “Supervisory Control and Data Acquisition”.

That’s a mouthful, which is why engineers often refer to it as a “SCADA System”, or just “SCADA”.

This tutorial will cover an introduction to SCADA systems and architecture, SCADA applications, and SCADA programming. i.e. all the basics you need to know about SCADA systems.

I’ll guide you through the nuts and bolts of SCADA systems and how they make a difference in both tech and business realms.

The business side of things is often overlooked, which means companies are missing out on opportunities (and hence money).

Let’s dive right in then.

Content:

What is a SCADA system?
How does a SCADA system work?
SCADA architecture
SCADA Software
SCADA Technology
SCADA Applications: Where do we use SCADA Systems?
SCADA System Examples

What is a SCADA System?

SCADA stands for Supervisory Control and Data Acquisition and is a system for monitoring and controlling and as the name implies, data acquisition. It is widely used in factories to monitor and control production lines and machines. A good way to make an understanding, of what a SCADA system is and where it can be used, is to see it in relation to the automation pyramid.

SCADA systems are located at the monitoring and supervising level in the automation pyramid. The automation pyramid is a concept published in ISA-95 and IEC 62264-3, in an attempt to describe how different systems work together. At the top you have all the information systems for handling business, planning and logistics. And at the bottom you have all the operational systems. SCADA systems are placed right in the middle of the automation pyramid. Right where IT (information technology) meets OT (operational technology).

SCADA System in the Automation Pyramid from ISA-95 (IEC 62264-3)

Below the SCADA system is all the operational technology like PLC’s, sensors etc. The job of SCADA is really to control and monitor all this OT. But at the same time also to send and receive information from the MES or ERP system above. Information that has to do with business and planning. Like an order for example.

How does a SCADA System work?

Again, the SCADA system is the meeting and connection point between information and operation. The SCADA basics is really about exchange of information and the ability to control and monitor. Especially the latter is how you will often see SCADA systems in use.

What a SCADA system physically will look like is a screen. More than often multiple screens where an operator can both control and monitor all relevant components in a unit, machine or even a whole plant. This could be visualized with e.g. a P&ID (piping and instrumentation diagram). Most important is it, that the operator understands the different parts of the SCADA system and what they control/monitor.

SCADA system with PI&D for controlling and monitoring

All these screens are essentially HMI’s or human-machine interfaces. They are the interface between the operator and the machine. Back in the days an HMI was really just a bunch of push buttons and control lamps. But now you will often have a touch screen either at the machine or in a control room.

But if all these screen are called HMI, what is SCADA exactly then?

SCADA Architecture

Put simply HMI is part of SCADA. Because where the HMI is just the screen or the interface itself, SCADA is an application or a whole system behind all those screens. A SCADA system can have many HMI’s to control and monitor different parts of a plant.

If we take a closer look at the architecture of SCADA it becomes clear, that it contains much more than just HMI’s. It is a whole infrastructure of devices that can communicate. The SCADA application typically runs on a server. Clients like desktop computers and screens can then function as HMI’s by connecting them to the server. Since the operational devices like PLC’s and RTU’s are also connected to the server, we can now use the SCADA clients to control and monitor operations.

An RTU or remote terminal unit is a bit like a PLC. You can connect sensors to the RTU and it will convert their signals to digital data. This digital data will then be available for the SCADA system.

Let’s take a quick trip through time to see how SCADA systems evolved from their humble beginnings to the complex structures we see today.

1st Generation: Monolithic
2nd Generation: Distributed
3rd Generation: Networked
4th Generation: Internet of things

Knowing the history of SCADA systems really gives you an insight into the development of it. How SCADA has developed from a simple monolithic architecture to cloud based infrastructure. But even though the fourth generation of SCADA systems has arrived, many of the existing systems still belong to the third or even the second generation. That’s why, for us that works with SCADA systems, it’s essential to be familiar with the older systems.

Monolithic Architecture

The first SCADA systems had only one supervisory station. It was back then when PC’s and networks didn’t exist. Instead of PC’s mainframe stations were used. The function of these early systems were limited to monitoring sensors. You will only find these systems in museums now a days.

First generation SCADA architecture with an IBM mainframe computer

Distributed Architecture

With the invention of Local Area Networks (LAN) came the distributed systems. Networking now meant that you could have multiple control and supervisory stations. You could now have a SCADA system where a network between the supervisory stations made communication possible.

Although rare, second generation SCADA systems still exists today.

Networked Architecture

As the networks technology and protocols evolved and we started to see Wide Area Networks (WAN), new possibilities for networking and communicating also became possible for SCADA systems. This meant that SCADA systems could now not only be used in a single plant, but throughout several plants with physical locations far from each other. With networked architecture, the data and supervisory can be accessed anywhere, even from a physical location different than the plants.

Networked Architecture of a SCADA system, where control of multiple plants is centralized

Most SCADA systems out there are in fact still build with networked architecture. Although more and more are aiming towards IoT, there is still a long way to go.

Internet of Things (IoT)

The 4th generation of SCADA systems are the ones we’re building now. It is part of the big Industry 4.0 revolution. Here, both Internet of Things (IoT) and decentralized data communication are important. These new technologies gives us a whole lot more freedom and flexibility in the architecture.

Industry 4.0 where all components are interconnected and can communicate with the SCADA system at all times.

In fact, the whole SCADA architecture is designed to centralize the control and monitoring (data acquisition). The whole idea is to have one system or one application. But with IoT, this idea is changing towards a more decentralized architecture, where every component can communicate to every other.

Although this new architecture is the future of automation there are still many security issues. The data from the SCADA systems are most often highly valuable and sensitive for business and putting those in the cloud requires a strong layer of security.

SCADA Software

Let’s take a look at some real world SCADA applications to see what they really can do. There are a few big players on the market. But many of them have scalable solutions in order to meet requirements on different levels. Some SCADA applications though work best on big sites with multiple servers and clients, while some work best in smaller sites and applications.

You will have many factors to consider when choosing the SCADA software that fits your needs. Both regarding business and technical aspects. Just think about it like this:

Which variables do we need to monitor and control in order to help the process and the business? It is very important to have a specification of this before you’re considering which SCADA software you’re going to use.

Lifespan of the SCADA software

Another thing many people tend to forget about is the lifespan of the SCADA software. A SCADA system can be a heavy investment and you will often expect a lifespan of the system to be somewhere between 5 and 15 years.

As we all know technology is developing faster than any other industry. In fact technology doesn’t only evolve fast, it evolves exponentially faster. Just take Moore’s Law as an example. The processor of computers double the amount of transistors each year making them exponentially faster.

Technology races ahead, leaving older methods in the dust. What was cutting-edge five years ago might now be seen as slow or outdated.

Request for Information (RFI)

RFI or Request for Information is usually a business term used to describe the capabilities of vendors and suppliers. Take note of this term, because it it highly relevant in relation to choosing SCADA software.

If the lifespan of your SCADA system is expected to be 10 years for example. You want to be sure that you can as a minimum get support, updates, ability to expand and so on for that period.

Historian Software

When you’re working with SCADA software you will often meet the term Historian or Historian Software. In terms of a SCADA software solution the Historian Software is the software responsible for logging the data collected from the field data interfaces.

It is called a historian because the software saves the data (often in a database) with timestamps so that the data can be used for trends, analytics and logging.

Using historian software is crucial for many SCADA applications and industries. Some industries like the food or the pharma industry even has legal requirements (FDA 21 CFR Part 11) for logging data. The standard for batch control ISA-88 is a good example of how logging can be implemented.

All the logged data from the historian can also be used to analyze. The data is in fact worth a lot for a company, since analyzing it often can lead to e.g. better maintenance plans and optimized production.

SCADA Technology

A SCADA system consists of many different technologies for everything from logging and saving data to communication protocols and standards for accessing data.

Both as a SCADA programmer and when you’re choosing a SCADA solution it is important to know about these technologies. One thing you should especially notice here is that new isn’t always better.

When you’re choosing a new computer new and updated technology is almost always better. But this is not true in the world of SCADA systems. A SCADA system is often an extensive system with many components that has to work together. At the same time the system has to be secure.

For these two reasons the best solution is not always the solution with the latest technology, but rather the solution with the most stable and secure technology. Not all components, especially on the lower level (PLC’s and RTU’s) are capable of utilizing the latest technology for communication etc.

Database

The place where all the collected data is stored is usually a database. It is also from the database you can later access those data for reports and analytics. You might have heard about an SQL database before, and SQL is also the main database technology used by SCADA systems.

SQL stands for Structured Query Language and is a programming language used to manage data in databases. You can use it to insert, remove, edit and import or export data to the database. In fact, the SCADA system is using SQL commands to manage the database.

You can find other query languages but SQL is by far the most used today, not only by SCADA software but also to manage databases in general. SQL databases can be hosted on your own servers or as a cloud solution.

OPC and OPC UA

Compatibility with the PLC and RTU platform you’re using is of course very important. You need some way for the SCADA system to access the data from these field devices. One of the primary technologies for this is OPC.

OPC stands for OLE for process control and is a standard for accessing data in field devices like a PLC or RTU. SCADA systems usually use OPC server and client technology to communicate with the PLC. To be more precise, the part of OPC used is called OPC DA (data access).

The PLC is set up to be an OPC server which will then translate the data to fit the OPC protocol. In your SCADA system on the other hand you will have an OPC client that can access those data via the OPC protocol.

What is smart about the OPC protocol is that most modern PLC’s support it. This means that you don’t have to buy a SCADA system from the same vendor as the PLC’s you’re using.

Alarm Management

Almost all SCADA systems include alarms. Handling these alarms is referred to as alarm management and is everything from setting and resetting alarms to managing the priority of alarms.

Alarms can be system defined alarms or user defined alarms. Where system defined alarms has to do with the status of the hardware or system itself, user defined alarms are defined and programmed by the user.

User defined alarms include discrete and analog alarms. Discrete alarms are triggered by the digital status of a bit. Whereas analog alarms are triggered by analog values that exceed defined limits.

In many SCADA systems resetting of alarms is restricted. A triggered alarm often means that something went wrong and action needs to be taken. Often by a qualified person which means that only he should be allowed to reset the alarm.

Data Visualization

When most people think about SCADA systems they think about one or several screens where the process or part of it is visualized. It is that visualization that gives the operator the possibility of controlling and viewing data from the system.

Data visualization can be any sort of visualization of a given stream of data. Trends and charts are often used to visualize the development of a value whereas tables and color is often used to indicate the state of a discrete variable. Colors has been used quite a lot in SCADA systems to visualize, but with new standards like ISA-101 and ISA-112 the term “grey is good” and high performance HMI was introduced.

One of the emerging technologies used for visualizations and screen development is HTML5. I would say this has tree major reasons:

Fast Development
Easy to Access
Many Developers

With HTML5 you can rapidly create prototypes for your screens and visualizations. This makes the development process much faster. At the same time HTML5 is also very accessible especially if done in responsive designs. HTML5 can be read with any browser and both computers and devices like smart phones and tablets.

Data Analytics and Machine Learning

Apart from just visualizing the data an increasingly bigger part of the job of a SCADA system is to analyze those data. Data analytics and machine learning are not just buzz words. They are a part of the Industry 4.0 revolution and with it your SCADA system becomes smarter.

You can argue that analytics of the data has been done throughout the history of the SCADA system. Most SCADA systems provide a reporting system where reports with production, process and system data is presented. These data were often analyzed by humans in order to optimize production or maintenance.

Enter machine learning and its smart algorithms. These new kids on the block can sift through data, learn from patterns, and uncover optimization strategies that might slip past human analysis.

SCADA Applications: Where do we use SCADA Systems?

SCADA has a wide range of applications ranging from small units to big plans and even enterprises with several plants. Monitoring can be useful in every aspect of automation because it allows us to collect useful data. Not only can this data help us decrease production cost, they can also help us improve the efficiency of a production and reduce maintenance cost. All because SCADA gives us the data to analyze.

Improve equipment performance
Higher quality product
Reduce maintenance cost

Many industries are using some sort of SCADA application to monitor and control their processes. But each industry has different requirements for what is needed to be monitored and controlled.

Here are just some examples of industries that uses SCADA systems for monitoring and controlling:

Manufacturing
Power Plants
Water Treatment Plants (waste water)
Pharma Industry
Food and Beverages
Oil and Gas Industry
Recycling

Each industry and each individual company also has different requirements for the SCADA system they are using. Some companies are big and have several plants, while others are just one plant or even just one processing unit.

A SCADA system for the oil and gas industry can be completely different from a SCADA system for a power system or power plant.

SCADA System Examples

Below here you can check out some of the biggest SCADA system providers on the market. They are compatible with most PLC and control systems and uses the latest and most used communication standards.

Choosing a SCADA system from a widely used provider is often the best solution, since they often have much better support, many more developers available and are often the most stable.

FactoryTalk View SE, Rockwell

One of the most used PLC platforms is from Rockwell Automation. And their SCADA software FactoryTalk View is no exception to that.

A big advantage here is that it is relatively cheap and therefore used by many people. For students on a budget it is a great way to enter the world of SCADA software and learn how to build and program a SCADA system.

The popularity among students also makes FactoryTalk View attractive for companies to use, since there will be more developers who have experience with this software.

InTouch, Wonderware

From Wonderware, now owned by Schneider Electric, comes InTouch which has become one of the biggest SCADA vendors on the market. Although InTouch is fairly new to the market it is now already considered one of the best.

The Wonderware system platform is a modular and very flexible SCADA system with many “plug-and-play” components. Because of the modularity of this system means that if you’re choosing this SCADA software you can fairly easily customize it to your needs.

Antoher advantage of InTouch is that they use open communication standards and can work with most PLC platforms.

Citect SCADA, Schneider Electric

Schneider Electric also has their own SCADA software. Or had should I say. Because after they bought Wonderware, that became their primary SCADA solution and they basically stopped developing further on the Citect SCADA. Or almost at least.

With this said Citect SCADA is still one of the widely used SCADA systems out there and as a SCADA developer you definitely has to know about this platform. In fact it has now become a part of the Wonderware SCADA solutions.

The thing here is that Schneider Electric needs to continue the developement of Citect SCADA because it is such widely used. Citect has many years on its back and is therefore an extensive SCADA system with many features developed over time by requests of their users.

https://www.youtube.com/watch?v=GsxcHJffuhM

Experion SCADA, Honeywell

Another one of the widely used PLC platforms (especially in the US) is Honeywell. On the SCADA system market they are also a key vendor since they provide a software platform for SCADA and HMI programming.

You can use their software both for a stand-alone SCADA system or you can use it with Honeywell’s PLC platform (e.g. C200 and C300 platform) and RTU’s like the ControlEgde RTU.

Even though the SCADA software from Honeywell works best and is optimized for the Honeywell PLC’s and RTU’s, you can also use it with other PLC platforms. They provide many standard SCADA interface drivers for e.g. OPC.

iFIX, General Electric

One of the biggest industrial companies in the world General Electric (GE) is also a major player on the SCADA market. One of their software solutions is called iFIX and it is a very flexible SCADA system.

There are several reasons that this system is so flexible. But one of them is the possibility of rapid development of screens with HTML5. Another reason is the many drivers which allows you to set up networked and distributed systems and which allows connection and data exchange with most modern PLC’s.

Ignition, Inductive Automation

Ignition is a SCADA system that truly takes advantage of the new IoT architecture. If you want a system that is up to date with all the Industry 4.0 standards and technologies Ignition from Induction Automation is a very good choice.

Ignition is fairly new to the SCADA market compared to many others. But it is still a very solid SCADA software using the latest technologies. Because of that and the fact that it works very well with most PLC platforms has made many companies choose Ignition as their SCADA solution.

SIMATIC WinCC V7, Siemens

The Siemens SCADA system is known as WinCC and has been around for many years. Siemens is in fact one of the biggest players on both the PLC and SCADA market and many companies are using the Siemens platform.

Although most of the Siemens products are a bit pricey I would argue that you get good value for the money. Siemens is again a big company and they have been developing on their PLC and SCADA platforms for many years. Their products are therefore very stable and that is a critical factor for many companies.

WinCC is widely used which also means that there is a lot of training material out there. Both offered by Siemens themselves, training academies, and PLC training courses online. You can even find great tutorials on YouTube.

MC Works64, Mitsubishi Electric

If we look towards to Asian SCADA market, which by the way is massive, we will find Mitsubishi as one of the biggest vendors. Their SCADA software is called MC Works64 and is a group of products that beside MC Works64 includes products for monitoring energy use, historian, equipment control etc.