IDC Technologies. Practical SCADA Systems for Industry. Perth. Australia
As its name suggests, SCADA has been around for as long as process control and data acquisition existed. Its first appearance can be traced somewhere back in the 40's. The need of those systems back then was dictated by the necessity to control remotely located stations. It was too expensive to send a crew of technicians every time when some variable needed changing. The first very primitive "SCADA" systems comprised analogue sensors connected to panels of meters, lights and strip chart recorders. The control exerted back to the process was in those days extremely limited. It was done manually by operators, who observed the data, displayed on the panels and then operated various knobs, levers and buttons in order to keep the desirable set point within acceptable limits. Needless to say, this type of supervisory control and data acquisition was extremely ineffective.
Soon after that, the utilisation of the existing telephone lines become a viable option for process control and data acquisition of remotely located stations. Initially those systems operated on stepping switch systems and on tone modulation. In parallel to this the first process control relay systems were developed, which were the crude predecessors of the PLC systems. Those technical inventions albeit highly cumbersome were around until the 60's. Then with the invention of the solid state devices (such as the bipolar junction transistors) the SCADA systems went through a real revolution. Instead of using one telephone line for each analogue signal, the data from multiple points could be digitised, collated and sent as a batch digital signal over just one single pair of telephone line. Initially the signal was modulated as pulses or as variable frequencies, but this soon also became obsolete.
By the mid-60's computer based master stations became common and they were able to control effectively basic process variables in real time. The term RTU (Remote Terminal Units) was also coined in the 60's following the development of the semiconductor technology, which made those units much more independent and self-reliant as possible. During the 60's, 70's and the 80's the source code of the language on which two devices "talked" to each other (also known as ‘communication protocol') was not released to the public by the different vendors. They were doing this with the intention to keep as larger part of the SCADA market for themselves as possible. This gave rise to dozens, of how we call them today ‘proprietary' protocols. The trouble with them was that once a specific SCADA system was installed from a particular vendor, the clients became disproportionally dependent for any future installations or modifications on the same supplier.
All this started to change in the 90's with the invention of the Internet and its mass proliferation around the globe. The open protocol TCP/IP, which was used for common communication between any two devices on the World Wide Web became more and more common amongst the newly built SCADA systems. This gave the users the advantage to ‘mix and match' SCADA components from different manufacturers. The proper technical term for this is ‘interoperability', which means the ability to combine together in one system equipment from competitive vendors. The greater interoperability allows the end user to build highly versatile and cost-effective monitoring and control systems.
In parallel to all this, the first ‘smart instruments' were introduced, which again totally changed the landscape of the existing SCADA systems. These highly intelligent devices are capable of performing many additional functions. Those devices are not content with simply transmitting data about the monitored process variables and executing control operations. In addition to this, they are also capable of communicating digitally a great deal of massive auxiliary information, which could be extremely important and very useful. For example, almost all of them can perform self-check, self-calibration and self-monitoring. Often, they can be reprogrammed and serviced from a distance with a negligible impact on the process. Because they operate on a TCP/IP, they are assigned with their own IP address and this is why they appear as normal nodes on the LAN (Local Area Network), connected to the SCADA system. An operator with sufficient privileges can monitor those devices from any point of the globe, running a SCADA package installed on his laptop, tablet or even mobile phone. Of course, all these newly added capabilities of modern SCADA systems has risen security concerns to an entirely new, extremely high level.
Here you can find two SCADA reports, produced by my ex-student. He graduated in June 2013 and he is now employed He has spent a lot of his personal time to put up those reports. They contain a lot of useful information about the SCADA systems. I dare to say that the students enrolled in the SCADA course will be half prepared for it if they learn the content of the two reports, given below. This is the reason why I have uploaded them here, with his permission, of course. If you study SCADA with me you will be required to produce similar reports on various aspects of SCADA systems.
Attachment:- ELE_Question.zip