Introduction to PLC and SCADA

Introduction to PLC's

Programmable Logic Controllers

Bedford Associates, founded by Richard Morley, introduced the first Programmable Logic Controller in 1968. This PLC was known as the Modular Digital Controller MODICON that the company derived its name. The history of PLC, said Howard Hendricks by Dick Morley provides an interesting insight into the early development of PLC.

Schnieder Quantum PLC

Programmable Logic Controllers were developed to provide a replacement for the relay of large control panels. These systems were inflexible require significant wiring or replacement provided that the control sequence would be changed.

The development micro processor from mid-1970 have enabled the Programmable Logic Controllers have to assume more complex and larger features such as speed higher processor.

Ladder Logic

PLC had to be easily maintained by the technicians and staff electricity. In support of this programming language Ladder has been developed. Ladder Logic is based on the relay contact symbols and technical were used for through wiring diagrams of electrical control panels.

Until recently there has been no formal programming standard PLC. The introduction of IEC 61131 standard in 1998, provides a more formal approach for coding. PLC manufacturers have so far been slow in adopting of the standard partial implementation. The articleIEC SearchEng 61131-3, a standard for PLC Software RW Lewis offers an introduction to the standard.

Documentation Programs for early PLC is nonexistent or very poor, only to offer simple and basic comments addressing, making large programs difficult to follow. This has improved much to the development of PLC programming packages.

SCADA and HMI

The first programmable logic controller interface operator in much the same way that the relay control panel, via buttons and switches for the control and indicator lights.

The introduction of the personal computer (PC) in the 1980s allowed the development of a computer-based operator interface, those which initially through simple Supervisory Control and Data Acquisition (SCADA) and more recently, dedicated through the operator control panel, known as human-machine interfaces (HMI).

The History of the PLC
As Howard Hendricks told by Dick Morley

The following are some myths related to the ten early years of the company programmable controller. These fables may or may not have a basis of truth, but overall, they are the best that my memory is fraught with Alzheimer can do at this time. As has often been in other articles and reports, implementation and Modicon programmable controller industry as a whole is well documented. The programmable controller was detailed in the New Year's Day 1968, and from then until now, a slow and steady growth has enabled the manufacturing and control process to use the applications-oriented software.

The first few days however, were not so simple or simple. We had some real problems in the early days of convincing people that a box of software, although cast iron cased, could do the same thing something like 50 feet of cabinets, relays and associated wiring. The process was really difficult, and deserves some of the stories that I hope the reader delights in front, as it moves through the winding marsh of my mind.

One of my first recommendations was that the programmable controller, according to my own system architecture specification, not need to go fast because I felt as if speed was not a criterion, because it would go as fast as was necessary to do so. The initial team, which was never delivered, only had 125 words of memory, and speed was not a criterion as mentioned above. You can imagine what happened! First, immediately ran memory, and second, the machine was too slow to carry out any function anywhere near the response time of the relay. Response times Liaison exists in the order of 1/60th of a second, and the topology formed by many cabinets full of relays become code is significantly more than 125 words. We have extended the memory of 1K and 4K there. At 4K, it stood the test of time for a while. Initially, marketing and memory sizes sold in 1K, 2K, 3K, (?) And 4K. the 3K was obviously limited the 4K version management for field expansion could be done easily 4K.

The question of speed, in part, was part of the initial designs. No interruptions were necessary because the conditions of external signal directly in writing to the memory requirements without any control or "conventional type operating system. This allowed the processor to pay attention to the solution of logic instead of cleaning I / O. As a result, of course, the processor had to be much more processing power normally associated with this team size, and secondly, the system had to be made to run faster.

We've increased the memory size, as mentioned above, but to get to run fast, we had to break the machine in three different components. Initially, the programmable controller was designed for a processor board and a memory and the manipulation algorithms and logical to do in software. This approach has been painfully slow, both in the store generic "buy computers and other items.

We did, however, manage to significantly speed machine by making a third major. This was called the solver logic. On board algorithms Solver solves the dominant logic associated with the solution of the ladder logic without involving software and classical approach general purpose processing. This means we have finished with three boards, memory, logic solver and processor. This step allowed us to obtain the velocity you need on this specific computer application to solve the simple problem of perception of several cabinets full of wiring the relay.

We had also taken a modular approach to the programmable controller. During the ceremony, the name means Modicon Modular digital controller. The modularity, however, was soon abandoned because, as everyone knows, open architectures are not good. Instead, the premise was that the marketing of a large footprint in it are contained sets of problems they want solved. This means that a purchaser of programmable controllers could buy a large number of these units, and software and hardware would be identical in a wide range of applications in its plant. Service, maintenance and total cost of living would be substantially lower than the lower cost of perception an open architecture and modular expansion. Though initially a supporter of open architecture modular expansion, soon convinced by the market, but it was crazy.

We took one of the first units that was intended for the machine tool industry, because of my background Bedford Associates from consulting to one of the applicants at the beginning of this equipment. This particular applicant has been early and Chuck Bryant Grinder in Springfield, Vermont. We took the machine there, and was heavy. This was the 084. The 084 was in the trunk of my old Pontiac, and because she needed help carrying in, asked some people to help with Bryant. We went and opened the hood, and the first observation by a viewer outside the programmable controller, said, "Thank God it, s not another piece of pastel of the sheet.

We hypothesize this comment in particular that the robustness of visual design was to his liking, and humans (as opposed Mars), suggests that this same attitude was deep in the construction of the machine in hardware and software. In fact, this was the case, and the machine as a result, was built sturdy, had no ON / OFF switch, had no followers, make no noise and not carry out the system.

To recall for a moment — in the selection of the nuclei of the earliest memories, which in itself was a revolutionary step, we selected these nuclei and applied Shannon s law. Shannon, s Law assumes that the signal to noise ratio is what makes good or bad signals. There are several ways to get the power of the signal-to-noise ratio, one is in great As the code, be triply redundant, and much use and a lot of error checking. There is another way that is perfectly compatible with the theory, which is used a lot of signal strength in another domain. A nice change, a car battery and a D-Rated bulb works pretty well for a long time period.

So what we did was go instead of error checking, triple redundant and stuff we have, and search and find high energy, great heart ferrite memories that had a lot of energy per bit. We follow the same course today. The energy per bit is very important — like Shannon s theory is in his most famous role in 1948, that the noise signal to noise power is what gives the transmission. the way in which signal strength was to increase energy bit. This is what I felt was more important than getting the energy per bit increased through double transmission. But I digress. Bryant Grinder Chuck and place, and you liked it so much the team that never bought one. In turn, I thought it was a good idea, as many did at that time, tried to develop their own.

One of our first major customers, however, Landis Landis, PA. The team flew by private jet, and with apprehension, because we arrived late (as always), brought the team to Landis. In doing so, she tripped over the threshold. The KA-RASH team was on the floor! Not worth much, we chose the above equipment, rolling in hooked up, and low and behold, it worked pretty well.

Now, Landis was pleased and surprised. They were happy because it worked, but was more pleasantly surprised — not because the team worked — but because the guys from Modicon expected the team despite a big fall. In other words, people were not Modicon, t nervous at the fact that he fell on the floor on the threshold.

Landis later took and coils of wire wrapped around the welding machine to induce electro-magnetic noise to see if they could make it fail. We have been there! Was used to test the programmable controllers with a Tesla coil reached a quarter inch to half inch of arc in any part of the system, and the programmable controller still had to keep running. There were significant strangeness in relation to the programmable controller. For example, I had no ON / OFF switch. He had no means to load software. He had fans. It worked well. Could survive evil, physical and thermal environment. It was not standard in the computer industry. There were many things that are more difficult in the acceptance of the programmable controller and early acceptance was more difficult indeed.

Our sales in the first four years were abysmal. Early innovators like Landers and General Motors, of course, the heroes of our eyes, but they would buy a small number of units and testing them in the field before committing themselves more evening. We had a customer in the business of public services it took approximately six to seven years before making a decision, but the first.

We have never sold any programmable controllers on the market in question, which was control of machine tools such as lathes, grinders and other things, but we did, As luck would have faced in the market transfer line was and remains the main long-term market for the application of programmable controllers. Discreet manufacturing parts in a machine environment, ie mass production, remains, and will probably be for the future, the mainstay of the programmable controller industry.

Some of the more interesting stories center around the personality and experience as opposed programmable controller. Modicon, s in the third president (or fourth if you count my two week stay) was Don Kramer. When Mr. Kramer was elected President, we decided to go out and celebrate in Lanum Club in Andover. A time, we feel that we should celebrate more than two martinis and food. When we left the tent for the Club Lanum, Don put aside the comment that "the place is dirty and needs a paint job. When we left, I mentioned to Don that as president he has to change what you say, not very open — has to be a little careful what you say because employees, customers, and the boards tend to take what he tells the truth. Instead of listening to the meaning, to hear statements literals, and beware. Lanum We went to the Club and had a bright pleasant two-hour debate, food and beverages. In return, upon entering the lobby Modicon, we realized we had about scaffolding and painting people. Lou and we wondered why these people are painting, because, at that time, we do not, I have no money. Who ordered this painting? And Don Kramer Lou looked into her eyes and said, "Why did Mr. Kramer. Nuff said.

As mentioned many times, its author, who, s — me — Dick Morley is supposed to be the inventor of the programmable controller. This is at best partially true. What made the company Modicon and the programmable controller was not really off the 084, but 184. The 184 is made in the design cycle by Michael Greenberg, one of the best engineers I've known. He, Rousseau and Lee, president and Marketeer, came with a specification and a design that revolutionized the business of automation. who built the 184 on the objections from this server. I was a purist and believes that all the bells and whistles and things weren t "pure, and somehow it was polluting my 'glorious design, Dead wrong again, Morley! were specifically Right on! the 184th was a walloping success, not 084 — No, the invention of the programmable controller — but a product designed to meet the needs of the market and the customer called 184 and took off and Modicon programmable controller of the company and the industry it is today. Congratulations the two chefs Rousseau — Lee and Mike Greenberg.

The issue of quality of programmable controllers is a story that is often taken for granted. The gentle reader must remember that our engineering people in the computer industry, where reliability in those days was a ghost ghost — a design, a ghost of the costs. People felt that the reliability is something that the others did, and that if we could offer faster computers, but they didn, t work, everything would be well.

When the programmable controller was designed, was designed to be reliable. We use many energy per bit of information through use of D-Rated recorded components, memory large nuclei, relatively stable and large printed circuit boards, totally enclosed and piping systems cooling. No fans were used, and outside air was not allowed into the system for fear of contamination and corrosion. Mentally, we had programmable controller imagined that under a truck, outdoors, and being driven around Texas — driven around, led around Alaska. In these circumstances, anted us to survive. The other requirement was that I was on a pole to help run a utility or a microwave station that was not climate controlled, and that is not suited to everyone. In these circumstances, it would work for the years he was destined to be? Can be wall? Could be screwed into a system that is expected to last 20?

The comic side of this is despite the fact that not all designs and very carefully tried to make this system as inherently reliable We could not pay, but also in construction. In other words, was designed to be built, was designed to be designed, and was designed to be reliable. We, however, as engineers, do not, do not understand counters and manufacturing. both have their grail, shipping later this month. From what we check at the time, shipments were made independent of quality, independent of whether or not the system running.

In the early days of the driver Modicon programmable, although I was not, ta direct employees and an owner, I give my phone number from his home to many of our customers so that critical if they had a problem, you could call me directly. Several calls indicates that when sent near the end of the month, say, October 34, the team would not be presented, and secondly, when you opened the box and took the machine apart, the cards were missing, the pins on the bottom of the cabinets, and some card not fully inserted. In other words, that the end of the month was much more important to deliver equipment running. put it mildly, we pissed! How do we as engineers to maintain quality without constant monitoring is more difficult to design and entrepreneurship. What we did was define and design "blue boxes. cabinetries These were that the system had to operate and run continuously for a minimum of 24 hours under load and under conditions that vary. The box was constructed of plywood, but his first intention was to heat cycle in a number of programmable controller I / O loads. Also ran as a specification, a Tesla coil was to be used in the programmable controller, and that the vibration and shock with a hammer (rubber) would be part of specification.

This may seem unscientific to many of you, but suppose you try to get your computer running while someone deliberately tries to destroy with a rubber hammer or spark coil you can put anywhere on the system. Remember that your intention is to stop the processor. This combination monthly shipments significantly depressed during the first period. As a result, however, the message got through. Not only are we building furnaces and testing, and pay attention to heat and spark and RF emissions, the system would run continuously, even in the shipping box to get the maximum number of hours before the commission we could. It was important for us that we are the errors and not the client and your client school.

The language itself, Lister stairs have some discussion. This particular language was not the invention of Modicon. Our hypothesis is that the language is very old, and originated in Germany to describe relay circuits. If you look Lister ladder, it has been our technical community for so long, somehow we think these actually look like little symboligies relays. In fact, the level, so sa mnemonic rule-based language, very modern and very high, but is designed in a Darwinian way over a period of several decades.

Ladder logic of construction, "if … then … is a very powerful today is used in expert systems and other rule-based languages. The symbolism, allowing normally open and normally closed situations as well as parallel and serial representation was used for many decades before the invention of the programmable controller. I've worked on machines where the number of size C and D size prints were hung on special racks, and would be up to three feet thick on the value of documentation drawing sets.

The staircase name comes from the fact that on the right side of the drawing is a line of tension and the left lane is another power, and in the middle of a horizontal way, is the statement or the switching sequence of logical elements we call relays or relay logic. The initial 084 were only logic functionality, and as a result was marginal. In other words, everything he did was to replace the relays instead of improving the functionality of a factor of ten, which is the business rule. Immediately, of course, on the basis of the response from customers and our own frustrations, we put something in the language of stairs magazines such as add, multiply, subtract, and other features that go far beyond the capacity of relay and entered the field of mathematics and set theory. This was not yet sufficient, however, and we needed a way to make a "call to subroutine 'use of symbolism and representation Lister ladder.

A software engineer, Chuck Schelberg, and I were in the conference room a day trying to figure out how we can make a generic call to the functionality that far exceeded the relay symbols and representation, and approached with the function of "DX. This function is a block that would be an element of the performance ladder logic that can perform many functions including arrays, functions of the drive motor, servo functions, extended math functions, PID loops, ad nauseam. We thought it would be a representation occasionally and use these features, and there was much to be done for separate programmable controller to modify the software. Wrong again!

The first customer took delivery of a programmable controller using the DX function, had a capacity to be predictable and operate in real time. The RUN light went out, and the time to run a full scan or conversion of ladder logic was well beyond the time allowed. Each line has a DX function he. Once again we have learned that when you improve the functionality, use it all. I've never designed a team that had too much memory. I see only the computers that are designed very little memory. The same applies to any other functionality. Conventional wisdom seems to think that the price / performance depends on one thing — — Price when, in fact, my experience has been that the customer does not care about price.

This price / performance is more diatribe, one of the lessons we have learned is that the client wants functionality over the entire life cycle cost of installing the posts. The customer also wants to ease installation, to have fun and to be proud of the work you do. After he, s finished, you never want to return .. The team should work as installed and as a basis. At one point, programmable controller meantime before failure in the field was 50,000 hours. This is far above almost any other electronic or computer control.

The concept of languages and high level languages is important. The programmable controller, as it evolved, began to demand more and more power, more and more memory. The memories rose continuously, and power. It is estimated that at one time, the mid-1970s, programmable controller that had the equivalent of two processors MIPS and 128 kilobytes of memory, which at that time was a mini-computer significantly the power rating. Why? High-level languages require energy to run. If we take the equivalent of the scale of Lister statement "If … Then … the high level language, represented here requires a substantial amount of compiler interpretation, if you will, the underlying code generation. In other words, this statement generates important underlying code to be executed quickly, security, and contain within them, all aspects of resource allocation and resource operations. The highest level is the language, the more powerful the processor apparently must be in order to implement the language. Lister ladder is a high level of regulation based on language which, until now, haven, t been much talk in these terms. Our clients deal programmable controller as a relay box, and well they should. The theory of language is neither necessary not desirable for most customers known. Customers, however, understand your problem, and indeed are much smarter than the design engineers, because the dimensions of the problem far exceeds the problem relatively easy to design a software system and language. Lister ladder requires high performance that is one reason why it has trouble running on the computer staff, even today

INTRODUCTION TO SCADA

SCADA stands for Supervisory Control and Data Acquisition. Usually refers to an industrial control system: a computer control system and control of a process. The process can be industrial, infrastructure base or installation as described below:

Industrial processes are the manufacturing, production, power generation, manufacturing and refining, and can operate in continuous, batch, repetitive, or discrete modes.

Infrastructure processes may be public or private and include treatment and water distribution and wastewater, oil and gas pipelines, electricity transmission and distribution and communication systems of large size.

Fund processes occur both in public and private buildings, airports, ships and stations space. That monitoring and HVAC control, access and power consumption.

A SCADA System usually consists of the following subsystems:

A Human-Machine Interface or HMI is the apparatus which presents process data to a human operator, and through which the human operator monitors and controls the process.

A control (computer) system, collecting (acquiring) data on the process and sending commands (control) for the process

Units Remote Terminal (RTU) that connects to sensors in the process, converting sensor signals into digital data and sending digital data to the control system.

Communication infrastructure that connects the control system remote terminal units

There, in several industries, a considerable confusion about the differences between SCADA and distributed control systems (DCS). Generally speaking, a SCADA system usually refers to a system that coordinates, but not control, real-time process. The debate in real time control is somewhat clouded by new telecommunications technology, enabling reliable, low latency, high-speed communications over wide areas. Most differences between SCADA and DCS distributed control system are culturally determined and usually can be ignored. As communication infrastructures with more capacity available, the difference between SCADA and DCS will fade.

Systems concepts

The term SCADA usually refers to centralized systems which monitor and control entire sites, or complex distributed systems in large areas (anything between an industrial plant and a country). Most control actions are performed automatically by remote terminal units (RTU) or programmable logic controllers (PLC). The control functions are often limited to host-level intervention, primary or basic monitoring. For example, A PLC can control the flow of cooling water through part of an industrial process, but the SCADA system may allow operators to change set points for flow, and enable alarm conditions, such as loss of flow and high temperature, to be displayed and recorded. The feedback control loop passes through of the RTU or PLC, while the SCADA system monitors the overall performance of the cycle.

Data acquisition begins at the RTU or PLC level and includes meter readings and status reports of the teams that are communicated to SCADA as required. The data is compiled and format so that a room operator control through the HMI can make decisions to adjust or replace control normal RTU (PLC) control. The data can also be fed to a historian, often based a commodity Database Management System to allow the audit trends and analytics.

SCADA systems typically implement a distributed database, commonly known as a tag database, which contains data elements called tags or points. A point represents a single input or output value of control or controlled by the system. Points can be "hard" or "soft". A hard point represents a real input or output of the system, while a weak point of the results of logic and math operations applied to other points. (Most implementations conceptually remove the distinction by making every property a "soft" point of expression, which may in the simplest case, equal to a single hard point.) Items are usually stored as pairs of timestamp value: a value, and the date The time when it was recorded or calculated. A series of pairs of time stamp value gives the history of this point. It is also common to store additional metadata with tags, as the path to a field device or PLC record, comments design time, and alarm information.

Human Machine Interface

A Human-Machine Interface or HMI is the apparatus which presents process data to a human operator, and through which the human operator controls the process.

An HMI is usually linked to databases of the SCADA system and software programs, to provide trends, diagnostic information and management information, such as Routine maintenance procedures, logistic information, detailed schedules for a particular sensor or machine, and expert troubleshooting guides system.

The HMI system usually presents the information to the graphical operating personnel in the form of a mimic diagram. This means of the operator can view a schematic representation of the plant being controlled. For example, an image of a pump connected to a pipe that the operator can demonstrate that the pump is running and the amount of fluid being pumped through the pipeline at the moment. The operator can change the pump. The HMI software will show the liquid velocity in the decline of the pipeline in real time. Diagrams can consist of line graphics and schematic symbols to represent process elements, or may consist of digital photographs of the process equipment covered with animated symbols.

The HMI package for the system SCADA typically includes a drawing program for operators or maintenance personnel use the system to change the way these points are represented in the interface. These representations can be as simple as an on-screen traffic light, which represents the state of a real light in the field, or as complex as a multi-projector display that represents the position of all elevators in a skyscraper or all of the trains on a railroad.

An important part of most SCADA implementations are alarms. An alarm is a digital status point that has either the normal or alarm. Alarms can be created so that when they meet their requirements, are activated. An example of an alarm is the "fuel tank empty" light in a car. The SCADA operator's attention is drawn to the system requiring the attention of the alarm. E-mails and text messages are often sent along with the alarm warning along with directors of SCADA operator.

Hardware Solutions

SCADA solutions often have Distributed Control System (DCS) components. The use of "smart" RTUs or PLCs, which are capable of independently implementing simple logic processes without involving the main equipment is increasing. A functional programming language classes, IEC 61131-3, is frequently used to create programs that run on these RTUs and PLCs. Unlike a procedural language such as C programming language or FORTRAN, IEC 61131-3 has minimal training requirements, under the similar historical physical control arrays. This allows SCADA system engineers to perform both design and execution of a program to be executed on a RTU or PLC. From about 1998, virtually all major PLC manufacturers have offered integrated HMI / SCADA systems, many of them using open and non-proprietary communication protocols. Numerous specialized third-party HMI / SCADA, offering built-in compatibility with most major PLCs, have also entered the market, enabling engineers mechanical, electrical engineers and technicians to configure HMI themselves without the need for A custom program written by a software developer.

Remote Terminal Unit (RTU)

The RTU connects to physical equipment. Typically, an RTU converts the electrical signals equipment to the digital values such as open / closed status of a switch or valve, or measures such as pressure, flow, voltage or current. By converting digital set points of electrical signals and send these electrical signals to equipment the RTU can control equipment, such as opening or closing of a switch or valve, or setting the speed of a pump.

Quality SCADA RTU have these characteristics:

Network data capacity

Reliability of data

Data Security.

Monitoring Station

The term "monitoring station" refers to the servers and software responsible for communicating with the field team (RTU, PLC, etc.) and then the HMI software running on workstations in the control room or elsewhere. In smaller SCADA systems, the master station may consist of a single PC. In larger SCADA systems, the main station may include multiple servers, distributed application software and disaster recovery sites. To enhance the integrity system of multiple servers are often configured in a dual-redundant hot-standby or continuing education that allows control and monitoring in the event of server failure.

Initially, platforms more "open" as Linux were not as widely used due to highly dynamic development environment and SCADA because a customer was able to afford the field hardware and devices to be controlled could usually also purchase UNIX or OpenVMS licenses. Today all major operating systems are used for both servers and workstations HMI station chief.

Operational philosophy

In some installations, the costs that would result from the lack of monitoring system is extremely high. Possibly even lives could be lost. Hardware for some SCADA systems is robust to withstand temperature, vibration, and extremes of stress, but most critical facilities reliability is enhanced by having redundant equipment and communication channels to the point of having multiple control centers fully equipped. A party can not be quickly identified and its functionality automatically taken over by backup hardware. A party can often be replaced without interrupting the process. The reliability of these systems can be calculated statistically and is stated as the average time to failure, which is a variant of mean time between failures. The average time calculated for the failure of these systems high reliability can be of the order of centuries.

Communication infrastructure and methods

SCADA systems have been traditionally used combinations of radio and direct serial or modem connections to meet communication needs, although Ethernet and IP over SONET / SDH is also often used on large sites such as railways and power plants. The remote management or control of the function of a SCADA system often referred to as telemetry.

This has also been threatened with some clients who wish to SCADA data to travel over its pre-established networks corporate network or to share with other applications. The legacy of the first protocols for low bandwidth remains, though. SCADA protocols are designed to be very compact and many are designed to send information to the master station only when the master station polls the RTU. Typical legacy protocols include Modbus SCADA RTU, RP-570, Profibus and Conitel. These communication protocols are all SCADA-vendor specific, but are widely adopted and used. Standard protocols are IEC 60870-5-101 or 104, IEC 61850 and DNP3. These communication protocols standardized and recognized by all major SCADA vendors. Many of these protocols are now included extensions to operate over TCP / IP. It is good security engineering practice to avoid connecting SCADA systems to the Internet so that the surface of attack is reduced.

RTUs and other automatic control devices were being developed before the advent of the industry standards for interoperability level. The result is that developers and management created a multitude of control protocols. Among the biggest providers, there was also the incentive to create their own protocol to "secure" their customer base. A list of automation protocols is being compiled here.

Recently, OLE for Process Control (OPC) has become a widely accepted solution to communicate with different hardware and software, enabling communication between devices, even initially not intended to be part of an industrial network.

Trends in SCADA

There is a trend for PLC and HMI / SCADA to be more "mix and match". In the mid 1990s, the typical DAQ I E / S supplied equipment manufacturer that communicate using protocols property on a suitable distance such as RS-485. End users who have invested in a hardware solution of a specific manufacturer were often restricted to a limited choice of equipment when the needs changed (eg, system expansion or performance improvement). To mitigate these problems, protocols open communication, such as IEC870-5-101/104 and DNP 3.0 (serial and IP) became increasingly popular among OEMs and solution providers SCADA alike. The open architecture SCADA systems allowed users to mix and match products from different manufacturers to develop solutions that were better than they can accomplish is limited to offering a single product provider.

Towards the end of 1990, the shift towards open communications continued with E / S individual manufacturers, so open message structures adopted as Modbus RTU and Modbus ASCII (originally developed by Modicon) through RS-485. In 2000, most the I / O makers offered completely open interfacing such as Modbus TCP over Ethernet and IP.

SCADA systems are coming online with standard networking technologies. Ethernet and TCP / IP based protocols are replacing proprietary standards older. Although certain features of the structure based on the technology of network communication (determinism, synchronization, protocol selection, the suitability of the environment) have limited the adoption of Ethernet in a few specialized applications, the vast majority of markets have accepted Ethernet networks for HMI / SCADA.

"Next generation protocols, such as OPC-UA, SuiteLink Wonderware, GE Fanuc Proficy and FactoryTalk, Rockwell Automation, take advantage of XML, web services and other technologies modern web, making them more easily bearable.

With the emergence of software as a service on the broader software industry, some suppliers have begun offering specific applications hosted on SCADA systems remote platforms via the Internet, for example, PumpView by MultiTrode. This eliminates the need to install and commission systems in end-user installation and takes advantage of security features already available in Internet technology, VPN and SSL. Some concerns include security, reliability of Internet connection, and latency.

SCADA systems are increasingly ubiquitous. Thin Clients, Web portals, and web-based products are gaining popularity with the major providers. The convenience of end users see their processes remotely introduces security considerations.

Security Issues

The shift from proprietary technologies to more standardized solutions and open, with the increased number of connections between the SCADA and office networks and the Internet has become more vulnerable to attack. Consequently, the security of SCADA-based systems has been questioned because they are increasingly seen as extremely vulnerable to cyberwarfare / cyberterrorism attacks.

In particular, security researchers are concerned about:

the lack of concern for security and authentication in the design, deployment and operation of SCADA networks

the mistaken belief that SCADA systems have the benefit of security through the darkness through the use of specialized protocols and proprietary interfaces

the mistaken belief that SCADA networks are secure because they are allegedly physically protected

the mistaken belief that SCADA networks are secure because they are supposedly disconnected from the Internet

Given the mission critical nature of a large number of SCADA systems, such attacks could in the worst case, causes huge financial losses through of data loss or physical destruction, misuse or theft, even loss of life, either directly or indirectly. If these concerns will cause the abandonment the use of SCADA systems for mission critical applications on architectures and security settings more remains to be seen, given that at least some influential people in business and government circles believe that the benefits and lower initial costs of SCADA based systems still outweigh costs and risks potential] Recently, multiple security vendors such as Byres Security, Inc., Industrial Defender Inc., Check Point and nameless, and N-Dimension Solutions have begun to address these risks by developing lines of specialized industrial firewall and VPN solutions for TCP / IP based SCADA networks. The problem, said Eric Byres, CEO of Byres Security, is that "as organizations of the infrastructure of many are doing a good job, others are lagging behind. When you have this diversity of effort, you are only as effective as its weakest link.

In addition, the ISA Security Compliance Institute (ISCI) is emerging to formalize SCADA security testing starting as early as 2009. SICI is conceptually similar to private testing and certification that has been performed by vendors since 2007 as the certification program's Achilles Wurldtech Security Technologies, Inc. and the certification of the Mu Security MUSIC, Inc. Over time, the standards are defined by ISA SP99 WG4 replace these initial efforts of industry consortia, but probably not before 2011.

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