VII Международная студенческая научная конференция Студенческий научный форум - 2015

SCADA – is a special supervisory control system responsible for the informative data acquisition about the current enterprise production and its control.

The main advantage of SCADA-system is the ability to monitor and control of many remote objects (from 1 to 10000 control points, sometimes at the distance of thousands kilometers from each other) or one territory spread object.

The typical examples are:

• Oil conduits;

• Gas-lines

• Water pipelines;

• Remote power stations

• Water supply points

• Diesel engine power plants

The purposes of SCADA- systems are:

• Data exchange with Communication device (the device communicating with the controlled object). This device can be an industrial controller as well as input/output board.

• Information according the set algorithms.

• The information representation on the display of the monitor in the form recognizable by a human.

• The formation of data base in accordance with the process information.

• Alarm and emergency message control.

• Preparation and generation of reports about industrial processing.

• Archiving and the consequent viewing of the process information.

• Connection provision with the external applications (DBCO Data Base Control System), tables, text processors and so on. In the industrial control systems such applications are applications MES.

The main SCADA task is the information collection about many remote objects, which come from the control points and the imaging of this information in the entire dispatcher center. Besides, SCADA should provide the long-term archiving of the received data. At the same time a dispatcher often has a possibility not only to passively observe the object but also to control it within certain limits depending on different situations.

SCADA- systems implementation provides the enterprise the following advantages

• The integral system of data exchange on line via special drivers;

• All the incoming information is processing in real time

• The convenient human-machine interface

• The data base containing all the technological operations of the enterprise

• The non-stop making and generation of the enterprise technological processes reports

• The connection between the inner automation control system and the external supplements including the Data Base Control System, text problems, tables and so on.

The general structure of SCADA

All modern SCADA-systems include three main structure components:

• Remote Terminal Unit (RTU) is a remote terminal, which is connected directly to the controlling object and provides control of the task in real time. The scope of RTU forms is wide: the primitive gages which take the information from object and specialized multiprocessor digital complexes, processing the information in tough real time conditions.

• Master Terminal Unit (MTU), Master Station (MS) – dispatcher control unit (main terminal) retrieving data processing and high level control. Depending on a system MTU can be presented in some different forms: beginning from one computer with the additional link-up devices up to big main frames or working stations and servers united into the local net. As a rule during MTU building there used different methods of improvement of the system reliably and safety. MTU is often called SCADA-server.

• Communication System (CS) is the communication system (connection channels) between RTU and MTU. It is necessary for the data transmission from the remote points (RTU) to the central dispatcher interface and for the control signals transmission back from MTU to RTU. As the communication system the following data transmission channels can be used:

1. Isolated lines – sole or leased, copper cable or optical wires;

2. Private radio nets;

3. Analog telephone lines;

4. Digital ISDN;

5. GSM (GPRS).

In order to duplicate the connection lines the devices can be connected to several nets, for example, to the isolated line or stand-by radio channel.

At the moment most of SCADA-systems are based on MS Windows platforms.

Taking into account the continuous strengthening of Microsoft positions at the operational systems market, it should be noticed that even the developers of multiplatform SCADA-systems such as United States DATA Co consider that the further development of their SCADA-systems on Windows NT platform is in priority.

The software system is considered to be open if the data formats and the processing interface are defined for it. This provides an opportunity to connect the outside independently developed components.

There is often a challenge for the automation systems developing companies to create their own (not considered within the SCADA systems) software modules and to integrate them into the automation system. That is why the openness of the system is a very important characteristic of SCADA-systems. In fact the system openness means the system specifications calls availability (in SCADA terms), realizing this or that system service. It can be the access to the graphic function or to the function of operations with data bases and so on.

The modern SCADA-systems give a wide range of drivers or i/o servers and have well developed means of creation their own software modules or drivers of bottom level new devices. Drivers themselves are developed by means of standard programming languages.

In order to connect input/output drivers to SCADA there used two mechanisms: the standard dynamic data exchange (Dynamic Data Exchange DDE) and OPC exchange by means of OPC-servers, for instance.

In SCADA-systems the main mechanism, used for the connection with the external world is OPC protocol (OLE for Process Control), though sometimes there are used DDE mechanism.

DDE due to its capacity and reliability restrictions is not used for the information exchange in real time scope.

Instead of DDE Microsoft Company offered a more capable and reliable data transmission instrument OLE (Object Linking and Embedding). On the base of OLE there appeared a new standard OPC (OLE for Process Control OLE) which is made for the industrial automation market.

OPC standard, at first, enables to unite at the object level the different control systems functioning in the heterogenic media. At second it removes the necessity to use different non-standard equipment and the communication software communication drivers.

OPC interface allows different options of exchange: the receipt of «raw» data from physical devices, from the wide – spread control system or any of the appendixes.

Conclusion

The functional abilities of the most widely distributed commercial systems are basically comparable. The programming technology is close to the intuitional comprehension of the automation process. Besides, the capable objective orientated programming which is used in the most of these packages make these products easy to familiarize for the wide scope of users.

All the systems are open. They provide an ability to add the self – developed functions, which have the open protocol for developing the собственных drivers, the развитую net support, a possibility to include ActiveX-objects and доступность to the standard data base.

The important peculiarity of all the most wide-spread commercial SCADA-systems is the great number of supported different programming logical controllers.

InTouch, Factory Link, GENESIS, RealFlex systems support dozens and hundreds of drivers which confirms their leading position within this parameter.

The building of the прикладной system based on any of the familiar commercial SCADA-systems sharply сокращает the needed knowledge in the sphere of classical programming. This allows concentrating on the efforts to assimilate the knowledge in the applied sphere itself.

Nowadays SCADA-system developers working on Windows NT platform have got an ability to use the RTX spreading in order to overcome the Windows NT disadvantage in real time tasks.

There should be noticed a tendency of SCADA-systems integration into the Complex Automation Systems of the enterprise. This enables precise and well-timed information at each level of production.

In SCADA-systems there used new technologies, the instrumentation devices are developed. This proves the aspiration and the ability of developing companies to constantly improve their products which is a very important advantage to choose this instrument even if not all of the technological decisions will be used in future.

Список литературы

1. Datasolution - Что такое SCADA. Проектирование SCADA. Cтруктура SCADA системы [Электронный ресурс]. – Режим доступа: http://datasolution.ru/chto-takoe-scada/, свободный (17.12.2014).

2. SCADA: что это? - ПромСофт Системы [Электронный ресурс]. – Режим доступа: http://www.promsoftsystems.ru/articles/scada.html, свободный (17.12.2014).

3. Журнал Мир компьютерной автоматизации - Системы диспетчерского управления и сбора данных (SCADA-системы) [Электронный ресурс]. – Режим доступа http://www.mka.ru/?p=41524, свободный (17.12.2014).

4. SCADA — диспетчерское управление и сбор данных. ООО "НовоСофт" [Электронный ресурс]. – Режим доступа http://www.novosoft.by/?page=b_scada, свободный (17.12.2014).

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