Principles of constructing automated control system scada systems. SCADA systems

The highest level of any automated system is, of course, a person. However, in modern technical literature, the upper level is understood as a complex of hardware and software, performing the role of a semi-automatic dispatcher node of the process control system, the core of which is a PC or more powerful computer. The human operator enters the system as one of the functional links of the upper management level. This approach has both positive and negative sides. The positive point is that the operator’s responsibilities in this case are predetermined, and he is not required to have detailed knowledge of the technological process. In other words, not only a qualified technologist can manage the process. The negative aspects are a consequence of the fact that management flexibility decreases due to a decrease in influence on the process.

In this regard, process control system developers have to take into account additional requirements. It is necessary not only to take into account the hardware component of the process, not only to select the operating modes of the equipment, but also to develop reliable and correctly operating software. Certainly, best option- this is such an organization of work when the same group of developers is responsible for the technological process map, and for the selection and debugging of equipment, and for software development. In this case, developers must be equally strong in the technology of a specific process, in the use of special equipment, and in writing complex controls, service and communication programs. However, selecting such a team can be difficult.

To simplify the development of the software component of the process control system, the so-called MMI (Man-Machine Interface) and SCADA (Supervisory Control and Data Acquisition) programs are now used. The use of these packages allows for automated development of automated control system software; carry out real-time monitoring and control of the technological process; receive and process information about the process in a convenient form.

The most exciting and at first glance simple stage when using SCADA systems is modeling the technological process on the monitor screen. Graphic similar Windows interface The system is intuitive and simple. Installation of actuators, electric motors, valves, tanks, pipelines and other equipment used in the process is just a click away. Linking equipment parameters to process needs is also easy and can be done in a few clicks. Global and “tactical” process parameters are entered into forms organized in the form of tables or databases. Standard process controls are installed, and control sensors are polled. Then you can click on the “Start” button and start the technological process. This happens in theory or when demonstrating the capabilities of a particular SCADA system. But in practice everything is more complicated.

The development of process control systems using SCADA systems, regardless of the process and specific SCADA package, involves the following main steps:

• development of the system architecture as a whole. The process control system is built in a client-server architecture. The functional purpose of individual automation units and their interaction is determined;
• creation of an applied control system for each automation node (or rather, an algorithm for automated control of this node);
• analysis and elimination of emergency situations;
• solving issues of interaction between levels of process control systems; selection of communication lines, exchange protocols; development of algorithms for the logical interaction of various subsystems;
• resolving issues of possible expansion or modernization of the system;
• creation of operator interfaces;
• software and hardware debugging of the system.

All these issues must be resolved at the stage of designing and creating the top level of the process control system, otherwise situations may arise when the various functional modules of the technological process will be difficult to link with a control system that is unified in ideology and technical implementation. Using the SCADA system allows you to quite successfully carry out all of the above stages of design and debugging.

How SCADA systems work

SCADA packages consist of several software blocks: access and control modules, alarms, real-time databases, databases and input/output and emergency modules.

The main requirement for SCADA systems is correct operation in real time. Moreover, the main priority in transmission and processing is given to signals coming from or to the technological process and affecting its progress. They take precedence even higher than disk access or operator actions such as moving the mouse or minimizing windows. For these purposes, many packages are implemented using real-time OS operating systems, but recently more and more developers are creating their SCADA products using Microsoft platform Windows NT, integrating RTX (Real Time Extension) hard real-time subsystems into it. With this approach, you can use Windows NT as a single OS when creating multi-level systems, use standard features Win32 API and build integrated Information Systems- ASUP.

Data sources in SCADA systems can be the following.

• Drivers for communication with controllers. The reliability of communication drivers is very important. Drivers must have means of protecting and restoring data in case of failures, automatically notify the operator and the system of loss of communication, and, if necessary, sound an alarm.
• Relational databases. SCADA systems support protocols independent of the type of database, thanks to which most popular DBMSs can act as a data source: Access, Oracle, etc. This approach allows you to quickly change the settings of the technological process and analyze its progress outside of real-time systems, in various ways , programs specially created for this purpose.
• Applications that contain a standard DDE (Dynamic Data Exchange) interface or OLE (Object Linking and Embedding) technology that allows you to include and embed objects. This makes it possible to use even some standard office applications, such as Microsoft Excel, as a data source.

The input of incoming and output of transmitted data is organized as a system of special functional blocks. Current information about the process is stored in special I/O databases. Input blocks receive information and transform it into a form suitable for further analysis and processing. Processing blocks implement monitoring and control algorithms, such as PID control, delay, summation, statistical processing; Boolean algebra operations, etc. can be performed on digital data. Output blocks transmit a control signal from the system to the object. For communication with objects, widely used interfaces RS-232, RS-422, RS-485, and Ethernet are used. To increase the transmission speed, use various methods data caching, which eliminates congestion on low-speed networks. In other words, if two different clients simultaneously request the same data from the server, it sends not two requests to the controller, but only one, returning data from the cache to the second client.

Perhaps the most important point when creating an automated process control system is the organization of a control system that would ensure reliability and prompt handling of emergency situations both in the control system itself and in the technological process. Alarm signaling and processing of emergency situations in the technological process in most SCADA systems are allocated to a separate module with the highest priority. The reliability of the control system is achieved through hot backup. You can reserve everything: the server, its individual tasks, network connections and individual (or all) connections to the equipment. Redundancy occurs according to an intelligent algorithm: in order not to create double the load on the network, the main server interacts with the equipment and periodically sends messages to the backup server, which stores the current system status in memory. If the primary server fails, the backup server takes over and operates until the primary server starts working. Immediately after this, the databases of the main server are updated with the data of the backup server and control returns to the main server.

All SCADA systems are open for further expansion and improvement and have built-in languages ​​for these purposes high level, more often Visual Basic, or allow the connection of program codes written by the user himself. In addition, developments from other companies can be connected to the systems, ActiveX objects, standard DLLs Windows. To implement these technologies, special tools and a specialized interface have been developed.

A SCADA system can be integrated with a variety of networks: other SCADA systems, enterprise office networks, recording and signaling networks (for example, security and fire alarms), etc. For efficient work In this heterogeneous environment, SCADA systems use standard NETBIOS and TCP/IP protocols. The mere mention of the TCP/IP protocol already indicates that SCADA systems can also work on the Internet, especially since the transfer of operational and static information about the process to Web sites is becoming increasingly important.

In conclusion, I would like to say that the concept of process control systems is initially broader than SCADA. When in the literature they sometimes talk about SCADA systems, meaning process control systems, this is not entirely correct. SCADA were developed specifically as systems that allow the operator to provide information services on upper level process control. But they cannot provide fully automated control from top to bottom, if only for the simple reason that it is only software, installed on personal computer. And any technological process requires, in addition, a variety of specific equipment and it takes place in real life, and not in a virtual environment.

However, the current practice of building automated systems controls of sufficient complexity indicates that the use of SCADA systems in the design of process control systems significantly simplifies the lives of developers and allows them to organize reliable and high-quality control during the operation of systems.

Supervisory Control And Data Acquisition (SCADA)

SCADA system is a tool program that ensures the creation software to automate monitoring and control of the technological process in real time. The main goal of a program created using SCADA is to give the operator managing the technological process full information about this process and the necessary means to influence it.

MAIN TASKS OF THE SCADA SYSTEM:

• Collecting data from sensors and presenting them to the operator in a form convenient for him, including graphs of changes in parameters over time;
• Remote control of actuators;
• Inputting tasks for automatic control algorithms;
• Implementation of automatic monitoring and control algorithms (most often these tasks are assigned to controllers, but SCADA systems are also capable of solving them);
• Recognizing emergency situations and informing the operator about the state of the process;
• Generating reports on the progress of the process and production of products.

Not only the efficiency of process control, but also its safety depends on the reliability, speed and ergonomics of the SCADA system.

WHAT SCADA COMPONENTS ARE MOST IMPORTANT IN OPERATION AND WHY?

Specialists from the control system department of an industrial enterprise for the production of soda claim that they mainly use components such as monitoring and control, archiving of process parameters, messages, and a reporting subsystem.

Monitoring and control, in fact, is what a control system is installed for. Archives of parameters, messages and reports are necessary for assessing and analyzing the technological process, operator actions, etc. Also important for them is one of the basic SCADA tools - differentiation of access rights to control by levels (operator, technologist, process control engineer).

Due to the trend towards integration of process control systems and enterprise management systems, there is an increasing need to use SCADA as a data source for higher-level systems. Some SCADA can act both as a server for consolidating all process data and as a server for generating reports based on this data.

If the control system is built on the basis of a PLC from one manufacturer (for example, Siemens SIMATIC), then data exchange between the controllers and SCADA occurs using built-in communication protocol drivers. Some OEM-independent SCADA systems offer a set of drivers for many (but not all) controllers and smart devices on the market. Most universal method interaction is the use of drivers developed in accordance with the OPC standard. Such OPC servers can be developed by controller manufacturers or independent developers, and used in conjunction with any SCADA system. To work effectively with OPC servers, SCADA must use them directly, using the “OPC in the system core” technology, and not through intermediate interfaces. Some SCADA are vertically integrated: they include programming systems for freely programmable controllers. They also use internal drivers to communicate with the controller. Such SCADAs allow you to create a control system using equipment from different manufacturers.

SYSTEM LEVELS USING SCADA

Process automation systems are usually divided into 3 levels: lower, middle and upper. Above them is the level of production management as a whole.
Lower level– these are the sensors and actuators themselves
Average level– controllers. At the middle level what happens:

• receiving input data;
• primary data processing;
• automatic generation and issuance of control actions on actuators;

Top level – this is the SCADA level. At this level what happens:

• collection, processing and storage of information obtained at the middle level;
• visualization of current and archived information in a form convenient for the operator (mnemonic diagrams, graphs, trends, message logs);
• entering operator commands;
• generating reports on the results of the technological process;
• exchange of information with the upper level.

ENTERPRISE MANAGEMENT

Enterprise management is carried out at two levels:
MES (Manufacturing Execution Systems) is a real-time production management system. This level is used to plan production tasks for technological processes, build summary reports, and in-depth process analysis (for example, forecasting, building an energy and material balance, etc.). SCADA tools can also be used for these purposes.

ERP (Enterprise Resource Planning) is a system for automated management of administrative, financial and administrative activities of an enterprise. At this level, other specialized systems are used, for example, SAP R3.

SCADA FUNCTIONS

■ Mnemonic diagrams
Mnemonic diagram is graphic image(using built-in SCADA graphic editor) technological diagram with visualization of sensor values, state of actuators and other parameters. For visualization, not only the display of values ​​in the form of numbers and inscriptions is used, but also the change in the visual properties of the displayed graphic objects. For example, the level of liquid in a container changes, and its color changes depending on the temperature (dynamization). Actuators can not only show their state with some graphical sign (for example, color), but also clearly show their work - for example, by the rotation of pump blades, the movement of a conveyor belt, etc. (animation).

■ Archives
The SCADA data received from the controllers is stored in archives. The data can be pre-processed (filtered, averaged, compressed, etc.). Often, not regular recording is used, but recording by change using a sensitivity threshold (“dead zone”). The storage duration is configured in SCADA individually for each parameter and can be up to several years.

■Trends
A trend is a graphical display of changes in a parameter over time. Trends in SCADA systems can show changes in a parameter over the entire duration of its storage in the archive. The operator is given the opportunity to change the scale of both time and the parameter itself. In developed systems, the trend has various tools built into the trend for analyzing the graph, comparing it with a setpoint or other parameter, smoothing or filtering, marks on the event graph (for example, violation of boundaries) or memory bookmarks, and much more.

■ Tables
It is often more convenient for a technologist to view archives not in graphical form, but in the form of tables. Typically, these tables can not only be viewed, but also exported to other systems.

■ Charts
Typically, SCADA allows you to view the dependence of some parameters on others, also over time. Although this function is less in demand among technologists than trends.

■ Histograms and charts
Another common way of representing parameters is histograms (bar charts).

■ Messages
Messages are text strings, which inform the operator about events at the facility in the sequence in which these events occur. They pop up on the screen or are displayed in a specially designated area.

■ Message logs
Message logs are used to display lists of messages in the order they appeared and were saved to the archive. As a rule, different log instances are used for different process zones, different message categories, and different priorities.

■ Access rights control
In order for the operator to perform certain actions, he must be granted the appropriate rights by the administrator - for example, the right to control the actuator, or the right to change the task of the regulator. At the beginning of the shift, the operator registers in the system, and it allows him to perform only those actions that are allowed to him by the administrator.

■Operator activity log
Technological process control is a very important task, therefore all operator actions are recorded for control in a special log, which can be analyzed in case of emergency situations.

■ Generating a report
A convenient report development environment allows you to easily and quickly prepare formatted and information-rich reports.

SCADA SYSTEM CHARACTERISTICS

• Operating system compatibility;
• Full functionality;
• Openness;
• Scalability;
• Support for industrial protocols (own driver subsystem);
• Compatible with OPC standard (DA, HDA, UA);
• Internet access support;
• Database support;
• Built-in programming languages;
• Safety features and reliability;
• Integration into control systems;
• Technical support;
• Ease of development and development;
• Ease of maintenance;
• Price.

FOREIGN SCADA SYSTEMS

The most popular foreign SCADAs in Russia are:

– WinCC (Siemens, Germany);
– InTouch (Wonderware, USA);
– RSView32 (Rockwell Automation, USA);
– Genesis64 (Iconics, USA);
– Vijeo Citect (Schneider Electric, France).

DOMESTIC SCADA SYSTEMS

The most popular domestic SCADA models:
– MasterSCADA (InSAT, Moscow);
– TRACE MODE (AdAstra, Moscow);
– Krug2000 (Krug, Penza).

Unlike most Western SCADAs, all Russian ones contain built-in controller programming tools using the languages ​​of the IEC61131-3 standard, including the language of functional blocks. Moreover, if SCADA itself is designed to work in Windows environment on PC-compatible computers, the executive system for the controllers can also run on Logix other platforms, for example, Linux on an ARM processor.

The OPC standard is supported by all of the listed systems, however, in the “Trace Mode” system the emphasis is on the use of its own drivers, and MasterSCADA, although it supports the use of drivers, is based on the “OPC in the system core” technology and offers a separate tool package for the development of OPC servers .

Comparative characteristics of foreign and domestic SCADA

All modern SCADA, both domestic and foreign, have full functionality for this class of programs, so their comparison according to the list of functions in last years lost its meaning. The main advantage of Russian SCADA is their initial focus on the Russian market (Russian-language, not translated documentation, technical support, price level). It can be concluded that for each enterprise or even application it is advisable to compare several SCADAs, both in terms of price and capabilities. Almost all SCADA have trial version, which allows you to check its suitability for the problem being solved.
Editorial office "KIPinfo"

Electronic magazine “KIPinfo” No. 17 2013

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SCADA (supervisory control and data acquisition, supervisory control and data acquisition) is a software package designed to develop or ensure real-time operation of systems for collecting, processing, displaying and archiving information about a monitoring or control object. SCADA can be part of an automated process control system, ASKUE, environmental monitoring system, scientific experiment, building automation, etc. SCADA systems are used in all sectors of the economy where it is necessary to provide operator control over technological processes in real time.

The main function of SCADA systems is the creation of a human-machine interface, i.e. The SCADA system plays two roles at once - as an HMI and as a tool for its creation. Subsystems included in the SCADA system:

drivers or I/O servers – programs that provide SCADA communication with industrial controllers;

real-time system – a program that ensures data processing within a given time, taking into account priorities;

human-machine interface - a tool that presents data about the progress of a process to a human operator, which allows the operator to monitor and manage the process;

logical control system – a program that ensures the execution of user programs (scripts) of logical control in the SCADA system. A set of editors for their development;

real-time database – provides storage of process history;

alarm management system - a program that provides automatic monitoring of process events, classifying them as normal, warning or emergency, as well as processing events by an operator or computer.

The role and place of scada systems in the automated process control market

By application, SCADA systems can be divided into two groups:

use of methods artificial intelligence to solve support and decision-making and management problems;

processing methods and presentation of information knowledge-based.

The first group includes systems that implement traditional functions of monitoring and process control:

maintaining a real-time database;

performing calculations;

graphical representation of data and parameters in the form of mnemonic diagrams, graphs, diagrams, etc.;

warning alarm;

archiving information;

generating reports.

This group includes products like: RTAP/Plus (HewlettPackard), Monitrol\UX (Hilco), PMIS (Bradley-Ward), Simplicity (GE Fanuc), etc.

The functions of the systems of the second group include intelligent information support for the human operator when managing processes. These features include:

situational analysis of the state of the control and management object;

prompt search for operator-manager actions in the event of abnormal and critical situations;

diagnostics of the condition of technological equipment;

diagnostics of the state of the technological process;

logical analysis of events;

logical analysis of anomalous situations;

forecast of process behavior over time and others;

protection from actions of operational personnel unauthorized by technological regulations;

maintaining real-time databases and knowledge;

maintaining hypertext databases of operational and regulatory knowledge.

Examples of these systems are the foreign system G2 (Gensym, USA), and the domestic system “SPRINT-RV” (Russia), which include not only tools for designing and testing domain models, but also tools for intelligent information support for real-time decision making . The systems of these two groups can be mutually complementary, but if the system of the first group is the basis of modern management systems, then knowledge-based systems are not often used for many reasons.

Some of the main reasons are:

the technology for creating systems that are based on knowledge is not sufficiently formalized and requires the involvement of highly qualified engineering specialists, knowledge and expensive experts, which ultimately leads to significant financial and time costs. Therefore, systems of this class are created only when their use promises very large material benefits;

Knowledge-based systems are developed mainly as systems whose knowledge model cannot be complete, which does not always allow them to be included in the main monitoring and management tools. They are used as information and consulting tools.

These problems can be solved in the following way - with the help of monitoring/control and methods, knowledge-based systems should be created using a single, highly automated technology and form a single whole. Such integrated technology is provided by the SPRINT-RV system, which implements both traditional monitoring/control functions and intelligent technologies for operational decision support.

SCADA systems are designed for monitoring and supervisory control of a large number of remote objects (from 1 to 10,000, sometimes at a distance of thousands of kilometers from each other) or one geographically distributed object. Such facilities include oil pipelines, gas pipelines, water pipelines, electrical distribution substations, water intakes, diesel generator points, etc.

The main task of SCADA systems is to collect information about many remote objects coming from control points and display this information in a single dispatch center. Also, the SCADA system must provide long-term archiving of the received data. The dispatcher often has the ability not only to passively observe the object, but also to control it, reacting to various situations.

Tasks of SCADA systems:

• exchanging data with the device (communication device with the object, that is, with industrial controllers and input/output boards) in real time through drivers;
• real-time information processing;
• displaying information on the monitor screen in a form understandable to humans;
• maintaining a real-time database with technological information;
• alarm signaling and alarm management;
• preparation and generation of reports on the progress of the technological process;
• providing communication with external applications (DBMS, spreadsheets, word processors etc.).

Structure of SCADA systems

Any SCADA system includes three components: remote terminal(RTU - Remote Terminal Unit), control center (MTU - Master Terminal Unit) and communication system (CS - Communication System).

The remote terminal connects directly to the controlled object and carries out control in real time. Such a terminal can serve as either a primitive sensor that collects information from an object, or a specialized multiprocessor fault-tolerant computing complex that processes information and controls in real time.

The control center performs data processing and high-level control, usually in quasi-real time. It provides a human-machine interface. MTU can be either a single computer with additional devices for connecting to communication channels, or a large computing system or a local network of workstations and servers.

A communication system is required to transfer data from RTU to MTU and vice versa. The following data transmission channels can be used as a communication system: leased lines, radio networks, analog telephone lines, ISDN networks, cellular networks GSM (GPRS). Devices are often connected to multiple networks to ensure reliable data transfer.

Features of the control process in SCADA systems

• In SCADA systems, the presence of a person (operator, dispatcher) is mandatory.
• Any incorrect impact can lead to failure of the control object or even catastrophic consequences.
• The dispatcher typically has overall responsibility for managing the system, which, under normal conditions, only occasionally requires adjustments to achieve optimal performance.
• Most of the time, the dispatcher passively observes the displayed information. The active participation of the dispatcher in the control process occurs infrequently, usually in the event of critical events - failures, emergencies and emergency situations, etc.
• The operator's actions in critical situations can be strictly limited in time (several minutes or even seconds).

Protection of SCADA systems

There is an opinion among some users of SCADA systems that if the system is not connected to the Internet, it is thereby protected from cyber attacks. Experts disagree.

Physical isolation is useless against attacks on SCADA systems, says Faizel Lakhani, security expert information resources. In his opinion, physically isolating systems is tantamount to fighting against windmills.

The opinions of Russian experts regarding the security of automated process control systems and SCADA systems are consonant. As ICS security issues have become the focus of everyone's attention, some manufacturers of security solutions have begun developing products aimed at countering threats to industrial information systems (such products, in particular, may include secure operating system- an environment for the operation of only trusted applications).

Some companies have begun to prepare analytical materials on these issues, making attempts to assess the state of process control systems from a security point of view. The reaction to these initiatives from specialists working with industrial systems is ambiguous and not always favorable. An outside observer can conclude: between operators