SCADA system tutorial - SCADA system

　　Chapter I: SCADA system

　　1.1 significance of SCADA system

　　1.2 composition of SCADA system

　　1.3 master station system of SCADA

　　1.4 communication system of SCADA

　　1.5 remote terminal unit of SCADA

　　Chapter II: SCADA system

　　2.1 overview

　　2.2 system hardware composition

　　2.3 system software composition

　　2.3.1 protocol interface module

　　2.3.2 real time database

　　2.3.3 graphical interface

　　2.3.4 graphic tools

　　2.3.5 Alarm

　　2.3.6 historical data

　　2.3.7 network release

　　2.3.8 work stage division of master station system

　　2.4 upper layer application of SCADA software

　　Chapter III: SCADA Communication System

　　2.5 overview

　　2.6 wired system

　　2.7 wireless system

　　2.8 network system

　　Chapter IV remote terminal unit (RTU)

　　2.9 overview

　　2.10 remote signal

　　2.11 remote command

　　2.12 remote measurement

　　2.13 remote regulation

　　1.1. Significance of SCADA system

　　SCADA is the abbreviation of supervisory contrai and data acquisition system. It is a data acquisition, monitoring and control system for the production system with long distribution distance and scattered production units.

　　Understanding the production situation is the basis for the implementation of scientific production. If the production process is closely distributed, the method of local control can be adopted, including local wiring, local monitoring and local control. For complex process production, DCS system control is more often used, and PLC or professional controller is also used. For the production links that are distributed far away, such as several kilometers, tens of kilometers, hundreds of kilometers or even thousands of kilometers, such as substations, natural gas pipelines, oil fields and tap water pipe networks, with the development of technology, people have slowly developed a remote acquisition, monitoring and control system, called SCADA system.

　　SCADA system differs from other systems in that:

　　Widely distributed area

　　The master station is far away from the control object

　　The working conditions of the monitoring terminal are harsh

　　The communication system is complex and changeable

　　The communication system does not guarantee reliable transmission

　　1.2. Composition of SCADA system

　　SCADA system mainly consists of three parts,

　　The master station, communication system and remote terminal unit. The master station generally adopts advanced computers with good graphic support. Now PC computers and windows systems are mostly used. In history, many systems used UNIX system and xwindows graphical interface. The number of possible sub stations of a master station ranges from dozens to hundreds or thousands.

　　The communication system is very complex. Wired includes audio cable, carrier cable, optical fiber, power carrier, etc., while wireless includes radio, satellite, microwave, etc. There are also many kinds of rtuortelecontrol. A large system consists of many cabinets, and a small system may be a small box.

　　1.3. Master station system of SCADA

　　In the past, the master station of SCADA system was composed of many famous systems, which were based on UNIX operating system family and xwindows graphical interface.

　　With the development of computer system, especially the development of PC, PC and the operating system running on PC are playing a more and more important role.

　　The huge master station system generally includes the following contents:

　　The communication front-end system is mainly responsible for analyzing various protocols and completing communication interface data processing, including data forwarding. Including front-end computer, serial port pool or modem pool, rack, lightning protection measures and network interface.

　　The real-time database system mainly includes the server running the real-time database.

　　Engineer workstation, responsible for system configuration, picture production and various maintenance of the system.

　　The production dispatching workstation is the main user of the monitoring system, which can display the screen, browse the screen, and realize various alarms.

　　Various monitoring workstations are mainly used for particularly large systems. When several people are unable to monitor, they will be set as needed

　　Set up various monitoring workstations, and each workstation has staff.

　　The historical database server is the server for SCADA system to save historical data. Web server is a popular trend of SCADA master station system. As long as users are equipped with browser software, they can get the corresponding information

　　Authorization, you can access the corresponding data he cares about.

　　The upper application workstation is mainly used for mining real-time data and historical data. In power system, such as power flow analysis, load forecasting, accident recall, power grid stability analysis, energy management and so on. In the water industry, it includes pressure loss analysis of pipe network, economic analysis of pipe network, leakage analysis of pipe network, etc. In oil production engineering, including indicator diagram display, indicator diagram analysis, pump condition analysis, indicator diagram production calculation and so on.

　　As a SCADA master station system, a large system may have dozens, hundreds of workstations and multiple servers. In order to ensure the reliability of the system, double front-end system, multi server system and two networks are adopted. However, for a simple SCADA master station system, there may be only one computer running a set of software.

　　SCADA systems for various applications can be said to be mostly the same or similar. However, each industry has the characteristics of each industry, and each industry cares about different things. For example, the power industry is very concerned about the voltage and current power of each line, while the water industry is not particularly concerned about these data, but about the pressure and flow of pipelines. This forms a system of different industries. There are also general man-machine interfaces, but this interface generally can not meet the special needs of various industries.

　　1.4. SCADA Communication System

　　SCADA Communication system is the most colorful, and there are many communication modes that many people have never heard of. The general classification can be divided into two categories: wired and wireless. However, with the development of communication technology, communication methods based on various networks are also developing rapidly. This communication method is difficult to be attributed to the category of wired or wireless, so it is also a separate category.

　　There are many wired modes: audio cable, overhead open line, carrier cable, coaxial cable, optical fiber, power carrier, etc. On line transmission is generally divided into baseband transmission and modulation transmission. Baseband transmission transmits digital signals on the medium, which may also undergo signal changes. The modulation and demodulation transmission shall go through the transmission of analog-to-digital conversion. Many media can be transmitted as baseband or modulation.

　　Wireless means mainly include radio, microwave, satellite, light, sound wave and other means.

　　The network mode is that the communication system is built on a computer network, such as frame relay and ATM, IP network, this communication mode may be wired or wireless, and even cross wireless and wired for many times. Its performance is also significantly different from wired and wireless systems. For example, the bit error, the size of the message and the topology of the system are not considered, but the network delay may be large. The transmission of SCADA system data through GPRS network or CDMA is a typical example.

　　1.5. Remote terminal unit of SCADA

　　SCADA system remote terminal unit has a special vocabulary RTU. It is now called telecontrol in terminology. RTU generally consists of communication processing unit, switching value acquisition unit, pulse value acquisition unit, analog value acquisition unit, analog value output unit, switching value output unit and pulse value output unit. There are other interface modes, such as tap of power transformer, gray code interface of Meteorology and hydrology

　　BCD code interface, etc.

　　Remote communication is generally installed with RTU, which is convenient for wiring.

　　In addition to the current RTU to complete its own data acquisition and protocol processing, it also needs to complete the interface and protocol conversion with various ied devices.

　　Moreover, the communication processing unit of RTU is becoming more and more powerful, while the corresponding acquisition work is gradually weakened and replaced by various ied devices.

　　The biggest development of RTU in China's power system is to directly calculate the voltage, current, active power, reactive power, power factor, frequency and harmonic of the line with AC sampling algorithm, which replaces the traditional power transmitter, reduces the cost, reduces the wiring complexity, reduces the error link and improves the accuracy. Now, the equipment integrating protection, telecontrol and measurement has appeared, and the traditional telecontrol has basically withdrawn from the historical stage.

　　The development in other industries is limited to the author's knowledge and cannot write more.