Computer automatic SCADA (monitoring and data acquisition) technology, also known as computer remote control (telemetry, remote control, remote communication and remote adjustment) technology, has been widely used in water supply and drainage industry, and has achieved good economic and social benefits, and has formed an industrial scale that benefits the society. How to guide the development of this technology, cultivate the water supply and drainage automation market, and then promote the development of automation industry is a very meaningful work. Therefore, this paper summarizes this technology in order to attract more attention.
Technical analysis of 1 and SCADA system
SCADA technology is based on 3CS (computer, communication, control and sensor). The above four technologies have developed rapidly recently, and new technologies and products are constantly introduced. At the same time, many old technologies and products have been ruthlessly eliminated. How to adopt new ideas, new technologies and new products to build a SCADA system suitable for water supply and drainage with powerful management functions, strong reliability, good on-site installation interface, convenient operation and maintenance and low price is the need of customers in water supply and drainage industry and the responsibility of SCADA system integrators. 3CS technology is described as follows:
computer technology
In recent years, computer PC technology has developed rapidly with the speed of a new generation every year. Powerful hardware platform (the main frequency is above 300M, CPU has MMX technology, memory 128M and above, hard disk 10G and high-speed CD? ROM and DVD? Luo Kaideng. ) Support the constantly updated Windows operating system, Windows software and network technology. The powerful PC system platform not only gets rid of the trouble of DOS operation, but also relieves the embarrassment of PC keyboard operation, which makes PC widely used and builds a high-function PC. SCADA system has created conditions. As we all know, in SCADA system, PC is mainly used as the main control or dispatching center. Recently, many domestic and foreign manufacturers have launched SCADA configuration software based on Windows. These software platforms can complete data acquisition related to water supply and drainage scheduling (providing communication drivers with various PLC or other intelligent devices, DDE function of dynamic data exchange, OLE technology, etc.). ), data processing, data display and data recording, etc. , and has a good graphical man-machine interface, MMI has the function of trend analysis and control. It provides a perfect means for optimizing water supply and drainage scheduling and saving energy and reducing consumption. The network function of PC provides many unexpected functions for the construction of multi-level dispatching SCADA system and participation in water plant management. Constantly updating the PC software and hardware platform in SCADA system does not account for a large proportion in the construction cost of SCADA system, but it has a great influence on improving the function and reliability of SCADA. It is cost-effective to strengthen the investment in the construction of dispatching center.
At present, the main problem is that there is no SCADA configuration software specially designed for water supply and drainage automation in China, and the general configuration software is expensive to purchase. The production is standardized, the price is moderate, and the function is suitable for SCADA configuration of water supply and drainage.
This software has a broad prospect, and it is also an important link in the SCADA construction of China water supply and drainage automation system in China.
2. Communication technology
The selection of communication technology and equipment is the most wonderful part of building SCADA system. Whether the design of SCADA system is reasonable is very important. Due to the integration of various communication technologies, it is very difficult and full of loopholes to try to explain by classification. Here, for the convenience of narration, we can only make a far-fetched classification.
1, network technology LAN WAN and Intranet
We can take network technology as a part of SCADA communication. Computer network interconnection and extension technologies based on TCP/IP, such as gateways, routers, bridges, repeaters and remote access services; Dynamic data exchange technology based on memory: Access technology based on open database constitutes control network and information. In fact, this part should be the management part of SCADA system, so it will not be described here.
2. Serial interconnection bus
RS？ 232、RS？ 485 and USB (Universal Serial Bus), the former two are well known, and USB is a newly introduced interface with high efficiency, plug and play and hot switching.
1.2.3, measurement and control bus standards such as Bitbus, Profibus, PROWAYC, PHOEBUS, HART, CAN, Dupline, L2, Modbus, SDS, ControlNET, FIP, SERCOS, FF, Lonworks, etc. The above-mentioned measurement and control bus standards are constantly infiltrating into SCA DA system, especially the communication between field, instrument and intelligent terminal is widely used.
1.2.4, wireless communication
Such as microwave, spread spectrum communication, satellite communication, iridium satellite communication, ultrashort wave communication, short wave communication, GSM, CDMA, two-way wireless paging, etc. Some of the above wireless communication is the application of public data network. Generally speaking, the most widely used communication is ultrashort wave 200MHz communication. In particular, two-way wireless paging is developing into water supply and drainage? The communication between pressure measuring terminal, water source well group and SCADA system of urban drainage network will play a very important role, and it is a reliable and cheap communication means.
1.2.5, wired communication
(1) PSDN ISDN and b? ISDN, especially b? The value-added services of ISDN integrated broadband data network and fttp project will greatly facilitate the construction of communication functions in urban water supply and drainage SCADA system, such as pressure measuring points, water source wells and sewage monitoring stations.
(2) Self-built wired network, generally using twisted pair as the medium. Various PLC manufacturers and communication manufacturers have formulated closed and open wired communication system protocols respectively, and have corresponding products, such as 6DC MODEM of Israeli RAD company, G enius bus of GE fanuc company, L2 of Siemens company, etc., which all provide good communication means for SCADA system. Widely used in SCADA system of water purification plant and sewage treatment plant.
1.2.6, carrier communication technology
Power carrier technology has been debated for many years. Recently, it was reported that Siemens has corresponding operator communication equipment for sale. I believe this technology will have a better prospect. SCADA used in water purification plants and sewage treatment plants can form a system without wiring.
1.2.7, optical fiber communication
Optical fiber communication is widely used in information communication because of its high bandwidth and high anti-interference. It also has the conditions for application in SCADA system. OZD485 produced by HIRSCHMANN, a German hessman company, is used for lighting? Electrical 485 protocol conversion CAN be applied to Partyline, SINEC, L 1, L2, Unitelway, GEbus, Modbus, BitBus, PROFIBUS, PNET, CAN and other protocols. Its multimode equipment only needs a few hundred marks. It can be seen that the application of optical fiber communication in SCADA has reached a practical level.
How to build a good SCADA system, the choice of communication technology is very important. Nowadays, various communication technologies are developing rapidly, and public communication technology has gradually established a reliable and cheap platform in the development of the market. SCADA system integrators should keep up with advanced technology in order to put forward the best communication scheme.
1.3, control technology
The control equipment referred to in this paper is the slave equipment of SCADA system, or the lower computer, remote terminal RTU and on-site measurement and control intelligent device, or special RTU, intelligent instrument, intelligent controller and PLC system. Control equipment,
Each SCADA system will have several sets, which have the greatest impact on the reliability and price of SCADA system. In the past ten years, the construction of water supply and drainage SCA DA system has formed many modes, such as PC PLC mode, PC single chip microcomputer mode and all-imported PC RTU mode.
1.3. 1, PC PLC mode
Here only the control part, that is, PLC. All manufacturers and various models of PLC are a system platform for serialized products, with their own closed networks and open interfaces. As far as the control function is concerned, PLC is a rigorous, convenient, easy to install, easy to program and highly reliable technical product. It provides high-quality hardware, high-level system software platform and easy-to-understand application software platform (user platform), which is very suitable for sequential logic control and many complicated calculations. And the bigger the scale, the more economical it is. In the SCADA system of water supply and drainage, such as tap water purification process control, sewage treatment process control, multi-pump system control of tap water secondary pumping station, multi-pump valve control in remote water transfer, etc., it has indisputable advantages. The shortcomings of PLC are also exposed in SCADA of water supply and drainage, which is manifested in the high price of analog data acquisition and insufficient manpower. Man-machine interface is expensive, and small and medium-sized PLC data can not realize the function of historical event recall (SOE), which limits its application in water supply and drainage SCADA system. In SCADA dispatching system, it is unbearable to use PLC as the terminal of pressure measuring point to monitor only one analog quantity, so it is necessary to use PC PLC to build SCADA system according to local conditions.
1.3.2, PC single chip microcomputer mode
Here, we only talk about the single-chip microcomputer (lower computer) related to control. For more than ten years, it has been the mainstream that single chip microcomputer constitutes the lower computer of SCADA system for water supply and drainage. From Z80 single-board computer to 803 1 8098, it is now the mainstream single-chip computer of 80C 196. Single-chip computers developed by scientific research units and companies constitute RTU of SCADA system, and the target design mode has never changed. In this way, the software of MCU RTU adopts a closed practice of mutual confidentiality (even within the same unit). This closure not only causes the disadvantage of difficult maintenance, but also destroys the resources of single chip microcomputer, and also causes the strange phenomenon that RTU of single chip microcomputer is not cheap. It is reported that so far, the price of each single-chip microcomputer device is several thousand yuan, while a single-chip microcomputer CPU is only a few tens of yuan. Of course, compared with PLC and imported RTU, single chip microcomputer is still the lowest price. Single-chip RTU is only suitable for pressure measuring point terminal, simple water source well control and simple environmental data acquisition. It should also be pointed out that at present, RTU made by domestic manufacturers with single chip microcomputer only supports wired rs? 232、RS？ 485 and wireless 200MHz communication, few people consider the interface application of other efficient communication protocols. So far, there is no commercial single chip microcomputer RTU product designed according to the system platform suitable for water supply and drainage SCADA. ? For more than ten years, the wide application of RTU single chip microcomputer has trained a large number of application and maintenance personnel for SCADA users. These personnel are valuable resources for the development of water supply and drainage SCADA and a part of water supply and drainage automation industry.
1.3.3, PC imports RTU mode.
It is reported that an imported RTU completes the data monitoring of a pressure measuring point, and some prices are as high as 60,000 yuan. This is a strange phenomenon, and I don't want to comment more.
1.3.4, mixed mode
At present, the practice of most systems is to form a hybrid SCADA lower computer with PLC and RTU.
Intelligent actuator for field measurement and control
There are many kinds of intelligent monitoring institutions in SCADA system. Frequency conversion speed regulating device is the most widely used device in water supply and drainage SCADA, which plays a very good role in improving water supply and drainage technology, strengthening process controllability and saving energy and reducing consumption. On-site measurement and control intelligence also includes pressure regulators and so on, which should be classified as sensing devices. Generally, intelligent devices for field measurement and control are controlled by SC ADA system. Some directly communicate with the host computer to form a system.
As the key work of SCADA system, control technology has not been standardized so far, let alone standardized products. In the concrete construction of SCADA system, it is mainly determined by the level, likes and dislikes and interests of contractors and designers. In addition, the continuous development and updating of technology is also one of the reasons for the lack of standardization and standardization. Standardizing and standardizing the lower computer platform of SCADA system is the key to build a high-quality and low-cost SCADA system.
1.4, sensor technology
Many sensors and actuators are installed in the production site layer of water supply and drainage SCADA system to complete data acquisition and control command execution in the production site of SCADA system.
Sensors can be divided into intelligent and non-intelligent types. Non-intelligence completes the conversion of standardized signal of electric quantity and the conversion of non-electric physical and chemical data to standardized signal of electric quantity. In addition to the work of the above-mentioned non-intelligent sensors, intelligent sensors also have the functions of upper and lower limit alarm setting, data display, simple digital logic control, PID adjustment and so on. Most of the latest intelligent sensors have some kind of field bus function, which can communicate with the upper computer or lower control unit of SCADA to form a SCADA system. ? Sensors commonly used in water supply and drainage SCADA mainly include: water level, pressure, flow, temperature, humidity, turbidity, residual chlorine, BOD, COD, voltage, current, power, electricity, cosφ, flowmeter, proximity switch, limit switch, water level switch, relay, etc. ? A few years ago, domestic sensors generally passed the standard, and the sensors of SCADA for water supply and drainage are still mainly from foreign sensor manufacturers.
Recently, a large number of domestic high-quality products have been introduced in the water supply and drainage sensor market. It can be said that the sensor is the highest and most successful link in SCADA localization.
Overview of SCADA market for water supply and drainage automation
Water supply and drainage automation market is composed of supply and demand sides. Suppliers are mainly composed of manufacturers engaged in SCADA system integration and related, and demanders are water supply companies, sewage treatment plants, large factories and mines related to water supply and drainage and government agencies.
Demand-side market composition
There are more than 600 cities in China, and each city has its own water supply and drainage automation market. There are also hundreds of power stations, large-scale joint ventures and vast towns and villages, which constitute a broad water supply and drainage automation market. The buyer is the driving force of the market, and the driving force for the buyer to purchase SCADA system for water supply and drainage is roughly as follows:
2. 1. 1, legal reasons
(1) Water supply (tap water): Limited by the Water Law, it must meet the standards. SCADA system is one of the important means to achieve water quality standards.
(2) Drainage: The state has formulated relevant laws, and sewage must be discharged up to the standard. SCADA system is one of the important means to achieve the discharge up to the standard.
2. 1.2, economic reasons
A SCADA system with complete system design, careful and scientific equipment selection, good system integration and reliable quality can bring good economic benefits to the demand side of drainage SCADA in terms of staff reduction, energy saving, consumption reduction and strengthening management.
2. 1.3, corporate image
Many users consider the company image to establish SCADA system.
2. 1.4, investor requirements
At present, many water purification plants, sewage treatment plants and large factories and mines are all invested by foreign investors, and the SCADA system has been built in the original design, which is required by the investors.
2.2. The composition of the supply-side market is bound to complicate the supply-side market in the face of the vast demand-side market and the complicated reasons for the buyer's purchase. Suppliers are the driving force and participants in market competition. The market power of suppliers is classified according to the primary market composed of equipment suppliers and the secondary market composed of system integrators.
2.2. 1, SCADA equipment supply primary market
The primary market includes computer and peripheral hardware suppliers; Computer and controller software equipment suppliers; Communication equipment suppliers; Control equipment suppliers (PLC, etc. ); Suppliers of sensors and actuators; Cable and cabinet suppliers; Electronic equipment suppliers; Power suppliers, etc.
2.2.2. Secondary market composed of system integrators (automation engineering contractors)
(1) professional agent integration of foreign SCADA system;
(2) Engaged in system integration of system interconnection;
(3) Engineering contractors who independently develop software and hardware devices by scientific research institutions;
(4) SCADA system integration contracted by the buyer;
(5) Subcontractors.
Among the system integrators, there are many powerful developing companies and many units that are like a duck to water. The automation systems built by these integrators are very different, so I won't comment here.
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