Thermal power plant instrument control system of "West Power Transmission Project"

Introduction In order to implement the Central Western Development Strategy and Sustainable Development Strategy, China's power industry has entered a new phase of building a nationwide unified power grid with the opportunity to build the Three Gorges Power Grid, and promote the interconnection of large regions and then build a nationwide unified dispatch. "West Power Transmission to the West" is an objective requirement of China's distribution of resources and productivity, and it is also an important part of the development of the western region. As “West-East Electricity Transmission” is a long-term sustainable development strategy of the country, its power transmission planning path and related power supply construction are constantly changing due to various factors, so the vast amount of its projects, the high investment quota, and the engineering cycle The length is difficult to estimate accurately. In order to meet the rapid growth of electricity demand in Guangdong Province in the future, the country decided to increase its efforts to send electricity to Guangdong. The “10th Five-Year Plan” mainly transmitted power to Guangdong from three regions in Yunnan, Guizhou, and Shanxia, ​​reaching 10 million kilowatts, and continued to increase power transmission during the Tenth Five-Year Plan period and later with the construction of Longtan Xiaowan and other power stations. Strength. The south will be built into a main grid consisting of multiple back-and-forth direct transmissions from the west to the east. The main grid of the West-East Power Transmission is the national development focus during the “10th Five-Year Plan” period, and the related thermal power construction and instrument control system will be the focus of this article.

1 “West to East Power Transmission Project” Overview China’s coal resources are mainly “Three West” (Shanxi, Shaanxi, and Mengxi), and hydropower resources are mainly distributed in the southwest (Lijiang River, Nujiang River, Hongshui River, Upper Yangtze River, Yarlung Zangbo River), In the northwest (upper reaches of the Yellow River), the primary and secondary energy sources in eastern China, southern China, and Central China, where the economy is relatively developed, are relatively lacking.

There are great imbalances in the distribution of energy resources and economic development in the four southern provinces (regions). Yunnan and Guizhou provinces in the west are rich in energy resources, accounting for 91% of the total in four provinces and regions, but their economic development is relatively backward. GDP Only about 20%, while the eastern part of Guangdong Province is very poor energy resources, but the level of economic development is high, although Guangxi has rich hydropower resources, but the coal resources are very poor, Guangdong and Guangxi Provinces accounted for only 9% of the four provinces, but GDP accounted for About 80% of the total amount of four provinces and regions.

The national power grid has formed three major transmission channels in the north, middle, and south due to the “West-to-East power transmission,” and the north-south and south-south networks have been promoted by the mutual supply of North and South, thus creating a unified national grid.

The North Channel includes Northeast China, North China, Shandong, and Northwest China Power Grid. The north-west power transmission from the west to the east is mainly the transmission of power from the west to the east of the North China Power Grid, which will shut down the thermal power in Shanxi and Mengxi to Beijing-Tianjin-Hebei and Shandong Power Grid in the east; and give full play to the hydropower in the upper reaches of the Yellow River in the Northwest and the areas in Shaanxi and Ningxia. The advantages of coal resources are transmitted to Beijing-Tianjin-Hebei and Shandong Power Grid in the east.

The Middle Passage includes East China, Central China, Chuanyu, and Fujian Power Grid, starting with the transmission of power from the Gezhouba Power Station to Shanghai, the completion of the Three Gorges Project and the completion of the Three Gorges Project to form the middle track of the eastward transmission of the Three Gorges Power; the long view will be sent to East China through the development of the Jinsha River and the Sichuan Hydropower Base. , Central China, and Fujian have further expanded.

The South Channel includes the power grids of Guangdong, Guangxi, Guizhou, Hainan, and Hong Kong and Macau. It has gradually strengthened with the development of the Tianshengqiao, Longtan Bay, Goupitan, and Nuozhadu hydropower stations and the Guizhou and Yunnan Hangkou thermal power plants. The overall structure of the South-Route West-East Power Transmission is the power development of the Nankou River, Beipan River, Hongshui River, and the Hangkou Thermal Power Plants in the two provinces of Guizhou, Wujiang, Yunnan, Minjiang, and Guangxi, Guizhou, and Fujian. Come out to Guangdong to send electricity.

2 Transmission of 10 million kilowatts to Guangdong Project Overview Since the Southern Interconnected Power Grid began its networking operation in August 1993, it has realized the transmission of seasonal energy from the Tianshengqiao Hydropower Plant, Yunnan and Guizhou to Guangdong. By the end of September 2000, a total of 23 billion kilowatt-hours of electricity had been sent to Guangdong. At present, China Southern Power Grid has two 500KV transmission lines through Tianshengqiao to send electricity to Guangdong, and the maximum transmission power reaches 1.28 million kilowatts.

According to the prediction of the relevant departments, during the “10th Five-Year Plan” period, the average GDP growth rate of Guangdong’s national economy was 9%. Considering the power elasticity coefficient of 0.8, the average growth rate of Guangdong’s power load was 7.2%. If the forecast is based on the maximum load of 23 million kilowatts in 2000, during the “10th Five-Year Plan” period, the Guangdong Power Grid will increase its load by 9.56 million kilowatts, requiring an increase of 11.5 million kilowatts. Considering Guangdong's "Ninth Five-Year Plan" to carry forward the "10th Five-Year Plan" with a scale of 2.96 million kilowatts under construction, deduction of small thermal power units will require about 10 million kilowatts of electricity transmission outside the province.

2.1 Power Supply Project 1. Tianshengqiao Hydropower Station Guangdong Guangdong 1.68 million kilowatts 2. Guizhou Power Transmission Guangdong (4 million kilowatts power project)

(1) Hydropower:

Hongjiadu Hydropower Station installed 3.18 million kilowatts.

Wujiangdu Hydropower Station expands 2 x 250 kilowatts.

Suofengying Hydropower Station installed 4 x 135,000 kilowatts.

(2) Thermal power projects under construction:

Xi 4×135,000 kilowatts of hydro power plants and 2.2 million kilowatts of power plants in Panxian.

(3) New thermal power project (first batch):

Yubei Power Plant 2×300,000 kilowatts.

The second phase of Anshun Power Plant is 2×300,000 kilowatts.

Nayong Power Plant 4×300,000 kilowatts.

The demonstration of desulphurization of expensive electric flue gas desulphurization (technical reform) is 200,000 kilowatts.

(4) New thermal power project (second batch):

The second phase of Qinbei Power Plant is 2×300,000 kilowatts.

Nayong Plant No. 4×300,000 kilowatts.

Jixi Power Plant 4 × 300,000 kilowatts.

Duck Creek Power Plant 4×300,000 kilowatts.

Xiangshui Power Plant 4×600,000 kilowatts.

According to the above-mentioned construction schedule, 7.7 million kilowatts will be put into operation during the 10th Five-Year Plan period, and the installed capacity will reach 13 million kilowatts. After deducting Guizhou Province, it is required to install 7.8 million kilowatts and 400,000 kilowatts of small thermal power units to be retired, with an installed capacity of 4 million kilowatts or more. Guangdong transmission.

3. Yunnan Power Transmission Guangdong (1.6 million kilowatts) Power Project (1) Project under construction:

The Xuanwei Phase 5 was 2×300,000 kilowatts, and the Dachaoshan Hydropower Station was 6×22 million kilowatts.

(2) New Project:

Kaiyuan Power Plant 2×300,000 kilowatts.

The second phase of Qujing is 2×300,000 kilowatts.

Xuanwei Six (2×300,000 kilowatts) and Jidong New Plant (2×300,000 kilowatts) were selected for optimization.

4. Three Gorges Hydropower Station Guangdong Guangdong 3 million kilowatts 5. Hunan Liyu River Expansion 2×300MW Thermal Power Generation Unit 2.2 Power Grid Project 1. Based on the Tianguang-Guangzhou DC transmission channel that has been in operation for two days of 500kV AC transmission and will be put into operation next year, Construction of Tianguang Third Exchange Project: The starting point is the Tianshengqiao Hydropower Station, after the Guangxi Baise Switching Station, Nanning, Yulin Substation to Maoming, Guangdong, the new 500kV AC line is 789 kilometers, and the new Nanning Substation (750000 kV) An) and Baise switch station, supporting the construction of Apple to Nanning 500kV line 112 kilometers.

2. In line with the construction of Tianguang's third return transmission channel, the newly built Tianshengqiao-Luoping-Baofeng 500kV AC line is 317 kilometers, and Luoping substation (0.75 million kVA).

3. New Guizhou-Guangdong AC Transmission and Transformation Project: Construction of a 500kV line from Heshui (Guiyang South) to Guizhou Anshun, and a double loop of 500kV from Hechi to Liuzhou in Guangxi, and Luodong change from Liuzhou to Hezhou in Guangdong. A single 500kV line will be built and a 500kV line between Huishui (Guiyang South) and Fuquan will be built at the same time, involving a total of approximately 1,600 km. New Guiyang South and Hechi substations (each 750,000 kVA) and Anshun and Hezhou switch stations.

4. Newly constructed Guizhou to Guangdong DC transmission and transformation project: The construction of a DC project starting from Anshun area to Guangdong will be considered with a scale of 3 million kilowatts. The length of the line is about 1,000 kilometers, and the transmission capacity is 3 million kilowatts.

After the completion of the above-mentioned power grid project, Guangdong Province has a power transmission network capacity of 1,000 to 10.5 million kilowatts, including: Tianguang DC 1.8 million kilowatts, Guiguang DC 200 to 2.5 million kilowatts, and West Power four times 500 kV AC power capacity 320 Million kilowatts, the Three Gorges power transmission 3 million kilowatts.

In addition, in order to ensure the completion of the above major projects and bring them into play, the following tasks shall also be supported: Accelerating the construction and commissioning of Tianguang DC; the construction of power grid projects supporting the construction of Guizhou and Yunnan provinces; and the construction of supporting power grid projects within Huazhong Power Grid; The construction of power grid projects that need to be advanced or adjusted in the Three Gorges Power Transmission Project; the construction of the secondary system project for power transmission to Guangdong, etc.

3 Thermal power plant instrument control system 3.1 Investment scale of thermal power plant instrument control system A thermal power plant of 2×300MW scale, its investment quota is generally about 2.2 billion yuan, the investment amount of the thermal power plant instrument control system is generally 200~300 yuan per kilowatt. For a 2×300MW thermal power plant, the instrument control system has an investment size of 150 million yuan. If the instrument control system is supplied with the main equipment, the total investment scale of the instrument control system is 2 About 100 million yuan.

As the entire “West-to-East Electricity Transmission” project is too large, only statistics on the construction of 10 million kilowatts of thermal power transmission projects to Guangdong during the “10th Five-Year Plan” period will be carried out. The investment scale of the newly-built thermal power plant instrument control system will be about 4.5 billion yuan. In addition to the thermal power projects of the “West-to-East Power Transmission” project, especially the construction of thermal power projects on the North Passage, the total investment in the instrument control system of thermal power plants will be very large.

3.2 Conventional thermal power plant instrumentation control systems Equipment selection and configuration of thermal power plant instrumentation control systems are determined with the specific conditions of each power plant. As far as domestic newly-built power plants are concerned, on the one hand, the changes in the main process systems of coal-fired generating units are not very large. On the other hand, due to the limitation of domestic investment levels, with the exception of a few special power plants, the automation levels of the power plants in the country are basically in the same level. In the past, the basic configuration of the instrument control system of each power plant in the country is roughly the same. The configuration of the main instrument control system can be briefly described as follows.

1. Distributed Control System (DCS)

Distributed Control System (DCS) is currently the main control system of thermal power plants. Generally, each unit is equipped with one set. The DCS scale of the 300MW project is generally around 5000 I/O. It usually includes four functional subsystems: DAS, MCS, SCS, and furnace safety monitoring. System (FSSS).

Data acquisition and processing system (DAS) is the unit's information center, completes the data collection, processing, and performs functions such as CRT display, recording, alarm, history storage, accident recall, ability calculation, and operation guidance.

The analog control system (MCS) completes the coordinated control of the unit and the control of all the automatic control loops, including fuel control systems, feedwater control systems, steam temperature control systems, milling control systems, and condenser control systems.

The sequential control system (SCS) completes the sequential control functions of each functional unit and unit of the unit unit, including air supply system, inducer system, flue gas system, water supply system, condensate system, and circulating water system.

Furnace Safety Monitoring System (FSSS) is the main safety monitoring system for boilers. Its main functions are furnace purge, fuel system leak test, load control, valve management, automatic turbine control, and turbine overspeed protection.

2. Electro-hydraulic fluid control system (DEH)

The DEH is the main system for controlling the turbine. Its main function is the speed control, load control, valve management, turbine automatic control and turbine overspeed protection for the turbine.

3. Small steam electromechanical control system (MEH)

If the power plant feed pump is driven by a small turbine, the power plant also has a small turbine current man control system (MEH). Its main function is to control the speed of small turbines, load control, valve management, automatic control of small turbines and overspeed protection of small turbines.

4. Turbine emergency shutdown system (ETS)

The turbine emergency shutdown system (ETS) is a control system that protects the turbine. Its main function is to monitor certain parameters of the turbine, and when these parameters exceed the operating limits, the steam inlet valve is closed.

5. Steam Turbine Safety Monitoring System (TSI)

Steam Turbine Safety Monitoring System (TSI) is an instrument system that continuously measures turbine rotor bearing and turbine operating parameters. When an abnormal operating parameter occurs, an alarm signal is issued.

6. Small Turbine Emergency Interrupt System (ETS) and Small Steam Turbine Safety Monitoring System (TSI)

The small turbine emergency shutdown system (ETS) and the small turbine body safety monitoring system (TSI) are critical shutdown systems and on-body safety monitoring systems for small turbines, respectively.

7. Continuous Flue Gas Monitoring System (CEMS)

The Continuous Flue Gas Monitoring System (CEMS) is an instrument system for continuous monitoring of smoke pollution emissions. The monitored parameters are mainly SO2, NOx, CO, dust and so on.

8. PLC program control system for auxiliary workshops The auxiliary systems of thermal power plants mainly include coal transportation systems, ash removal and slag removal systems, chemical makeup water systems, condensate polishing systems, wastewater treatment systems, and fuel treatment systems. The above auxiliary systems basically use PLC for program control.

9. Main field instrumentation and control equipment The main field control equipments of thermal power plants are as follows:

(1) Transmitter. At present, the transmitter used in thermal power plants is generally a smart transmitter. Transmitters have a large number of applications in thermal power plants. For a 2×300MW power plant, the number of required transmitters is around 500 units.

(2) The implementing agency. Actuators have electric actuators and pneumatic actuators. They are selected according to different process systems and control requirements. Currently, electric actuators generally use imported products or Sino-foreign joint venture products.

(3) flow measurement instruments. The air flow measuring instrument can choose plug-in type flow meter, steam, water and other flow measurement instruments can select measuring elements such as throttling nozzle. Since there are many types of process media in power plants, other types of flow meters are still needed.

(4) Instrumentation valve. For high temperature and high pressure instrument valves, imported products are currently used.

(5) Switch meter. Thermal power plant switch gauges have pressure switch level switch, flow switch, powder switch and so on. At present, the measuring instruments used in high temperature and high pressure media mostly use imported products.

(6) Analytical instruments. There are many kinds of analytical instruments in power plants, such as silicate analysis instruments, PH meters, hydrogen analyzers, oxygen content in flue gas, and so on.

(7) Distribution boxes, protection boxes, incubators, etc. Power plants require a large number of electric door distribution boxes, instrument protection boxes, insulation boxes and so on. Power plants require a large number of electric door distribution boxes, instrument protection boxes, instrument insulation boxes and junction boxes and other local bin cabinet equipment.

Because the power plant needs to measure many types of media, including sewage, make-up water, condensate, industrial water, circulating water, coal, pulverized coal, ash, slag, oil hydrogen, oxygen, smoke, air, steam, etc., so in addition to the above In addition to the main instruments, there are many sporadic measuring instruments.

4 New Instrument Control Areas in Power Plants The overall automation of China's power plants is relatively high, but the state is a developing country after all. Due to the restriction of the entire investment, conventional power plants generally only consider basic control functions. With the continuous improvement of the level of automation and management, especially with the objective requirements of the separation of plant and network and competitive bidding, the power plant will pay more attention to the development and application of the control system for improving the economic benefits of the overall management. The power plants associated with the “West-to-East Power Transmission” project all have a problem of reducing the on-grid tariffs to improve competitiveness. These power plants will use some new instrument control systems, as described below.

4.1 New Instrument Control System 1. Plant-level monitoring information system The SIS (Supervisory Information System) is a plant-wide management and control system based on the DCS of each unit unit and the auxiliary system PLC. It is an important management and control integration system formed between traditional process control and MIS. The system manages the entire plant's real-time schedule optimally. From a functional point of view, on the one hand, it collects DCS control system data to achieve power plant operation optimization, load dispatching, economic performance analysis, equipment fault diagnosis, equipment status maintenance and equipment life management, etc.; Passed to MIS in the management system of business, archives, personnel, etc. In terms of physical structure, this layer is between DCS and other control systems with high precision, high speed and high reliability, and non-real-time MIS that do not affect safety production. It is not only a transitional level, but also serves as an isolation zone.

The current SIS system is still in its infancy, and its development function is basically limited to real-time data management, economic performance analysis, load dispatching, and local optimization. The total system cost is between 300 and 10 million yuan.

2. Operation of the optimized control system DCS has achieved the basic functions of the unit control, ensuring that all units of the power plant are put into operation and generating power at full load. In actual operation, it is found that there are still many problems in power plants in one place or another, and there are many places where potential improvements can be made. At the same time, with the continuous development of automatic control theory, new control ideas, methods, and theoretical models have emerged. This makes all kinds of operational optimization software continuously developed and applied.

The optimization software currently used in power plants mainly includes: optimizing the unit's coordinated control, optimizing the main steam temperature control, optimizing the combustion control, optimizing the blowing, optimizing the pollution reduction, and optimizing the startup and shutdown of the unit. . The system optimized for the above operation is an optimized control system. The cost of each optimized control system varies according to the scope and scale of its function, and it is a far cry from it. The small system is about 500,000 yuan, and the large system or import system can be as high as 10 million yuan.

3. Equipment management and diagnosis system There are tens of thousands of equipments in the power plant. It is of great significance to conduct management and fault detection and diagnosis for some major equipment. The systems that have begun to be applied in power plants mainly include: furnace leak detection and alarm systems, and steam turbines. Vibration fault management system.

In addition, systems that manage and troubleshoot diagnostics for other equipment are also very much needed by the power plant. As long as the developed system is suitable for power plants and is inexpensive, it can be used on a large scale in power plants. The development of these systems should be limited to about 500,000 yuan, which is a price that users can accept.

4. Security Surveillance CCTV systems With the increase of automation, more and more unattended shuttle buses or unattended areas have become more and more important. Surveillance of these areas or areas has become more and more important. Security monitoring CCTV systems should be implemented. Students have already begun to apply in power plants.

5. Auxiliary Control Networking System The traditional auxiliary workshops are controlled independently. In order to reduce people's efficiency, the current power plant design has centralized monitoring of a number of workshops in a centralized manner. This has led to the need for auxiliary control networking products. The auxiliary control networking system is a major new system for power plants in the near future.

6. Expert Analysis System The expert system for on-line analysis of certain important media is the product required by the power plant, such as the system for monitoring and analysis of coal entering the furnace, the system for analyzing the water quality of the feed water, the system for analyzing the flue gas, etc. .

7. New instrumentation equipment adopts new measurement principles to simplify instrumentation, use new measurement methods to improve accuracy, and adopt information technology to improve instrument intelligence. These are the development directions of instruments. These instruments are all products that power plants need.

4.2 Instrument control system for desulphurization equipment In order to improve the environmental performance, desulphurization of the flue gas exceeding the power plant is an important part of the future power plant construction. Most of Yungui’s power plants are located in remote mountainous areas, and this issue has not yet been considered. However, if power plants such as Anshun and Guizhou are close to the city or in urban areas, desulfurization systems must be considered. At present, the domestic power plant flue gas desulfurization projects that have been put into operation include: Chongqing Power Plant, Handan Power Plant, Beijing Yire, Zhejiang Banshan Power Plant, etc. These power plants are all desulfurization process technologies introduced from Germany STEINMILLER and Japan MITSUBISHI. Flue gas desulfurization (FGD) currently has wet desulfurization, dry desulfurization, semi-dry desulfurization, etc. Commonly used is the limestone-gypsum wet desulfurization process system, and this desulfurization efficiency can reach 95%. Recently, the domestic power plant flue gas desulphurization project is gradually moving towards the adoption of foreign core technologies, domestically considered equipment and materials are considered for import, and other general equipment and materials can be purchased domestically.

The following is a brief introduction to the control system, primary detection elements, and instruments required for full flue gas desulphurization for a 2×300MW project.

The total investment for this desulfurization project is 150 million yuan, of which the instrument control system has an investment of about 12 million yuan.

The control of flue gas desulphurization adopts the on-site workshop centralized control method, and two sets of desulfurization systems are monitored centrally. Two operator stations are generally set up in the control room. The desulfurization main control system adopts an independent distributed control system, and its basic functions are divided into DAS, MCS, and SCS. The number of I/O points per DCS is around 2200 points. For those common systems such as: limestone preparation, gypsum dewatering, wastewater treatment, air pressure stations, etc. DCS remote stations can be considered. DAS, SCS are basically regular monitoring. The main control loops of MCS are: pressure control of booster fan, limestone slurry preparation control, limestone slurry feed control, absorption tower liquid level automatic control, limestone slurry pool liquid level automatic control, flue gas temperature control, oxidation fan control, etc. .

The medium of the desulfurization system is generally limestone slurry, so its valves are all imported ceramic core valves. The detection instruments for the desulfurization system also differ from conventional system instruments such as smoke and soda in thermal power plants. Considering the particularity of the measured medium, most of the instruments are made of stainless steel. The main instrument is as follows:

(1) Flue gas flow measurement. Desulfurization flue gas flow measuring device for measuring the flue gas volume to calculate the desulfurization efficiency.

(2) Analytical instruments (SO2, O2) for the inlet of the flue gas at the desulfurization island. Balanced or heated analytical instruments.

(3) Analytical instruments (SO2, O2, NOX, CO) for the flue gas outlets of desulfurization islands. Analytical instruments with dilution or heating.

(4) PH analyzer. It is used to measure the pH of absorption tower. PH range is 0~8. 316 stainless steel.

(5) Level gauge. It is used to measure the liquid level of absorption tower, limestone slurry, etc. The meter is equipped with back flushing device.

(6) Thermal resistance measurement of PT100. 316 stainless steel material, temperature range 0 ~ 350 °C.

(7) Electromagnetic flowmeter. It is used to measure the flow of gypsum slurry, limestone slurry, etc. The shell material is 316 stainless steel.

(8) FGD exit dust concentration analyzer. Light attenuation type, using 316 stainless steel, dust content 0 ~ 50mg/m3N.