In the thermal power plants and substations of power systems, DC systems are very important. The reliability and quality of the DC system power supply directly affect the safe operation of the power system. Selection of types of DC power supply is specified in Section 3.2.1 of the "Technical Regulations for DC System Design of Thermal Power Plants and Substations", and fixed-type acid-proof lead-acid batteries are recommended for thermal power plants and substations; At the same time, medium-rate nickel-cadmium batteries can also be used. In Chapter 4 of Chapter 11 of the “Technical Specification for Design of Thermal Power Plantsâ€, there are corresponding provisions for the configuration of this type of battery. For several decades, fixed-type acid-proof lead-acid batteries have been continuously improved. The more mature manufacturing technology and serialized products, the operating unit also has a wealth of experience in the use and maintenance, but there are still many shortcomings in practical applications. For example, the battery has a large volume and occupies a large battery room; acid mist escapes during operation and pollutes the environment; the battery must be installed in places where special requirements are required; ventilation equipment and acid-addition equipment must be installed; special operation is required. Maintenance personnel perform complex and cumbersome routine maintenance. The nickel-cadmium storage batteries have been slow to raise the level of manufacturing technology, and problems such as alkali-leaching and leakage have not been effectively solved, and they still need to be changed periodically. These problems directly affect the stable and reliable operation of DC power supplies, and their product prices are greatly increased. In ordinary lead-acid batteries, it has not been widely adopted in thermal power plants.
VRLA Valves (Regulated Lead Acid Batteries), also known as cathodic absorption lead-acid batteries, are advanced lead-acid batteries developed in the last decade or so. Because it can maintain valve-controlled sealing during use, it does not need to add acid to add water to maintain, no acid mist escapes, does not pollute the environment, and does not corrode equipment. The battery can be placed, placed horizontally or by building blocks, saving floor space. . Therefore, when the VRLA battery appeared, it was widely recognized both at home and abroad, and it was gradually applied. Especially in the field of industrial batteries. According to statistics from foreign sources, about 80% of the fixed and floating batteries in the United States and Europe are valve-regulated batteries. At present, it has been widely used in China's fields such as post and telecommunications, communications, high-rise buildings, and exchanges of uninterrupted power supply.
With the widespread application of VRLA batteries in other areas of China, especially in post and telecommunications, and the rise of VRLA battery manufacturing in China, China's power system has been using VRLA batteries in thermal power plants and substations since the early 1990s. Control protection and power in the DC system. In the newly-built and expanded various types of power transmission and transformation projects and power plants and substations that have been put into operation, VRLA batteries have been used differently throughout the country. In order to standardize design, selection, installation and maintenance of the storage battery in the power transmission and transformation project and the modeling of the supporting equipment of the DC system, it is necessary to understand the practical application of the VRLA battery in the power plant and the substation as the power control power supply in order to formulate corresponding Procedure specification. To this end, we investigated the conditions of selecting VRLA batteries for new construction in recent years in fourteen power design institutes in Northeast China, North China, East China, Northwest China, Southwest China, South China, Hunan, Shanxi, and Heilongjiang; and also applied to some VRLA batteries. Thermal power plants, substations, power supply bureaus and power bureaus investigated to understand the actual operation of VRLA batteries and feedback from users; at the same time, they collected funds from some VRLA battery manufacturers to understand the production process technology, quality assurance and after-sales services of the products. Service measures and improvement and improvement.
Application of Valve Controlled Sealed Lead Acid Battery in Power Engineering
1 Application range
Among the fifteen power design institutes that we surveyed, each of the hospitals selected VRLA batteries in part in the design of the project, plus the operating units replaced the selected batteries on their own. From the small and medium-sized thermal power plants to the large 600 MW capacity The thermal power plant has units that use VRLA batteries to operate from a 110kV unattended mini-distribution system to a 500-kV hub. The battery is used for 48V control, 110V ~ 220V control, and 220V power load, capacity from 100Ah to 4500Ah. The battery installation point is the main control building, network control building or unit control building. The installation method is mostly a steel frame combined structure, and individual small-capacity storage batteries are also installed in the screen and are arranged in the relay room. The earliest commissioned thermal power plant was from 1991 to 1992, and it has been seven to eight years since then. Large-scale adoption started in 1995.
According to the incomplete investigation and statistics of the above design institutes, there are about 30 thermal power plant projects in recent years, and 40 to 50 substation projects have selected VRLA batteries, most of which have been put into operation. It accounts for about 10% of new thermal power plant projects in recent years, and substation projects can reach about 20%, especially in Guangdong, Hunan, Henan, etc. The proportion of projects using VRLA batteries is higher, and substations can reach 50% or so. In the northwest and southwest regions where VRLA batteries are used less often, some of the power plants under construction have also adopted VRLA batteries. In the case of recent tenders for internationally tendered thermal power plants, bidders abroad also bid on VRLA batteries. In addition, some thermal power plants put into operation in the 1970s and 1980s, when the original battery scrap needs to be replaced, there is also a considerable number of power plants replaced with VRLA batteries, making the proportion of thermal power plants using VRLA batteries increase year by year.
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2 Selected battery models
According to the investigation, the types of VRLA batteries used in thermal power plants and substation power control DC power sources are: American GNB, American c&D, British Hawke, Japanese Yuasa, German Sunshine and other foreign companies. General foreign VRLA battery products have good performance, long life, and stable quality. There are also fewer problems. However, due to its high price, which is about 1.2 to 2 times that of domestic-made storage batteries of the same type, only 10 to 15% of users choose foreign products, and most users choose domestically produced VRLA batteries. The main models used are the GFM and GM models of Huada Power Company, accounting for about 50% of the statistics of power plant projects, and the GM model of Shandong Qufu Shengyang Battery Company and other battery plant products.
3 Application in Thermal Power Plants
According to the survey statistics, in the thermal power plants and transformer substations where VRLA batteries are operating, the usage is well over 90%. The other 10% of users are mostly problems of leakage of individual batteries, poor battery uniformity, and especially battery problems that were used before 1995. In addition, there are some cases where the initial capacity of the battery has not reached the rated value, and there are cases where the operating life of the VRLA battery of a very few users has not reached the expected value. The following are the practical applications of two large thermal power plant VRLA batteries.
One is the SMW thermal power plant, with an installed capacity of 4 X 300MW. The control and power flow of the main plant are all using the GMD (GM) type VRLA battery of Huada Power Supply Company. The capacity is 500 amps (110V) and 1500 to 1870 ampere-hours (280V). There is no end-battery. It is installed in the battery room of the unit control building, with a five-story steel structure. Axial flow ventilators are installed indoors and the room temperature can reach above 35°C in summer. The network control room has no battery and is powered by the main plant DC system. There is no special battery maintenance team for the power plant, which is managed by relay protection classes. There are only 7 people in the protection class. It is necessary to manage the relay protection, control, automatic device, and DC system of the entire plant with 4 units and the network control room. The manpower is very tight. It is impossible to invest too much labor in battery maintenance. The battery is normally operated in a floating charge state. The KGCA40 silicon rectifying charging device of the green factory is supported. The float voltage is generally 2.23 volts, and the float charge current is small. Since the first battery was put into operation in 1992, no uniform charging or regular large-scale discharge has been carried out. Maintenance personnel conduct inspections and regularly clean dust. Measure battery voltage and other minor maintenance work. In the initial stage of operation, the leakage of the individual battery poles has been replaced in time, and the whole plant battery has been operating normally.
Huada Power Company intends to conduct a capacity test with the plant to understand the actual capacity of the battery after 6 years of operation.
The YJZ thermal power plant, which is close to the time when VRLA batteries are put into operation by SMW thermal power plants, has an installed capacity of 6×200 MW. The units have been put into production since the 1970s. In 1992, one of the unit's fixed-type anti-acid batteries was replaced with a domestic-made VRLA battery. The capacity was 1000 amps, and there were no end batteries, a total of 130 batteries. The battery room installed in the central control room of 6.2 meters was close to the boiler room, and the environment was poor. At the time of charging, the recorded summer room temperature was as high as 40.5 degrees Celsius. The battery is normally operating in the floating charge state, and the original KGCFA type charging device is not replaced. Its performance is poor, and the stability of the voltage stabilization current is not high, and the float charge current to the battery sometimes reaches about 2A. The operation and maintenance personnel of the power plant are maintained according to the original battery regulations. When the unit is sized and repaired, large-scale charging and large-discharging are performed. The constant current timing charging method is used, and sometimes the voltage of a single bottle can reach 2.9V or more. When used until about five years, the battery capacity was found to be insufficient in a charge and discharge process, and the individual battery voltage was low. When the battery was recharged and discharged, multiple batteries were damaged and the battery pack was scrapped.
4 Comments and Suggestions from the Operating Unit
Summarizing the operation of VRLA batteries and the opinions and suggestions of power plants and power supply bureaus, VRLA batteries have considerable advantages in engineering applications. First, the VRLA battery is small in size, and the steel frame assembly is installed, which not only saves space, reduces the total building area of ​​the main plant, and is simple and convenient to install. In addition, the maintenance-free features of the operating unit are very popular. In the new thermal power plant project, most of them have adopted the new plant's new staffing standards. In order to achieve higher economic efficiency, no special DC equipment operation and maintenance personnel are generally set up. In the case of VRLA batteries that have been used in thermal power plants that have already been operated, there are generally no special maintenance personnel. For old factories that have already been built, the purpose of reducing people’s effectiveness can also be achieved. In addition, the battery runs without acid mist, which is also in line with the requirements for the construction of a modern pollution-free thermal power plant. Therefore, although there are some problems in the early use of VRLA batteries, users still take a very positive attitude. At the SMW power plant, technical personnel of the maintenance personnel and production management departments of the class were very welcome to use VRLA batteries and believed that they actually reduced their maintenance workload. Some old plants that replaced VRLA batteries, although they still have specially maintained shifts, think that the workload has been greatly reduced to less than 1/3 of the original. In addition, in the SZ Municipal Power Supply Bureau, there are eleven people in the power substation of the Substation, managing 50 A number of substations, originally using GAM type lead-acid batteries, have a considerable amount of work and are equipped with several automotive running maintenance. Recently, it has been gradually replaced with VRLA battery, especially supporting the use of intelligent high-frequency switching power supply as a battery charging device. The battery float charging performance is good, and remote monitoring of the battery can be realized, and the maintenance work is greatly reduced. At present, more than a dozen stations have been replaced, and all of them are being gradually replaced by VRLA batteries and intelligent charging equipment to achieve remote monitoring.
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Problems to be noted when using valve-regulated sealed lead-acid batteries
Although there are many advantages of VRLA batteries, but one thing can not be ignored, that is, its price is higher than the fixed type acid-proof lead-acid batteries, about the latter's 1.5 to 2.5 times, taking into account the land and bag-free equipment The cost of its comprehensive construction is still higher than the latter. People have paid a higher price, and they hope to make full use of VRLA batteries with less maintenance and longer service life. How can we better use VRLA batteries? We believe the following aspects are crucial.
1 Requirements for battery performance and quality
Firstly, the performance and quality of the battery itself must be good. The development of the VRLA battery has been started. The foreign sealed battery technology started in the 1970s. In the 1980s, production of batch and high-capacity VRLA batteries began. The main products are German sunshine. Gel Cathode Absorption Cells, Hybrid Grating Cathode Absorption Cells of the United States GNB, and Japan's Yuasa Inc.'s Cathode Absorption Pole Plate Cells. Early in the storage battery of each company, due to design and production process reasons, there were also problems such as non-uniform capacity, leakage, heat and water loss of the battery, and early failure, which made the reliability of the battery lower and the actual life expectancy lower than expected. According to statistics from foreign sources in the late 1980s and early 1990s, the failure rate of VRLA batteries was as high as 3.2% to 5%. In the 1990s, the production technology of foreign VRLA batteries has matured to solve key problems such as corrosion of plate materials, leakage of safety valves, welding and leakage of poles, and reduction of self-discharge rate, so that product quality has been significantly improved. Occupy the battery market. Such as the United States c & D's VRLA battery, with a special shell, cover and polar sealing technology, the use of a unique mother grid technology and a single plate slot formation, oxygen composite rate as high as 99.9%, making the pressure relief valve is as low as o .067kg/cm2, in addition, the corrugated shell is designed to facilitate heat dissipation, and the steel frame combination is solid and convenient. Therefore, the life expectancy of c&D 2000 series floaters can reach 20 years.
The same goes for the production of domestic VRLA batteries. In the 1980s, Huada Power Company introduced the GNB technology to produce GM-type batteries. There have also been problems such as battery leakage. Based on this, in 1995, Huada Power Co., Ltd. introduced an improved GFM-type battery, which mainly improved the plate material. , thickness and assembly process; the manual pole welding was replaced by computer-controlled argon arc welding; epoxy resin double seal was applied at the pole. The safety valve adopts double-layered sulfuric acid explosion-proof structure and so on. There are more than ten improvement measures, which greatly improve the performance and quality of the GFM type battery.
Although the production technology of VRLA batteries is becoming more and more perfect, the quality of its products varies from manufacturer to manufacturer. In 1995, there were more than 50 VRLA battery manufacturers in China. The rapid development in recent years has reached hundreds. Some of the VRLA battery manufacturers use imported foreign technologies or production lines, have a certain scale of production, have strong technical force, advanced equipment, stable product quality, and good after-sales service, such as the GFM type battery of Huada Power Company, introducing the US GNB production technology and production line. equipment. Shandong Qufu Shengyang Battery Co., Ltd. began production of VRLA batteries in the 1980s. In the 1990s, it introduced advanced production technologies and equipment from the United States and other countries. Hangzhou Nandu Power Supply Company GFM type batteries use Tudor Group Dental Dental and Hagen's patented technology. , The introduction of production equipment from countries such as the United States, which has been widely used in post and telecommunications, communications and other fields. All these factories have passed ISO9000 quality system certification.
There are also some storage battery factories with weak technical strength, small scale, backward equipment, semi-manual production, no series production, lack of necessary quality supervision, no relevant tests or incomplete tests, inaccurate characteristic curves such as discharge curves, etc. Wait. The quality of these plants cannot be guaranteed, but they also occupy a part of the market at low prices, and some problems have also emerged. However, the short-term behavior of short-term operations and poor product quality are not yet very clear.
As VRLA eight battery market has a variety of products, the choice of plant in use is very important, some users blindly believe that some manufacturers do not understand the investigation, in-depth understanding of the investigation, only the low price as the only option This will have very harmful consequences. According to the product performance, performance, quality assurance system and after-sales service measures, under the same technical conditions, comprehensive consideration of the cost-performance ratio to filter different models of different manufacturers.
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2 Correct design, installation and selection
In addition to requiring VRLA batteries to be of good quality and robust, it is also important to properly design, install, and maintain VRLA batteries. First of all, the design choice calculation of VRLA battery has its special requirements. The previous regulations and design manuals are for fixed anti-acid lead-acid batteries. For VRLA not fully applicable, VRLA battery float voltage is slightly higher than ordinary lead. Acid batteries, different characteristics, the number of choices are also different, different types of batteries should be calculated with different parameters. The Department of Power Engineering's new DC screen design and development team wrote the "GWM (GM) VRLA Battery Power Engineering Design and Installation Application Manual" for the Huada GFM batteries in 1993 and 1996, which has played a role in the design of VRLA batteries. Positive guidance. In addition, the “DC System Design Software†compiled by the Henan Electric Power Design Institute also enters the discharge curves of different models of VRLA batteries from different manufacturers into the software database, and can calculate the battery selection according to different models. In this way, the design of the VRLA battery can be guaranteed to be correct, reasonable and effective. Recently, the “Power Engineering DC System Design Manual†published by China Power Industry Press has also discussed VRLA batteries in more detail.
Second, VRLA batteries are very sensitive to temperature. For every 10°C increase in battery temperature, the battery life is halved and the manufacturer's service life is a value at 25°C. When the temperature rises, the self-discharge of the battery increases and the loss of water accelerates, which can lead to early failure of the battery due to water loss. In addition, the float charge voltage of the battery is closely related to the temperature. In general, the floating voltage should be reduced by about 0.33-o.04V per 1°C. Therefore, the ambient temperature of the VRLA battery should be controlled at 5 °C ~ 30 °C as well, and the float voltage of the battery is adjusted according to different temperatures to ensure its service life.
3 Special requirements for charging devices
In addition, the performance of charging equipment configured with DC systems also affects the service life of VRLA batteries. In the "Technical Regulations for the Design of DC Systems for Thermal Power Plants and Substations", it is required that the steady-state accuracy of the charging device should not exceed 5%; the accuracy of the voltage regulator should not exceed 2% of the soil; and the ripple factor should not exceed 2%. This is common lead. Acid batteries are sufficient, while VRLA batteries have higher requirements. VRLA battery float voltage is generally 2.23 ~ 2.25 volts, a stable floating voltage helps the battery characteristics of stability, and in the temperature changes, the floating voltage should be followed with minimal adjustment, such as the accuracy is not high, you can not adjust In addition, the charging device outputs the ripple component of the DC power supply, which will cause irreversible damage to the VRLA battery. Therefore, it is necessary to configure a charging device with high stability of voltage and current stability, especially with a small ripple factor. It is better to select a charging device with battery detection, automatic adjustment, and monitoring alarm functions to achieve unattended maintenance and battery monitoring. . Therefore, smart microcomputer type charging devices and high-frequency switching power supplies are all suitable supporting devices.
4 Pay attention to the operation and maintenance of the battery
The correct operation and maintenance of VRLA batteries is also crucial. Since VRLA batteries have not been used in power plants for a long time and have little experience, operation and maintenance personnel generally feel that the performance characteristics of VRLA batteries are not well understood and there are no rules to follow. It is either misunderstood or maintenance-free. In fact, this only means that there is no need to add acid to add water to the operation, and it is not unmaintainable. Either the operation and maintenance of ordinary lead-acid batteries have been followed for many years, causing damage to VRLA batteries. Some damage to VRLA batteries is related to improper operation and maintenance. For example, the battery group scrapped by the YJz power plant mentioned above was mainly caused by improper charging and discharging. While choosing the VRLA storage battery, should strengthen the training to the related personnel, raises the maintenance movement personnel's quality, carries on the work according to the VRLA storage battery specific operating procedure. In this way, VRLA eight-battery batteries can be truly maintained and reach the expected service life.
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in conclusion
To sum up the above investigation and analysis of the application of VRLA batteries, we believe that the application of valve-regulated sealed lead-acid batteries in thermal power plants has problems such as a slightly higher capital investment, less operating experience, and poor battery quality. With the increasingly widespread application and technology of external VRLA batteries, the above problems will be gradually solved.
The VRLA battery has the advantages of space saving, simple operation and maintenance, long service life, and other advantages that are incomparable to other types of batteries, especially in the current situation where the power industry has reduced staffing and efficiency, and it has a very positive significance. Therefore, VRLA batteries are also welcomed and recognized by power system users and production management departments.
With regard to the problem of slightly higher capital construction costs, such as the expected value of the service life and the cost of the manpower saved by the operation and maintenance, the trace prices are comparable. Therefore, in the firepower
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