Title of Electrical Paper Chapter 1
Low-voltage electrical installation technology in building electricity
Abstract: With the development of China's economy and the acceleration of urbanization, there are more and more residential community construction projects. Low-voltage electrical equipment is the infrastructure in building engineering, which is related to people's daily life, and construction quality management must be done well. Low-voltage electrical installation project generally has a long construction period and complex working procedures, which are affected by many factors and involve cross-construction in the construction process. Therefore, scientific and reasonable arrangements must be made to improve the construction technology, so as to effectively ensure the quality of low-voltage electrical installation.
Keywords: architecture; Low voltage electricity; fixed
In recent years, China's electrification installation technology has been continuously improved, and it has been widely used in construction projects, which has brought great convenience to people's daily life. However, the installation technology of low-voltage electrical equipment is complex and professional, and various cross-constructions are involved in the construction. Therefore, it is of great practical significance to study the installation technology of low-voltage electrical equipment in buildings to promote the development of the construction industry.
1, general situation of low-voltage electrical installation engineering characteristics
Pay attention to prevention and strictly control quality. Because the installation of low-voltage electrical equipment is easily influenced by many external factors, there are many quality hidden dangers in every engineering link. Therefore, it is necessary to strengthen the prevention work and strictly control the construction quality to ensure that the construction progress and installation quality of the project meet the engineering requirements. There are many influencing factors, which are comprehensive and involve a wide range. Low-voltage electrical installation in building engineering has the characteristics of many types of work and long construction period, which determines that the project will inevitably face the characteristics of many influencing factors, strong construction comprehensiveness and wide coverage. The construction period is long and the type of work is complex. Before construction, civil works such as grounding grid and pipeline laying should be done well, and welding work should be carried out; After this process is completed, it will enter the stage of equipment debugging. After the completion of all projects, the electrical system will generally be debugged, and then the final completion acceptance will be carried out by relevant departments. This process involves civil engineering, equipment installation and debugging, engineering quality acceptance and other types of work.
2. Low-voltage electrical installation technology of building engineering
2. 1 Fully understand the design intent of the drawings.
Construction drawings are the premise to ensure the normal development of construction. Only on the basis of full familiarity with construction drawings can we organize effective construction activities, find problems in time and solve them quickly, and promote the smooth development of engineering construction activities. Generally speaking, electrical systems have a variety of equipment and pipeline configurations. Before electrical engineering construction, it is necessary to review the construction drawings, especially the changed parts in the design, and scan them one by one.
2.2 Installation technology of electric cabinets, boxes and distribution boards
The construction technology for the installation of electric cabinets, boxes and switchboards mainly includes the following items: (1) When installing electric cabinets, boxes and switchboards, the construction personnel should not only accurately locate the installation position, but also ensure the correct connection of internal lines, so as to ensure the safe operation of the whole power equipment. (2) When making electrical cabinets, boxes and distribution boards, non-combustible materials should be selected to ensure firm installation and normal technical parameters. (3) The distribution of components in the box shall be determined according to the drawing structure, and the division between each phase sequence shall be carried out strictly, and the line interface shall be operated in strict accordance with the drawing. (4) The metal frame and foundation steel of the electric cabinet, electric box and switchboard shall be properly grounded, and corresponding openable doors shall be set. Bare copper wire should be used to connect the door and the frame grounding terminal, and corresponding electric shock protection should be provided at the same time. Pull-out power distribution cabinet should keep normal operation when pushing and pulling. (5) The lines in the electric cabinet, electric box and switchboard shall be neat and orderly, and the wires shall be closely connected, and there shall be no broken strands or damaged core wires. (6) Set the action current of the leakage protection device reasonably to avoid safety accidents.
2.3 Installation Technology of Embedded Pipe Fittings
As an important part of low-voltage electrical installation in building engineering, the quality of pipe fitting pre-embedding and welding is very important. However, in practice, due to the uneven skills of construction workers, it is easy to be buried by mistake, missing or without installation drawings and construction specifications. Specifically, the construction technology of pipe fitting embedment includes the following aspects: site construction personnel should carefully check the position, quantity, specification and model of embedded parts with drawings, and carefully check the corrosion prevention, nozzle treatment and welding of steel pipes; The connection between pipes, bending flatness, bending radius, junction box and junction box shall comply with relevant regulations; Check the construction quality of equipment foundation, grounding device and grounding grid; Measure the grounding resistance of grounding grid, and increase the number of grounding electrodes or take other remedial measures for the part that does not meet the design requirements.
2.4 Installation Technology of Grounding Device
The distribution of grounding devices should be carried out according to the construction drawings of low-voltage electricity consumption in building engineering, and the grounding resistance value should meet the standard design requirements. When laying a trunk line with lightning protection and grounding, the buried depth of the pedestrian passage should be greater than 1m, and asphalt should be laid above the pipeline. The buried depth of the top surface of the grounding module should be greater than 0.6m, the spacing between grounding modules should be greater than 3 ~ 5 times of the module length, and the buried foundation pit is generally 1.2 ~ 1.4 times of the overall dimension of the module, and all indicators should be recorded in the excavation depth. The grounding module should be kept in a horizontal or vertical position, and at the same time, the contact distance between the upper floors should be well grasped. The leads of the grounding module should be centralized, and the grounding module should be welded in parallel with the trunk line to form a loop, and the material of the trunk line should be consistent with the welding points of the grounding module. During dark application, fix the down lead in the plastering layer. When used naked, the down conductor should not be bent and should be as flat as possible. Paint should be used to prevent corrosion at the welding position of the bracket.
2.5 Installation Technology of Wire Tube and Trough Laying
The key points of laying wire tubes and trunking include: metal wire tubes and trunking must be reliably grounded or connected to zero. Steel conduit and metal trunking cannot be welded with jumper grounding wire, and the jumper grounding wire needs to be fixed at the joint with special grounding card, and the cross section of copper core cord between the two cards is greater than 4mm2. When the nonmetallic conduit is connected by thread, both ends of the joint are connected by ground wire. Explosion-proof conduit can't be connected by inverted buckle, and metal conduit can't be connected by butt welding. When the insulated conductor is buried on the masonry, cement mortar with strength grade greater than M 10 shall be used for plastering protection, and the thickness of protective layer shall be greater than15 mm. When laying cable conduit outdoors, the buried depth shall be greater than 0.7m, and the steel conduit with wall thickness less than 2mm shall not be buried in outdoor soil. All nozzles should be sealed after passing through cables and wires. The conduit leading to the building, the conduit opening at one side of the building should be located in the building. The inner and outer walls of metal conduit should be treated with anti-corrosion, and the inner wall of conduit buried in concrete should be treated with anti-corrosion. The distance between the buried depth of the concealed pipe and the surface of the building should exceed15 mm; When the conduits are equipped, they should be arranged neatly, the fixed points should be evenly spaced and installed firmly. Conduits and trunking shall be equipped with compensation devices at the deformation joints of buildings.
2.6 low-voltage electrical installation with the construction technology
As mentioned above, the installation of low-voltage electrical equipment in building engineering involves many processes, and each process often crosses construction. Therefore, before the installation of low-voltage electrical equipment, we should coordinate the construction sequence of each major and correctly weigh the importance of different construction sequences, so as to scientifically arrange the progress of different construction types. For example, when coordinating low-voltage electrical installation with civil engineering and water supply and drainage construction, we should pay attention to the following matters: (1) Low-voltage electrical installation of building engineering will affect the progress of civil engineering, so when coordinating the two, we should grasp the primary and secondary, and realize that civil engineering is the mainstay, and low-voltage electrical installation projects will fully cooperate with civil engineering. (2) When low-voltage electrical installation cooperates with water supply and drainage engineering in building engineering, the drawings of two types of work should be carefully compared and studied first. Because the drawings of these two types of work may be different in different degrees, for example, when the lines and pipes of low-voltage electrical installation conflict with the drainage pipes of water supply and drainage, it is necessary to do a good job in the installation of each pipe and determine the installation sequence before installation.
3. Debugging and operation technology of low-voltage electricity in building engineering.
After the low-voltage electrical installation project of building engineering is completed, it is necessary to check the operation of all components in the low-voltage electrical installation project to ensure the effectiveness of the low-voltage electrical installation. Specifically: (1) The running current and voltage of complete power distribution (control) equipment should be in normal state. (2) Observe whether the steering and mechanical rotation of the motor are normal after electrifying, and the no-load test run time of the motor is 2h. The AC motor is continuously started twice in no-load state, and the disconnection time for both times is more than 5 minutes, and it can only be started again after the motor temperature is normal; During no-load operation, parameters such as current, voltage, temperature and running time should be recorded to ensure that the requirements of electric movable property are met. (3) After the lighting system is electrified, the circuit control of lamps and lanterns should be the same as the distribution box, and the control sequence of switches and lamps and lanterns should also be handled one by one.
4. Conclusion
In short, the quality of low-voltage electrical installation in construction projects directly affects the overall quality of the project, so we must attach great importance to its project quality management. It is hoped that more experts and scholars will provide guidance on the basis of this research to effectively improve the quality of low-voltage electrical installation projects.
References:
[1] __ minutes. Construction requirements for building low-voltage electrical devices [J]. Guangdong Building Materials, 2009,25 (7)
[2] Sun Kun. On the Construction of Low-voltage Electrical Devices [J]. Science and Technology and Enterprise, 20 12(3)
[3] Shen. Low-voltage electrical installation quality control measures [J]. Investment and cooperation, 20 1 1(6)
The second part of the topic of electrical paper
Analysis of electrical energy saving in industrial electrical design
With the popularization of a large number of energy-saving transformer products, many design units are still using S7 series transformers. According to many years' working experience, this paper introduces what measures can be taken to achieve the purpose of energy saving and emission reduction from the aspects of power supply and distribution system design, control system design, lighting system design and equipment selection, so as to realize the safety, economy and energy saving of the scheme.
Electrical design; Voltage; Level; Electric energy saving
order
According to the survey, the ratio of GDP growth rate to energy consumption growth rate in China is 1: 1.5, but the standard national economic growth rate and energy consumption growth rate should be: 1: 0.8. Through comparison, it is concluded that China's energy-saving work needs to be improved. Although China has a vast territory and abundant natural resources, the resources are still insufficient. Therefore, in order to achieve sustainable development, we must make effective use of resources, and the most important thing is to make an energy-saving plan, and plan and implement it as planned from the aspects of safety performance and energy saving.
1 Rational design of power supply and distribution system
The main differences between industrial electricity and ordinary civil electricity are: high power load level, relatively dense electrical equipment and high requirements for continuous power supply. In order to achieve the effect of energy saving, consider from the following aspects.
(1) The power supply and distribution system should be simple and reliable as far as possible. Too many power distribution links will cause extra energy loss. This is also the reason why the Code stipulates that "the distribution series of the same voltage level power supply system should not exceed two levels".
(2) The power supply voltage level of the equipment should be reasonably selected. Under the same conditions, the voltage level is high and the loss is relatively small. For example, compressors and circulating pumps, which are widely used in industries and enterprises, often use 6/ 10kV power supply, which not only reduces the current on the power supply line, but also reduces the copper loss and waste of copper materials.
(3) The substation should be as deep as possible into the load center. In most cases, the load in industry and enterprises is mostly low-voltage AC 380V V V. If the distance is too far, increasing the cross section of the cable to meet the requirements of start-up voltage drop and operation voltage drop will inevitably cause a lot of copper waste. Therefore, if the factory area is too large, a reasonable power supply radius should be adopted for unified planning, and multiple power transformation and distribution devices should be set up to shorten the line distance and reduce the loss. If there is an explosion danger zone, on the premise of meeting the specifications, the substation can be set outside the explosion danger zone, and the height difference between indoor and outdoor floors can be increased to 0.6m to achieve the effect of reducing energy consumption.
(4) Power factor compensation is adopted. In industrial enterprises, most electric loads are pumps. After SH3038―2000 "Technical Specification for Power Design of Production Units in Petrochemical Enterprises" was issued, the designers of petrochemical units cancelled the low-voltage compensation, which was inappropriate. If compensation is only set on the 6/ 10kV side without compensation on the low-voltage side, the number of distribution transformers will increase or the transformer capacity will increase correspondingly when the load is high, which will easily lead to extra power waste. Therefore, the principle of local compensation should be adopted in the design to ensure energy saving, that is, the back of the transformer should be compensated accordingly, so as to improve the efficiency of the transformer under the same load rate.
Reasonable selection of transformer: Transformer is one of the most used devices by designers, but it is often one of the most unreasonable devices. There are two situations:
(1) At present, a large number of energy-saving transformer products have been introduced, and many design units are still using S7 series transformers. Many power departments often tear down old transformers in big cities and move them to urban-rural fringe or rural areas, which not only causes a lot of power loss, but also increases the extra expenses of low-income people. Therefore, designers should strictly control the design, and put an end to the repeated use of national eliminated products and backward products transformers from the source. Try to choose energy-saving transformers with low loss, such as S9, S 10, S 1 1, SC9, SC 10, etc. Energy-saving transformer greatly improves the manufacturing process of silicon steel sheet and iron core, which is beneficial to reduce the no-load power loss of transformer.
(2) The capacity and quantity of transformers are also related to energy saving. Due to the high demand for electricity (mostly primary and secondary loads), industrial enterprises always follow the idea of being fully prepared for each other (that is, the load rate of a single transformer is less than 50%, and two transformers bear the power load). The primary and secondary loads can be completely standby for each other, and for the tertiary load, a transformer can be completely set up, so that the load rate of the transformer can be increased to about 75%. Although the number of transformers has increased, the total capacity of transformers has decreased, and some reactive power losses and active power losses have also decreased. Of course, increasing the number of transformers will also cause losses and increase the building area. All factors should be considered comprehensively to achieve the best results.
2. Reasonable design of control system
In industrial enterprises, in order to improve the degree of system automation and reduce labor costs, the logic control of distributed control system or programmable logic controller is often involved in production devices and production lines. In the previous design, in order to reduce the primary production cost and the number of DCS points, the start and stop to be controlled were controlled by a relay output. If 1 relay contact is used for control, the capacity of uninterruptible power supply (UPS) used in DCS is usually larger than that when two relays are used for control. Even if the output I/O card is added, good energy-saving effect can be achieved.
The advantages of using two relays are: if the equipment is started for the first time on site, the equipment running during the rotation of the transfer switch will not stop after it is started successfully; When 1 relay is selected to control the start and stop of the equipment, the equipment running during the rotation of the transfer switch will stop.
3 Reasonable design of lighting system
The design of electric lighting in industry and enterprises is not as complicated as that in civil buildings, but a large number of lamps are used in the devices at the same time.
(1) The commonly used lamps in the past include mercury lamp, sodium lamp and metal halide lamp. These lamps are widely used in industrial and mining enterprises and have played their due role. However, after the introduction of the new light source, it gradually lost its original dominant position, and its shortcomings such as low light efficiency, short service life, low power factor and long start-up time could not meet the lighting requirements of modern petrochemical enterprises. Therefore, electromagnetic induction lamp, LED lamps and other light sources are introduced, which can completely meet the requirements of users, as shown in Table 1. Although the price is slightly higher, with the promotion, the cost will gradually decrease.
Table 1 Comparison table of various light source parameters
Note: refer to the manual of common electrical equipment in the factory and the manufacturer's samples.
(2) In the past, the control of light sources could not achieve the effect of energy saving. If appropriate measures are taken, such as light control, time control and output adjustment, a lot of electricity can be saved every year.
(3) The new lighting design standard increases the energy-saving part and limits the power density of the main functional buildings. For example, in article 6. 1.2 ~ 6. 1.7 of GB500342004 "Design Standard for Building Lighting", the related item "When the illuminance value is higher or lower than the specified table, the lighting power density should be increased or decreased in proportion" fully reflects the requirements of our country.
4 scientific selection of equipment
Machine mercury is the main power load of industry and enterprises. Although electrical professionals are not responsible for choosing organic mercury, they can still give more scientific suggestions in the design preparation stage. If the power of the selected motor is high, the safety during operation can be improved. However, under light load and no load, it often leads to low work efficiency. Therefore, it is possible to install variable frequency governor for this kind of motor, which can not only improve work efficiency, but also save more energy.
5 abstract
In a word, electrical designers should try their best to complete the design work, study from the aspects of safety performance, energy saving and economy, and finally select a scientific power supply and distribution scheme, further improve the scheme and put it into practice, so as to contribute to improving social and economic benefits.
References:
[1] Wang Zhaoan, Liu Jinjun. Power electronics technology (5th edition) [M]. Beijing: Machinery Industry Press, 20 1 1.6.
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