Lighting system is the core system in building electricity, and it is also a big power consumer. The power consumption of electric lighting system is affected by many factors, including the total time of electric lighting equipment; Loss of complete electric lighting equipment. In addition, the energy loss of electric lighting equipment in the process of converting electric energy into visible light is also affected by the luminous efficiency of lighting equipment.
1. 1 Determine a safe and reasonable lighting scheme for the electrical system.
First of all, we should choose a reasonable lighting scheme on the premise of ensuring safety and reliability. In the design of artistic lighting, the design should be carried out according to the principles of economy, applicability and practicality, and the economy and reliability of the whole lighting system should not be reduced in order to pursue artistic forms unilaterally. In the lighting design of intelligent high-rise buildings, areas with air conditioning can choose the combined energy-saving system of lighting and air conditioning. When designing lighting for occasions requiring high illumination or improving light color, two or more light sources should be selected according to the actual situation of the site to form a perfect mixed light lighting system. See table 1 for four commonly used mixed light matching characteristic parameters of building electrical lighting system. Secondly, the illumination standard of the lighting system needs to be selected. When designing the lighting system, it should be designed according to the technical requirements in GB50034-2004 Standard for Lighting Design of Buildings.
1.2 Choose a safe, economical and efficient light source.
The choice of light source is an important part of the lighting system selection design of the whole high-rise building. When selecting the light source type of lamps, we should combine the actual engineering situation, the visual requirements of personnel for lighting, the use place of lamps and the requirements for lighting quality and quantity, and take high luminous efficiency, safe operation, long service life and high cost performance as the criteria for selecting light sources on the premise of meeting some basic technical requirements such as color rendering and start-up time of lighting areas.
1.3 Select efficient energy-saving lamps.
When designing the electric lighting system of high-rise buildings, all kinds of light sources are rarely used separately, but they are usually used complementarily according to their advantages and disadvantages, so as to reflect the practical application value of all kinds of light sources and achieve the effect of energy saving and consumption reduction. Improper collocation of lamps and lanterns, low efficiency of lamps and lanterns. , which may make the lighting system waste up to 35% ~ 45% of electric energy resources. Therefore, lamps with high energy conversion efficiency and good light control effect need to be selected in the design.
2 safety and energy-saving design of motor
Because the motors in the electrical system of high-rise buildings are generally matched with professional equipment such as HVAC, water supply and drainage, wire system, construction, etc., which are uniformly provided by equipment manufacturers. Therefore, its energy-saving measures should be implemented in the operation process in combination with the safety situation of the actual project. In the equipment system, the line active loss caused by the transmission of advanced reactive power can generally be reduced by local compensation capacitors. At the same time, we should try to reduce the light load and no-load of the motor, because in this case, the efficiency of the motor is very low, and the consumed electric energy will not change linearly with the decrease of the load.
3 transformer safety and energy-saving design
In the safe and energy-saving design of transformer, the key is to reduce the active loss of transformer. Transformer active power loss δPb can be expressed as: δPb = Po+PKβ2(kW), where: Po- transformer no-load loss (kW); Pk—— On-load loss of transformer (kW); β-load rate of transformer. (1)Po, also known as iron loss, consists of eddy current loss and leakage loss of iron core, and its size is determined by the performance of silicon steel sheet and the manufacturing process of iron core, which is generally fixed for a certain type of transformer produced by a factory. Therefore, transformers should be safe and energy-saving, such as oil-immersed transformers or dry-type transformers of S9, SL9 and SC8. By using high-quality cold-rolled oriented silicon steel sheets, they reduced the eddy current loss of the iron core; The 45 inclined joint structure reduces the magnetic leakage.
(2)Pk is the line loss of the transformer, which is related to the resistance of the transformer winding and the current flowing through the winding, and is proportional to the square of the load factor β. Therefore, when choosing a transformer, choose a transformer with smaller winding resistance, such as a copper core transformer. Generally speaking, when β=50%, the energy consumption per kilowatt load of transformer is minimum. However, in actual operation, it is uneconomical to take the load rate of transformer as 50%, and it is economical and safe to take the load rate of transformer as 75% ~ 85%, so that proper capacity can be reserved when the transformer is used. (3) When the building has a large capacity and needs to select multiple transformers, the number of transformers should be reduced as much as possible and more transformers with large capacity should be selected. For example, when the required installed capacity is 4000kVA, two 2000kVA transformers can be selected instead of four 1000kVA transformers, which can achieve better energy-saving effect.
4 power supply and distribution line loss control
Power supply and distribution lines are the direct carriers of power transmission in the whole high-rise building, and their trunk lines, branch lines and other lines form a crisscross and intricate network with a total length of tens of thousands or even hundreds of thousands of meters, so the power consumption on the lines is very large. How to control the loss of power supply and distribution lines is also a key point in the energy-saving research of electrical systems in high-rise buildings. General power supply and distribution lines will produce power loss when current passes through, and its calculation formula is: Δ p = 3i2r×10-3, where Δ p refers to the power loss (kW) of three-phase transmission lines; Single line current (a); R-line phase resistance (ω). As can be seen from the above formula, to reduce power loss, it is necessary to reduce current and resistance. Usually, the current has specific requirements, so to reduce the loss, we must start with reducing the resistance. Reducing line resistance should be considered from the following aspects.
(1) Reasonable selection of distribution voltage level of high-rise buildings. At present, there are more and more high-rise buildings, and the power supply radius of low-voltage power supply should not exceed 150m. For buildings whose height exceeds 150 m, distribution transformers should be placed at the appropriate height level of the building to improve the power supply voltage level, shorten the power supply radius and reduce the loss of low-voltage distribution lines. For example, Nanjing Zifeng Building, which has been completed at present, has a total building height of 450 m, and some distribution transformers have been installed on the 89th, 35th and 60th floors respectively. The Oriental Gate, which is under construction in Suzhou Industrial Park, has a building height of 278m, and some distribution transformers were also placed on different floors of the building during the design.
(2) Reasonable selection of conductor type. In practical engineering applications, new materials with low conductivity are generally selected, among which copper core cable has the best efficiency of transmitting electric energy, but the cost of copper is higher, so the principle of safety, economy and practicality should be followed when selecting conductors. Copper conductor can be selected for Class I and II buildings with heavy load, and aluminum conductor can be selected for Class III or buildings with light load. (3) Reduce the length of low-voltage distribution lines. In order to shorten the safe power supply distance of low-voltage lines and reduce the power loss, substations should be set as close as possible to the load center, and the low-voltage substations of substations should be as close as possible to the high-voltage shafts of buildings. (4) Increase the section of the cable. In the design process of high-rise building electrical system, it is inevitable that some electrical equipment will be far away from the power supply system. When selecting and designing these long-distance lines, the larger cable section should be selected according to the actual situation on the basis of satisfying the basic safety functions such as dynamic thermal stability, voltage drop and basic current carrying capacity of the lines.
5 Safety design of building electrical system
Energy conservation and safety are inseparable. The design of building electricity consumption must ensure the safety of electricity consumption, and there must be no potential safety hazards during use. Safety design needs to be considered from the following aspects. (1) Ensure power supply. Electricity is indispensable in people's daily life, so it is necessary to ensure the continuous supply of electricity. Generally, in order to reduce the trouble caused by unexpected power failure, each high-rise building will prepare two or more independent power supplies to ensure power supply. In addition, high-rise buildings need to be equipped with generators to ensure power supply within 15s after the accident. It is generally stipulated that large-capacity oil-immersed power transformers cannot be used to reduce the occurrence of fires.
(2) Safety of power supply lines and electrical equipment. Due to the large electricity consumption of high-rise buildings, the lines are complicated. Once a fire is caused by excessive line power, the consequences are unimaginable. Therefore, it is necessary to select the conductor and control the current in strict accordance with the specification requirements. In general, high-power electrical equipment should be grounded, and it needs to be grounded repeatedly. Repeated grounding refers to connecting the grounding device with metal wires at one or more places of the neutral line trunk in the system where the neutral point is directly grounded. (3) Building fire protection design. Fire fighting is very important in the electrical engineering design of high-rise buildings. Fire fighting system mainly includes: automatic fire alarm system, fire fighting communication system, fire fighting communication system, fire fighting linkage system and automatic sprinkler system. The materials used in the fire line must have fire prevention function to ensure that the fire line can continue to be used in case of fire. In addition, pumps are generally used for fire fighting, so the control of pumps is also very important.
6 Daily management of electrical safety and energy-saving operation of high-rise buildings
In high-rise buildings, it is very common that non-permanent lamps are in long-term working condition. The staff have a poor awareness of energy saving, and have not developed good habits such as turning off lights, air conditioners, computers and fans. It often happens that air conditioners, computers and other electrical equipment run all day, and the temperature of air conditioners is too high or too low. There are also some large buildings with high power consumption, such as entertainment places, university laboratories, teaching buildings and so on. Lack of effective and safe energy-saving management regulations often leads to huge power consumption and building safety failures. Therefore, it is necessary to cultivate employees' awareness of safety and energy conservation in their daily work. At the same time, the managers of high-rise building electrical system should formulate safe and effective energy-saving and consumption-reducing implementation plans, regularly repair and maintain the entire electrical system, and constantly improve the energy-saving system. Only in this way can we better realize the safety, energy saving and consumption reduction of buildings.
7 conclusion
The requirements for electrical safety and energy saving in future buildings are getting higher and higher, with great potential. In the design process, we should go further into the site, combine with the reality, make it safe and economical, and let people live in a green and low-carbon environment. Over the years, high-rise buildings in Suzhou have adopted the above basic principles and design points of electrical safety and energy saving, which not only did not cause electrical accidents, but also saved a lot of energy and achieved good results.
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