Keywords distribution line; Distribution mode; Installation technology; fire precautions
order
In building electrical engineering, distribution line design is a very important link, which is related to the rationality of electricity consumption in the whole building and one of the important factors to ensure the safety of the whole building project. In the process of electrical distribution line design, the choice of distribution mode must be determined according to the actual situation and demand of the whole building. If the distribution mode is not standardized or the distribution construction is unreasonable, or no effective protection measures are taken for the distribution lines, it is easy to cause accidents. At the same time, in the process of electrical wiring construction, fire prevention measures must be taken to reduce the occurrence of fires through effective control and improve the fire prevention ability of building electrical distribution lines. In the process of building electrical engineering construction, the construction unit should also attach great importance to it, carry out construction in strict accordance with the requirements of design and relevant specifications, strengthen on-site management, ensure the construction quality and safety of electrical distribution lines, and provide a comfortable and safe living environment for people.
1. Distribution mode of building distribution lines
In the construction of building distribution lines, it is very important to choose a reasonable distribution mode. Only by being familiar with and mastering the specific situation of load can we deeply understand and understand the distribution mode. According to the demand of electricity load, the distribution load of civil buildings can be divided into three grades. High-rise and super-high-rise large buildings, stadiums, etc. , with large scale and high power consumption, belongs to the first-class load, and its distribution mode is mainly 10KV, also known as medium-voltage distribution.
380V/200V power distribution is low-voltage power distribution, which is mainly used in some small civil buildings. Power users are directly connected to the local 380V/200V low-voltage power grid, and the distribution radius is generally less than 250 meters, which can meet the power demand of construction projects. There are three kinds of power distribution modes commonly used in high-rise buildings: radial, trunk and hybrid, among which the hybrid partition power distribution mode is widely used. Its advantages are as follows: 1)I is used as power supply, and standby power supply can also be used as partition trunk line or bottom-up vertical trunk line. 2) The working power supply and standby power supply are vertical trunk lines from bottom to top. 3) The working power supply is partitioned trunk line, and the standby power supply is taken from the emergency power supply trunk line. When supplying power to each distribution point on the floor, it is suggested to adopt sub-regional main distribution, but some concentrated loads or important loads with large capacity should be distributed radially from the low-voltage distribution room.
Second, the problems that should be paid attention to in the installation of distribution lines
The transmission system of EDB is complex, and the reliability of distribution lines is particularly important to ensure the good operation of distribution system. According to my experience in installing distribution lines in high-rise buildings, I should pay attention to the following aspects when installing distribution lines:
1. Correct selection of cable and wire materials for distribution lines
In order to ensure the safety of distribution lines, we attach importance to solving problems from the source and making a good choice of cable and wire materials. On the one hand, strictly select flame-retardant cables and wires that meet the requirements of raw material standards and relevant specifications, especially in terms of material specifications and wire length, to meet the requirements of construction design; On the other hand, pay attention to the performance of cables and the fire and high temperature resistance of wires, and try to choose cables with insulating materials for construction and laying. For some building areas with high fire protection requirements, we give priority to the use of higher standards of non-combustible cables, which is a kind of cable with better fire protection performance. Its main protective sleeve is copper or magnesium oxide powder as insulating copper core, which can effectively reduce the occurrence of fire accidents. Even if the distribution line is on fire for other reasons, the incombustible cable will use its own fireproof and insulating characteristics to control the fire spread. Besides, this kind of incombustible cable can be used for a long time. In daily use, it has certain resistance to the corrosion of some water, oil, smoke and so on. It is worthy of being widely used in future building distribution lines.
2. Selection and laying technology of dense plug-in bus duct
Because the project is a high-rise building with a large scale, it also puts forward higher requirements for power load density. In order to fully meet the needs of this high-density load, our company gives priority to dense plug-in busways when installing distribution lines to meet the power supply. This bus duct consists of a shell and a group of parallel flat conductors arranged in the shell, and the outside is covered with insulating material. It has the characteristics of small occupied space, compact structure, good grounding, safety and reliability, and high electrical and mechanical properties. Because of its unique wiring mode, its wiring process is relatively simple and convenient. The phase line and zero line of the same circuit are laid in the same metal trunking. The trunking has a certain margin, and there is no joint. Conductors shall be bound in sections according to the number of turns, and the binding spacing shall not be more than 2m. Lines without anti-interference requirements in different circuits of the same power supply can be laid in the same trunking. Lines with anti-interference requirements should be separated by partitions or shielded wires, and one end of shielding sheath should be grounded. When multi-phase power supply is adopted, the insulation color of wires should be consistent with the requirements of specifications, that is, the protective ground wire (PE wire) should be yellow-green, the neutral wire should be light blue, and the phase wire should be ll yellow, L2 green and L3 red.
3. Installation technology of distribution line cable tray
Cable bridges are generally composed of brackets, supporting arms and installation accessories, and there are different structural types such as trough type, tray type, ladder type and net type. When I designed the bridge layout, I comprehensively considered the technical feasibility, economic rationality, operational safety and other factors, and tried to show its characteristics of beautiful shape, simple structure, convenient configuration and easy maintenance. Bridges in the building will be erected on the supports of nearby buildings and pipe corridors, and some places will be erected independently. Distance between horizontal mounting brackets of cable tray: 1.5-3m, and distance between vertical mounting brackets: no more than 2m. The distance between the top cable bracket and the top of the shaft or floor shall not be less than 150-200mm, and the bottom of the bottom cable bracket or the ground shall not be less than 50- 100mm. It is forbidden to weld metal conduits, and galvanized and steel conduits with wall thickness less than 2mm shall not be welded with sleeves. The steel conduit shall be laid under the outdoor ground, with a buried depth of not less than 0.7m and a wall thickness of not less than 1l or 2mm. When there is no requirement in the design, the conduit buried in the wall or concrete should be medium or above. At the same time, we will galvanize all the bridge installed outdoors, which can effectively improve the service life of cable bridge and reduce the maintenance frequency to some extent.
Three, electrical distribution line fire prevention measures
Distribution line is used to transmit electric energy, which has the characteristics of long line, many branches, wide application range, easy contact with combustible substances, difficult to find common faults, and rapid spread of insulation fire. Circuit fires are mainly caused by short circuit, leakage, overload, excessive contact resistance or arc, electric spark or high temperature and high heat caused by insulation breakdown. I put fire prevention measures in the first place when distributing electricity to buildings, and strive to control the probability of fire and accidents caused by distribution lines to a minimum.
1. Methods to control fire spread
Electrical fires in buildings are extremely destructive and dangerous, which are easy to spread mainly through direct combustion of combustible materials, heat conduction, heat radiation and heat convection, and eventually cause huge losses. Therefore, when there is a fire in the building distribution line, we should pay attention to the following problems: when dealing with the fire, we should first consider how to control and deal with the fire spread. First of all, cut off the power supply, cut off the flame and combustible materials in time to prevent the spread of disasters. Generally speaking, the design of closed metal trunking is often used to prevent the fire from spreading when electric fire occurs. At the same time, it is also necessary to prevent the short circuit that may occur in the actual construction of distribution lines in construction projects, and effectively prevent the occurrence of electric energy fire accidents in buildings. .
2, completes the interlayer fire prevention measures
Because the building is large and can accommodate a large number of people, I give priority to the protection between different functional areas and floors when designing the special fire protection scheme for distribution lines. When a fire breaks out, it usually spreads between the same floors, which eventually leads to serious consequences. Therefore, it is necessary to focus on interlayer fire prevention treatment, such as setting firewall F, fire partition and fire interlayer, to improve the fire prevention performance of buildings. In case of fire, immediately organize personnel to evacuate in an orderly manner and put out the fire quickly. Select the appropriate fire extinguisher according to the characteristics of the site fire. The extinguishing agents of carbon dioxide fire extinguishers and dry powder fire extinguishers are not conductive and can be used for live fire extinguishing. The fire extinguishing agent in foam extinguisher has certain conductivity, which affects the insulation of electrical equipment and is not suitable for live fire extinguishing. When using a water gun to put out the fire, in order to ensure safety, a spray water gun is used. When using ordinary DC water gun to put out the fire, in order to prevent the leakage current passing through the water column from passing through the human body, the nozzle of the water gun can be grounded, and firefighters can also wear insulating gloves, insulating boots or work clothes to keep the human body at a necessary safe distance from the charged body.
3. Improve fire prevention technology and material control.
Distribution line fire accounts for a relatively high proportion in building electrical fire incidents, and some building distribution lines are prone to dangerous accidents due to aging due to time problems or poor quality of line selection during construction. When external factors are encountered, such as power overload, excessive voltage load, mechanical damage of line insulation shell, lightning strike, etc. , or because of weak insulation of electrical lines being broken down, resulting in single-phase or multi-phase short circuit and igniting combustible substances nearby, a fire will occur. In order to avoid the above situation and promote the effective improvement of the overall fire protection performance of building projects, designers should combine the specific environment and scientific knowledge, and combine the use of advanced fire protection materials and technologies. Fire-proof and heat-insulating layer on the surface of combustible materials in distribution lines can minimize the influence and spread of fire in the event of short circuit and other dangerous situations. China attaches great importance to the fire prevention treatment of building distribution lines, and constantly researches and invents novel, scientific and environmentally friendly fire prevention technical materials. Designers must also persist in learning advanced fire prevention skills, understand new fire prevention materials, and apply them to the actual construction of distribution lines in construction projects to promote the continuous improvement of fire prevention performance of distribution lines in construction projects.
Four. Concluding remarks
At present, in the construction of building electrical distribution lines in China, the first consideration is mainly the distribution mode of distribution lines and the implementation of fire prevention measures. The construction quality of building electrical distribution lines directly affects the later life of residents. If the selection method of building electrical distribution lines is unreasonable or there are problems in the implementation during the power distribution construction, it will directly affect the later use of the building, and even cause short circuit to cause fire, endangering the safety of residents' lives and property. Therefore, construction enterprises should strengthen management and quality control during the implementation of building electrical distribution lines, strictly supervise the construction quality, and ensure the safety of building electrical distribution lines in buildings.
refer to
Yang Zhigang, 1, On the Cause Analysis and Maintenance Measures of Operation Faults of Distribution Lines [a] .2065438+Proceedings of 2004 National Science and Technology Work Conference [c] .20638+2004.
2 Hou Yue, Fault Analysis and Prevention of lOkV Distribution Line [J]. Inner Mongolia Petrochemical Company, 2065438+24, 2005.
3 Liu An. Cause analysis and preventive measures of building electrical fire j, scientific and technological information, 20 12, 19.