The construction site is inseparable from electricity, as well as engineering equipment, construction machines and tools, on-site lighting and electrical installation. Need the support of electric energy. With the strengthening of science and technology content and intelligence of building engineering, the degree of mechanization and automation of construction has been continuously improved, and the places where electricity is used are more extensive. However, while electric energy brings convenience to human beings, it also has powerful destructive power. Due to the characteristics of various types of electrical equipment, large capacity, unstable working environment, open-air operation, temporary use, etc., short-term behavior is easy to exist in the laying of electrical lines, the selection of electrical components, cables, circuit settings, etc., which is easy to cause electric shock casualties. Therefore, it is an important aspect to ensure the construction safety to strengthen the management of temporary electricity consumption and use electricity according to the specifications. Temporary power consumption system in construction site can be summarized into five principles to understand and operate. First, the principle of one circuit and one circuit on the construction site Temporary electricity consumption on the construction site must be organized and designed in a unified way, with a unified construction plan for temporary electricity consumption, a power supply, and a construction, installation, maintenance and management team for temporary electricity consumption. It is forbidden to connect the lines privately and take more electricity; It is forbidden to use construction machinery and lighting independently from different power sources. As the first person in charge of production safety on the construction site, the project manager should equip and use electrical technicians who have been trained in the basic knowledge of safe electricity use, understand the performance of the equipment used and have the qualification to work, establish complete technical data on temporary electricity use safety, establish a regular inspection system, and keep records of daily maintenance, resistance test and electrician maintenance of electrical equipment. After the construction of temporary electricity utilization project is completed, a comprehensive inspection and acceptance must be conducted. The main problems that often appear in the construction site are that there is no temporary electricity utilization construction organization design, or although there is temporary electricity utilization construction organization design, the compilation procedures are incomplete, the contents are empty, copying the specifications can not guide the construction, it is out of touch with the actual situation on site, there is no electricity maintenance inspection system, the electricity utilization test data is filled out out of thin air, and the electrician lacks power distribution knowledge. Second, the principle of two-level protection for temporary electricity consumption "Technical Specification for Safety of Temporary Electricity Consumption on Construction Site" requires that all electrical equipment on the construction site must be equipped with a leakage protection device at the head end of the equipment load line in addition to the protection of zero. At the same time, it is stipulated that leakage protectors must be installed in the switch box. That is to say, temporary electricity consumption should be provided with leakage protectors in the main distribution box and switch box respectively to form two-level protection of power lines. The leakage protector should be installed on the load side of the power disconnector of the distribution box and the load side of the power disconnector of the switch box. The protection area of the total distribution box is large, and the influence scope after power failure is also large, mainly to provide indirect protection and prevent leakage fire, and its leakage action current and action are greater than the following protection. Therefore, the rated current action and rated leakage action time of two-stage leakage protectors in the main distribution box and switch box should be reasonably coordinated, so that they have the functions of classification and subsection protection. The action current of the leakage protector in the switch box shall not be greater than 30mA, and the rated leakage action time shall not be less than 0.1s.. For the leakage protector that has been put on hold for a long time and continuously used for one month, its characteristics should be carefully checked, and the problems should be repaired or replaced in time.
Third, the three-level distribution principle The distribution system should be equipped with a general distribution box, a distribution box and a switch box. According to the transmission sequence of main distribution box-distribution box-switch box, a complete three-level power system is formed. This way, the distribution level is clear, which is convenient for management and fault finding. The main distribution box should be located near the power supply. The distribution box should be installed in the place where the electrical equipment or load is relatively concentrated. Power distribution box and lighting distribution box should usually be set separately. The distribution box and switch box should be installed in a dry, ventilated and normal temperature place, far away from places vulnerable to external solid objects and strong vibration, or for environmental protection. The distance between distribution box and switch box shall not exceed 30m. The horizontal distance between the switch box and the fixed electrical equipment it controls shall not exceed 3m. Around the distribution box and switch box, there should be a space and passage for two people to work at the same time. Don't hinder the operation and maintenance because of stacked items and sundries, or weeds and uneven environment. The electrical box should also have doors, locks, rain and dust prevention measures.
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