What are the precautions for reasonable layout of high and low voltage distribution cabinets?
Installation specification of distribution box and reliable use of wiring:
1、 Requirements before use:
1. The distribution box and switch box shall have name, purpose, shunt mark and system wiring diagram.
2. The doors of distribution box and switch box shall be equipped with locks and shall be in the charge of special personnel.
3. The distribution box and switch box shall be inspected and maintained regularly. Inspection and maintenance personnel must be dedicated electricians. During inspection and maintenance, you must wear edge shoes and gloves as required, use electrician edge tools, and make inspection and maintenance records.
4. During regular maintenance and inspection of the distribution box and switch box, the corresponding electric Tan disconnector at the previous level must be opened and powered off, and the power-off sign of "no switching on, someone working" shall be hung. Live work is strictly prohibited.
5. The distribution box and switch box must be operated in the following order:
(1) The power transmission operation sequence is: main distribution box → distribution box → switch box;
(2) The sequence of power failure operation is: switch box → distribution box → general distribution box. However, the emergency of electrical failure can be excluded
6 . When the operation on the construction site is stopped for more than 1 hour, the power switch box shall be powered off and locked.
7 . The operator of the switch box must comply with the provisions of article 3.2.3 of the specification.
8 . No sundries shall be placed in the distribution box and switch box, and shall be kept clean.
9 . Other electrical equipment shall not be hung in the distribution box and switch box at will.
10. The electrical configuration and wiring in the distribution box and switch box shall not be changed at will. When replacing the fuse melt, it is strictly prohibited to replace it with the melt that does not meet the original specification. Before using the leakage protector every day, the technical button of leakage test shall be started for trial tripping times. If the trial tripping is abnormal, it is strictly prohibited to continue to use.
11. The incoming and outgoing lines of the distribution box and switch box shall not bear external forces, and shall not contact with sharp metal fractures, strong corrosive media and inflammables and explosives.
Things and requirements placed in temporary power distribution box, secondary distribution box and tertiary distribution box
In order to implement the Ministry of construction's technical code for reliable temporary power use on construction site (JGJ46-2005), improve and standardize the temporary power distribution box and switch box (ACS) on construction sites in our city, ensure the reliable power use on construction site and prevent electric shock and electrical fire accidents, these rules are formulated in combination with the actual situation of our city.
2、 Setting of distribution box and switch box
1. The power distribution system at the construction site shall be equipped with general distribution box (distribution cabinet), distribution box and switch box to implement three-level power distribution and two-level leakage protection.
2. Several distribution boxes can be set below the main distribution box (distribution cabinet), and several switch boxes can be set below the distribution box.
3. The distribution box and switch box shall be made of cold-rolled steel plate with a thickness of 1.2 ~ 2.0mm. The thickness of the steel plate of the switch box shall not be less than 1.2mm, the thickness of the steel plate of the distribution box shall not be less than 1.5mm, the box door shall be provided with stiffeners, and the surface of the box shall be subject to anti-corrosion treatment. The vertical distance between the center point of fixed distribution box and switch box and the ground shall be 1.4 ~ 1.6m. Mobile distribution box and switch box shall be installed on solid and stable support. The vertical distance between the center point and the ground should be 0.8 ~ 1.6m.
4. The electrical appliances (including sockets) in the distribution box and switch box shall be fastened on the metal electrical installation board without skew and looseness, and then they can be fastened in the distribution box and switch box as a whole. The electrical distribution cabinet (box girder) can also be installed. The metal electrical installation plate and the metal box shall be electrically connected.
5. Copper core edge conductor must be used for the connection of distribution box and switch box. The color of conductor shall be: the color of phase sequence of phase line L1 (a), L2 (b) and L3 (c) shall be yellow, green and red in turn; The color of N line is light blue; The color of PE line is green and yellow. The conductors shall be arranged in order. The branch joints of conductors shall not be crimped with bolts, but shall be welded and bound with edges, and there shall be no exposed live parts.
6. The distribution box and switch box must be equipped with n-line terminal (row) and PE line terminal (row). The n-line terminal (row) must be connected with the metal electrical installation board, and the PE line terminal (row) must be electrically connected with the metal electrical installation board. The number of connection points of n-line terminal strip and PE line terminal strip of the general distribution box (cabinet) shall be n + 1 (n-the number of circuits of the distribution box); At least two or more wiring points of n-wire terminal strip and PE terminal strip of distribution box; The switch box shall be provided with n-wire terminal and PE wire terminal.
7. The metal body of the distribution box and switch box, the metal electrical installation board, and the metal base and shell of the electrical appliances that are normally not charged must be electrically connected with the PE wire through the PE wire terminal board. The metal box door and the metal box must be electrically connected with the soft copper wire.
8. The distance between electrical components on the electrical installation board in the distribution box and switch box shall not be less than 80mm in the vertical direction; The horizontal direction shall not be less than 20mm.
9. The wire inlet and outlet of the distribution box and switch box shall be set at the bottom of the box. The inlet and outlet holes must be protected with rubber wire guard rings, and the inlet and outlet wires shall not be in direct contact with the box; Fixing holes for incoming and outgoing lines shall be reserved on the beam of the box support.
10. The external structure of distribution box and switch box shall be rainproof and dustproof. The protection grade shall not be lower than IP21 when opening the door and IP44 when closing the door.
3、 Selection and configuration of electrical components
1. The electrical appliances of the general distribution box shall have the functions of power isolation, normal connection and disconnection of circuits, as well as short circuit, overload and leakage protection.
The general distribution box (distribution cabinet) is composed of incoming units and outgoing units, or incoming units and several outgoing units. It is equipped with transparent plastic shell general circuit breaker with visible breaking point, transparent plastic shell shunt circuit breaker with visible breaking point and auxiliary power shunt leakage protector which can be automatically disconnected in case of auxiliary power failure. Three point terminal block shall be installed at the output end of each circuit.
2. The number of distribution circuits of the general distribution box (distribution cabinet) is 1 ~ 5 circuits.
3. The distribution box is composed of several incoming units and several outgoing units. It is equipped with the main switch of transparent molded case circuit breaker with visible breaking point, the sub switch of transparent molded case circuit breaker with visible breaking point and the five point wiring terminal board.
4. The number of distribution circuits of the distribution box is 2 ~ 7 circuits.
5. The switch box is composed of incoming units and outgoing units, and is equipped with transparent molded case circuit breaker, leakage protector and five point wiring terminal board with visible disconnection points.
6.. The transparent molded case circuit breakers at the visible breaking points of the main distribution box (distribution cabinet), distribution box and switch box shall be set at the incoming end of the power supply.
7. The general distribution box shall be equipped with voltmeter, general ammeter and watt hour meter. Ammeter and watt hour meter shall not share a set of current transformer. When installing current transformer, the secondary circuit must have a connection point with the protection zero line, and it is strictly prohibited to disconnect the circuit.
8. The rated leakage action current of the leakage protector in the general distribution box (distribution cabinet) shall be greater than 30mA, and the rated leakage action time shall be greater than 0.1s, but the product of the rated leakage action current and the rated leakage action time shall not be greater than 30mA? S。
9. The rated leakage 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 greater than 0.1s.
10. It is strictly forbidden to use plugs and sockets for movable connection at the power inlet of distribution box and switch box.
11. The distribution box and switch box shall have name, purpose, shunt mark and system wiring diagram.
4、 Installation specification and reliable use of distribution box
1. The distribution system shall be equipped with indoor general distribution box and outdoor distribution box or outdoor general distribution box and each distribution box to implement hierarchical distribution.
2. The power distribution box and lighting distribution box should be set separately. If they are combined in the same distribution box, the power and lighting lines should be set separately.
3. The switch box shall be distributed by the final distribution box.
4. The main distribution box shall be located in the area close to the power supply. The distribution box shall be installed in the area with relatively concentrated electrical equipment or load. The distance between the switch box and the distribution box shall not exceed 30m. The horizontal distance between the switch box and the fixed electrical equipment controlled by it should not exceed 3M.
5. The distribution box and switch box shall be installed in dry, ventilated and normal temperature places; It shall not be installed in gas, flue gas, steam, liquid and other harmful media with serious damage. It shall not be installed in places vulnerable to impact, strong vibration, liquid splash and heat source baking. Otherwise, special protective treatment shall be carried out.
6. There shall be enough space and passage for two people to work at the same time around the distribution box and switch box. Do not stack any articles that hinder operation and maintenance; Shrubs and weeds are not allowed.
7. The distribution box and switch box shall be made of iron plate or edge material, and the thickness of iron plate shall be greater than 1.5m.
8. The distribution box and switch box shall be installed correctly and firmly, and the mobile distribution box and switch box shall be installed on a solid support. The vertical distance between the bottom of fixed distribution box and switch box and the ground shall be greater than 1.3m and less than 1.5m, and the vertical distance between the bottom of mobile distribution box and switch box and the ground shall be greater than 0.6m and less than 1.5m.
9. The electrical appliances in the distribution box shall be installed on the non-metallic or wooden edge electrical installation board first, and then fastened in the distribution box as a whole. The metal plate and the iron distribution box shall be electrically connected.
10. The switchgear in the distribution box and switch box shall be fastened on the electrical installation board according to the specified position without skew and looseness.
11. The working zero line in the distribution box and switch box shall be connected through the terminal board, and shall be set separately from the protective zero line terminal board.
12. The connecting wires in the distribution box and switch box shall be edge conductors, and the joints shall not be loose and there shall be no exposed live parts.
13. The metal box of distribution box and switch box, metal electrical installation board and electrical appliances in the box shall not be charged, and the base, shell, etc. must be connected to neutral for protection. The protective zero line shall be connected through the terminal board.
14. The distribution box and switch box must be rainproof and dustproof.
15. The electrical appliances in the distribution box and switch box must be reliable and intact. Damaged and unqualified electrical appliances are not allowed.
16. The main distribution box and distribution box shall be equipped with main disconnector and shunt disconnector, main fuse and shunt fuse (or main automatic switch and shunt automatic switch) and leakage protector. If the leakage protector has the functions of overload and short circuit protection at the same time, the shunt fuse or shunt automatic switch may not be set. The rated value and action setting value of the main switch shall be compatible with the rated value and action setting value of the shunt switch.
17. The general distribution box shall be equipped with voltmeter, general ammeter, general watt hour meter and other instruments.
18. Each electric equipment shall have its own special switch box, and the "machine switch protection" system must be implemented. It is strictly prohibited to use the same switch to directly control more than two electric equipment.
19. The switchgear in the switch box must be able to use electrical equipment for power isolation under any circumstances.
20. Leakage protector must be installed in the switch box, and the installation of leakage protector shall meet the requirements. If the working environment of electric equipment with 36V and below is dry, leakage protector can be avoided.
21. The leakage protector shall 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.
22. The selection of leakage protector shall comply with the requirements of the national standard gb6829-86 leakage current operated protector (residual current operated protector). The rated leakage operating current of the leakage protector in the switch box shall not be greater than 30mA, and the rated leakage operating time shall be less than 0.1s; The leakage protector used in wet and corrosive medium places shall be splash proof products, and its rated leakage action current shall not be greater than 15mA, and the rated leakage action time shall be less than 0.1s.
23. The rated leakage action current and rated leakage action time of the two-stage leakage protector in the distribution box and switch box shall be reasonably matched to make it have the function of hierarchical and sectional protection.
24. The leakage protector must be installed and used according to the product manual. For the leakage protector that has been used for a long time and has been used continuously for months, its characteristics shall be carefully checked, and the problems shall be repaired or replaced in time.
25. Manual switching appliances are only allowed to be used for direct press control of lighting circuits and power circuits with a capacity of no more than 5.5kW. Power circuits with a capacity greater than 5.5kW are controlled by automatic switching appliances or step-down starting devices.
26. The rated value of various switching appliances shall adapt to the rated position of their control electrical equipment.
27. The inlet and outlet of the conductor in the distribution box and switch box shall be set at the lower bottom of the box, and it is strictly prohibited to set on the upper top, side, back or door of the box; The incoming and outgoing lines shall be sheathed, shunted into bundles and made into waterproof bends. The conductor bundle shall not be in direct contact with the inlet and outlet of the box; The incoming and outgoing lines of mobile distribution box and switch box must adopt rubber edge cables.
28. It is forbidden to connect the power line entering the switch box with a pin.
29. All distribution boxes shall be marked with their names, purposes and shunting marks.
30. All distribution box doors shall be equipped with locks, and the distribution box and switch box shall be in the charge of a specially assigned person.
31. All distribution boxes and switch boxes shall be inspected and repaired once a month. Inspection and maintenance personnel must be dedicated electricians. During inspection and maintenance, wear shoes and gloves as required, and use electrician tools.
32. During the inspection and maintenance of the distribution box and switch box, the corresponding power switch at the previous level must be switched off and powered off, and the power-off sign shall be hung. Live working is strictly prohibited.
33. The power transmission sequence of all distribution boxes and switch boxes during use is: main distribution box - distribution box - switch box; The sequence of power failure operation is: switch box - distribution box - general distribution box (except for the emergency of electrical failure).
34. When the construction site stops working for more than hours, the power switch box shall be powered off and locked.