The grade distribution box is the main distribution box.
It is generally located in the power distribution room to control all power supplies at the construction site, and is located near the power supply area.
The power supply is connected by cables drawn from the low-voltage side of the electric transformer at the construction site, and current transformers, active energy meters, reactive energy meters, ammeters, voltmeters, main switches, and sub-switches are installed.
All switches in the main distribution box should use knife fusion switches (or leakage protection switches).
The incoming and outgoing wires should pass through pipes and have waterproof bends. The first-level power distribution cabinet for construction power is used for power consumption on construction sites. It is specially designed for the special conditions of the construction site and complies with the relevant construction power specifications and standards of the construction department.
Distribution boxes (cabinets) are suitable for temporary power use at construction sites and outdoors, and should meet the power distribution and protection requirements of "three-level power distribution, two-level leakage protection, one machine, one gate, one leakage, one box".
1. Basic requirements
(1) The production and manufacturing of distribution boxes (cabinets) should comply with the special requirements for complete sets of equipment (ACS) for construction sites (ACS) in Part 4 of "Low-voltage Switchgear and Control Equipment" and "Safety Technology for Temporary Electricity Use at Construction Sites" Specification" JGJ46-2005 standard requirements.
(2) The installation and use of distribution boxes (cabinets) and switch boxes should comply with the "Technical Specifications for Temporary Electricity Safety at Construction Sites" JGJ46-2005 standards and the "Electricity Safety Guidelines" GB/T13869 standardization requirements.
(3) The distribution box (cabinet) and switch box should be equipped with N line and PE line terminal boards respectively. The incoming and outgoing lines must be reliably connected through the terminal board. The N line terminal board must be insulated from the metal electrical installation plate; the PE line terminal board must be electrically connected to the metal electrical installation plate. The N line in the incoming and outgoing lines must be connected through the N line terminal board; the PE line must be connected through the PE line terminal board. The connection between the PE wire and the terminal board must be electrical. The number of electrical connection points should be 2 more than the number of loops in the box. One is the connection point for the PE wire entering the box, and the other is the connection point for repeated grounding.
(4) Electrical components should be products that comply with GB/4048.2-2001, GB6829 and JGJ46-2005 standards, and comply with the technical requirements for promotion and application of the Ministry of Construction's "Eleventh Five-Year Plan".
2. The main distribution box (cabinet) is equipped with a 400A-630A DZ20 transparent molded case circuit breaker with isolation function as the main switch, and 4-8 branches are set up using DZ20 series 160A-250A transparent molded case circuit breaker with isolation function. The device is equipped with DZ20L (DZ15L) or LBM-1 series as a leakage protection device, so that it has under-voltage, overload, short circuit, leakage, and phase failure protection functions. It is also equipped with two sets of current mutual sinks for watt-hour meter, voltmeter, and ammeter. The product of the rated leakage action current and the rated leakage action time of the leakage protection device is not greater than 30mA.S. It is best to use a rated leakage action current of 100-200mA, a rated leakage action time greater than 0.1S, and its action time is a delayed action type.