The primary distribution box is the main distribution box.

It is generally located at the centralized point of all power supply in the power distribution room control construction site, and is set near the power supply area.

The power supply is connected by the cable leading from the low-voltage side of the electrical transformer on the construction site, and the current transformer, active power meter, reactive power meter, ammeter, voltmeter, main switch and separate switch are installed.

All switches in the main distribution box should adopt knife-melt switches (or leakage protection switches).

The lead-in and lead-out wires should be routed through pipes and have waterproof bends. Construction power distribution cabinet for construction site construction power, is specially designed for the construction site situation is more special, in line with the construction department related construction power standards.

Distribution box (cabinet) is suitable for construction site and outdoor temporary electricity, should meet the "three power distribution, two leakage protection, one machine one gate, one leakage one box" power distribution and protection requirements.

First, basic requirements

(1) The production and manufacturing of the distribution box (cabinet) shall meet the special requirements of the "Low-voltage switchgear and control equipment" Part 4 GB7251.4 for the complete sets of equipment (ACS) for construction sites and the standard requirements of the "Technical Code for Temporary Electricity Safety on Construction Sites" JGJ46-2005.

(2) The installation and use of the distribution box (cabinet) and switch box shall comply with the JGJ46-2005 standard and the GB/T13869 standardized requirements of the "Technical Specifications for Temporary Electricity Safety at the Construction Site" and the "Guidelines for Electricity Safety".

(3) The distribution box (cabinet) and switch box should be divided into N wire and PE wire terminal boards, and the incoming and outgoing cables must be reliably connected through the terminal boards. The N wire terminal plate must be insulated from the metal installation plate. The PE cable terminal board must be electrically connected to the metal installation board. The N wires in the incoming and outgoing wires must be connected through the N wire terminal board. The PE cable must be connected through the PE cable terminal board. The PE cable must be connected to the terminal board by electrical connection. The number of electrical connection points must be two more than the number of circuits in the box. One is the connection point for PE cables entering the box, and the other is the connection point for repeated grounding.

(4) Electrical components should be selected in line with GB/4048.2-2001, GB6829 and JGJ46-2005 standards of products, and in line with the Ministry of Construction "eleventh Five-Year" promotion and application technical requirements.

Second, the main distribution box (cabinet) is equipped with 400A-630A with isolation function DZ20 type transparent plastic case circuit breaker as the main switch, branch setting 4-8 using the DZ20 series 160A-250A transparent plastic case circuit breaker with isolation function, Equipped with DZ20L(DZ15L) or LBM-1 series as a leakage protection device, so that it has undervoltage, overload, short circuit, leakage, phase break protection function, and equipped with two groups of current meter, voltmeter, ammeter. The product of rated leakage action current and rated leakage action time of the leakage protection device is not greater than 30mA.S, it is best to choose rated leakage action current 100-200mA, rated leakage action time is greater than 0.1S, and its action time is delayed action type.