I. Introduction

Low-voltage distribution box is the lowest level of control and protection facilities in the power system, and is the most basic link to ensure the safe operation of the power system. It has a great opportunity to contact with workers, but because of its large number, wide distribution, and mostly low-value products, it is often ignored by the equipment power department, so that many low-voltage distribution boxes are out of control, resulting in unsafe factors, increasing the risk of personal shock and electrical fire. Therefore, the safe selection and use of low-voltage distribution box must attract our attention.

Second, the selection of low-voltage distribution box protection type

The protection type of low-voltage distribution box should be selected according to the conditions of the workplace.

(a) In the relative humidity does not exceed 75%, and there is no dust, no corrosive gas or vapor, no flammable and explosive substances less dangerous places, the low-voltage distribution box can be selected open-type.

(b) In particularly humid places with relative humidity close to 100% and places with corrosive gases or vapors, protective types should be selected.

(c) Dusty places that can produce a lot of dust should be dustproof distribution boxes.

(d) In the flammable liquid and suspended, accumulated flammable dust or flammable fiber H-1, H-2 fire danger places, should be selected dust-proof type; In the presence of solid combustible material H-3 fire hazard places, optional protection type.

(e) The selection of explosive dangerous places.

(f) where there is an explosive mixture of gases or vapors

① Under normal circumstances can form an explosive mixture of Q-1 level places should be selected flameproof, explosion-proof ventilation, inflatable low-voltage distribution box.

② In normal circumstances can not be formed, and in abnormal circumstances can form an explosive mixture of Q-2 places, you can choose any explosion-proof type.

③ In normal circumstances can not be formed, and in abnormal circumstances can form explosive mixtures but less likely Q-3 places, can choose sealed type.

(2) In places with explosive mixtures of dust or fibers.

① G-1 places that can form explosive mixtures under normal circumstances can choose any level flameproof type, explosion-proof ventilation type, and inflatable type.

② G-2 grade places that cannot be formed under normal circumstances and can form explosive mixtures under abnormal circumstances can be dustproof.