Distribution box is the lowest level of control and protection facilities in the power system. It 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 most of the low-value goods, often ignored by the power department of equipment, so that many distribution boxes are out of control, resulting in unsafe factors, increasing the risk of personal electric shock and electrical fire. Therefore, we must pay attention to the safe choice and use of distribution box.
The electrical components and installation of the distribution box must comply with the relevant safety provisions in the "Code for the Design of Low-Voltage Distribution Devices and Circuits" and the "Code for the Construction and Acceptance of Electrical Installation Engineering". The working voltage, current, frequency and grade of the electrical components used in the distribution box must meet the working requirements. In addition, each branch or protection of the distribution box needs to have a choice of places, but also should be equipped with special protection appliances. At the same time, when the fuses are used to protect the distribution lines, the fuses should be installed on the poles of ungrounded phases. When the fuses of distribution boxes are used for short-circuit protection, the sections of the melts or conductors should conform to the corresponding regulations. When a distribution box uses automatic switches to protect distribution lines, its overcurrent trippers shall be mounted on ungrounded phase poles. If the distribution box uses an automatic switch with only a transient or short-delay overcurrent trip, the setting current of the trip should avoid the short-time overload current.
In some dangerous places of fire and explosion and distribution lines that may be overloaded for a long time, distribution boxes should be equipped with overload protection devices. The allowable current carrying capacity of insulated conductors and cables of distribution lines should be greater than the rated current of fuse melt or 1.25 times of the long-delay overcurrent tripping setting current of automatic switches. Strict management and correct use of distribution box city to reduce electrical accidents indispensable measures, to do a good job of its management and use, must carry out the principles of hierarchical management, line management, clear system, each has its own responsibility.
