Temporary use of electricity refers to the temporary application of electrical power in a specific location, typically involving the setup of temporary electrical equipment and substations. The distribution boxes at all levels are branched out to their respective power sources.
The distribution box is categorized into three types: first-level distribution boxes, second-level distribution boxes, and third-level distribution boxes.
The first-level distribution box introduces three-phase power, ground, and neutral from the transformer. It is commonly used for construction site power supply and is specifically designed to meet the standards of the construction industry. These units can form a complete three-level protection system, ensuring safety by providing one machine, one circuit breaker, and one leakage protection. The first-level cabinet features a lower exit design, with the front door opening for easy access. The main busbar is connected via copper bars, ensuring good contact and a safe internal layout. The rainproof top makes it suitable for field operations.
The second-level distribution box receives power from the primary distribution box and distributes it to the temporary power points. It is also designed for construction sites and follows the relevant electrical safety standards. This type of box often has both internal and external doors, with an exterior coated in plastic for durability and aesthetics. It should be placed 1.5 meters above the ground, with a main switch rated between 60A and 100A (e.g., DZ47-63). Other switches include lighting (16A), air conditioning (20A), and electric water heater (60A) circuits, each equipped with a two-phase leakage protector. The main switch typically does not have leakage protection, but branch switches do, as human body exposure to 30mA is dangerous.
The third-level distribution box is the control unit directly connected to the electrical equipment. It serves as the final stage of power distribution, ensuring that each device has its own dedicated circuit. This setup helps prevent overloading and enhances safety. The principle of "one machine, one switch, one leak, one box, one lock" is strictly followed, prohibiting the use of a single switch to control multiple devices.
The key differences between the three levels are as follows:
1. First-level distribution boxes receive power directly from the transformer.
2. Second-level boxes distribute power from the first-level boxes to the point of use.
3. Third-level boxes control individual electrical equipment.
In larger systems, such as residential buildings, power distribution is organized in levels. For example, a building’s main distribution box is the first level, while the unit-specific boxes are second-level, and the household-level boxes are third-level. This structured approach ensures efficient and safe power delivery.
Understanding these distinctions is essential for proper installation, maintenance, and compliance with electrical safety regulations. Whether on a construction site or in a residential area, using the right distribution system can significantly improve efficiency and reduce risks.
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