Temporary electricity use plays a vital role in construction site safety management and is one of the most common causes of accidents. Proper management of temporary electrical systems is essential to ensure the safety of workers and reduce the risk of electrical incidents during construction projects.
Construction companies must not connect their own power sources to the public grid, as this can lead to serious safety hazards. For temporary power systems, the 220V/380V three-phase four-wire low-voltage system with a directly grounded neutral point must strictly follow the "Safety Technical Specifications for Temporary Use of Construction Sites" (JGJ46).
All temporary electrical equipment and wiring should be used according to the correct voltage level and capacity. Electrical components must meet national and industry standards, and installation must be carried out in accordance with established electrical codes. Grounding should be properly implemented to ensure safety.
In explosion-prone areas, all electrical equipment, power supplies, and wiring must meet the required explosion-proof standards, and appropriate safety measures must be taken to prevent accidents. The grounding and protection systems for temporary electrical equipment must comply with regulations. The protective earth wire (PE wire) should be an insulated conductor with a minimum cross-sectional area that meets code requirements. It must not have switches or fuses installed. The working neutral wire (N wire) must pass through a residual current device (RCD), and there should be no direct electrical connection between the N wire and PE wire after the RCD.
The insulation of all temporary electrical lines and equipment must be intact and in good condition. All temporary power cables must be rubber-sheathed insulated cables to ensure durability and safety. Overhead temporary power lines should be made of insulated copper conductors and installed on dedicated poles, avoiding trees and scaffolding. The lowest sag of overhead lines should be at least 2.5 meters above the ground within the construction area and at least 5 meters over motor vehicle lanes.
For underground cable installations, clear markers and safety signs should be placed along the route. Cables should be buried at a depth of no less than 0.7 meters, and protective casings should be added when crossing roads.
On-site temporary power distribution panels and boxes should be clearly labeled and protected from rain. They should be installed at least 30 cm above the ground, and the doors and covers should be securely closed. When connecting or removing temporary power lines from a switch, the upper switch should be turned off, and a warning sign should be displayed to prevent accidental energization.
A double-winding safety isolating transformer must be used for lighting transformers, and fuses should be installed appropriately. The voltage of portable lights should not exceed 36V. In special environments such as wet areas or metal containers like towers, tanks, and vessels, the voltage of temporary lighting should not exceed 12V.
The selection and installation of residual current devices (RCDs) for temporary power lines must meet the requirements of GB6829 and GB13955. All temporary power facilities should follow the "one machine, one switch, one protection" principle. Switch boxes and portable or handheld tools must be equipped with RCDs that meet the specifications to ensure electrical safety.
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