Electrician - Basic Knowledge of Safe Operation for Construction Workers

Author: Construction Ministry's Department of Engineering Quality and Safety Supervision and Industry Development, All-China Federation of Trade Unions, China Seafarers' Construction Trade Union
Publisher:
Publish Date: 2006-06-01
Features:
II. Basic Knowledge of Safe Operation
1. In the dedicated transformer neutral point directly grounded circuit at the construction site, the factory N-S zero-protection system must be adopted.
2. The start, middle, and end of power supply lines at the construction site must be repeatedly grounded. Repeated grounding must be performed in areas with concentrated equipment (e.g., batching plant sheds, steel bar working areas) or at high-elevation equipment (e.g., tower cranes, external elevators, material hoists).
3. The metal casings of electrical equipment must be protected with grounding.
4. In the same power supply system, it is not allowed for some equipment to be grounded while others are zero-protection grounded.
5. The insulation of all electrical equipment and circuits at the construction site must be in good condition, and connections must not be exposed.
6. When indoor lighting is less than 2.5 meters above the ground and outdoor lighting is less than 3 meters above the ground, the power supply voltage should not exceed 36 volts.
7. Handheld lighting (portable lamps) should use a safety voltage of no more than 36 volts. In damp or easily accessible areas with live electrical parts, lighting should use a safety voltage of less than 24 volts. In particularly damp areas, conductive surfaces, or metal containers, lighting should use a voltage of no more than 12 volts.
8. The distance between tungsten halogen lamps, spotlights, and flammable materials should not be less than 500 millimeters, and they must not directly illuminate flammable materials. If the requirements are not met, heat insulation measures must be taken.
9. Tungsten halogen lamp power cables should use three-core rubber-insulated cables. For outdoor use, rainproof measures must be provided. Insulation must be installed on the handle of mobile brackets, and the casing must be grounded.
10. The main distribution box should be placed near the power source. The sub-distribution box should be placed in areas with relatively concentrated power consumption or loads. The distance between the sub-distribution box and the switch box must not exceed 30 meters.
11. There must be enough space and access for two people to work simultaneously around the switch box, with a fence and rainproof measures. No should be stacked around the box.
12. A leakage protector must be installed in the switch box, with a rated leakage action current not exceeding 30 milliamperes and a rated leakage action time not exceeding 0.1 seconds. Splash-proof leakage protectors must be installed in outdoor, damp, corrosive environments, or when operating on metal structures.
13. Handheld electric tools must be equipped with leakage protectors with a rated leakage action current not exceeding 15 milliamperes and a rated leakage action time not exceeding 0.7 seconds.
14. Switch boxes must be installed around the controlled power-consuming equipment and in easily accessible locations, with a horizontal distance to the fixed power-consuming equipment they control not exceeding 3 meters.
15. The vertical distance from the center of the fixed distribution box to the ground should be 1.4–1.6 meters. The vertical distance from the center of the mobile distribution box to the ground should be 0.8–1.6 meters.
16. When the distribution cabinet or power supply line is shut down for maintenance, grounding wires must be installed, and a "No Power Switching—Work in Progress" sign must be hung. Power shutdown and restoration must be handled by a designated person.