1. Check whether the connecting bolts are loose or rusted.
2. Check the corrosion of the grounding wire and grounding body below the ground, and whether they are desoldered.
3. Check whether the grounding wire is damaged, broken, corroded, etc. For the overhead power lines including the neutral line, the cross-section selection should be as specified: aluminum wire should not be less than 16 mm2, and copper wire should not be less than 10 mm2.
4. To facilitate identification of the different uses of various wires, the phase line, working neutral line and protective line should be distinguished by different colors to prevent the mixing of phase line and neutral line or the mixing of working neutral line and protective neutral line. In order to provide favorable conditions for ensuring the correct wiring of various sockets, a three-phase five-wire power distribution method is used.
5. For the automatic air switch or fuse of the user-side power supply, a single-phase leakage protector should be installed in it. For the user lines that have been in disrepair for a long time, have aged insulation or increased load, or have a small cross-section, they should be replaced as soon as possible to eliminate the hidden dangers of electrical fire and provide conditions for the normal operation of the leakage protector.
6. For the equipment protection grounding wire and neutral wire of the three-phase five-wire system in the power electrical system, no part shall be less than 1/2 of the phase wire in any case. For the lighting system, whether it is a three-phase five-wire system or a single-phase three-wire system, the grounding wire and neutral wire must be the same as the phase wire.
7. The working grounding and protective grounding main lines are allowed to be shared, but their cross-section shall not be less than half of the phase line cross-section.
8. The grounding of each electrical device should be connected to the grounding main line with a separate grounding wire, and several electrical devices that need to be grounded should not be connected in series in one grounding wire.
9. The cross-section of the grounding bare copper wire of the 380V distribution box, maintenance power box, and lighting power box should be >4 mm2, the cross-section of the bare aluminum wire should be >6 mm2, the cross-section of the insulated copper wire should be >2.5 mm2, and the cross-section of the insulated aluminum wire should be >4 mm2.
10. The distance between the grounding wire and the ground should be 250-300mm.
11. The working grounding should be painted on the surface with yellow and green stripes, the protective grounding should be painted on the surface with black, and the neutral line of the equipment should be painted with a light blue mark.
12. The metal skin or metal mesh of the corrugated pipe, the pipe insulation layer, and the metal sheath of the cable shall not be used as grounding wires.
13. When welding the ground wire, lap welding should be used. The lap length must be twice the width of the flat steel (and at least 3 edges are welded), and 6 times the diameter of the round steel (and double-sided welding is required). When the round steel is connected to the flat iron, the lap welding length is 6 times the round steel (and double-sided welding is required).
14. The connection between copper and aluminum wires and the ground bus must be crimped with fixing screws and must not be twisted. When using flat copper soft wire as the grounding wire, the length must be appropriate and the wire nose must be crimped to connect with the grounding screw.
15. During the operation of the equipment, the operating personnel shall check that the grounding wire of the electrical equipment is well connected to the ground grid and the electrical equipment, and there is no breakage that would reduce the cross-section of the grounding wire. Otherwise, it will be treated as a defect.
16. During acceptance inspection of equipment maintenance, it is necessary to check that the grounding wire of the electrical equipment is in good condition.
17. The Equipment Department should regularly inspect the grounding of electrical equipment and promptly notify and rectify any problems found.
18. The grounding resistance of electrical equipment should be inspected and monitored at a prescribed period or during major or minor repairs of the equipment. If any problems are found, the causes should be analyzed and handled in a timely manner.
19. The grounding resistance of high-voltage electrical equipment and grounding grid shall be carried out by the equipment department in accordance with the “Electric Power Equipment Handover and Preventive Testing Procedures”, and the grounding of low-voltage electrical equipment shall be carried out by the department under the jurisdiction of the equipment.
20. The short-circuit current entering the ground of the grounding device is the maximum value of the symmetrical component of the maximum short-circuit current that flows into the ground through the grounding device when a short circuit occurs inside or outside the grounding device. This current should be determined based on the maximum operating mode of the system after 5-10 years of development, and should take into account the short-circuit current distribution between the grounding neutral points in the system and the grounding short-circuit current diverted in the lightning conductor.
Post time: Nov-27-2024