Electrical grounding: Grounding refers to the neutral point of the power system and electrical installations, the exposed conductive parts of the electrical equipment and the conductive parts outside the device are connected to the earth via conductors, and the lightning, faults, and leakage currents are quickly led to the earth to ensure the safety of equipment and personal , Electrical grounding can be divided into many types according to different properties, the common ones are working grounding, lightning protection grounding and protective grounding.

Protective grounding is to prevent equipment from endangering personal or equipment safety due to insulation damage and electrification. For example, the metal shell of power equipment, reinforced concrete poles and metal poles. Protective grounding will only flow when the equipment insulation is damaged. The size is directly related to the device itself and the degree of failure.

Lightning protection grounding is to eliminate the dangerous effects of overvoltage, such as the grounding of lightning rods, lightning conductors and lightning arresters, whether in substations, booster stations, railway systems or general residential buildings. The main function is to prevent lightning The impact of the impact on the protection of electrical appliances and personnel.

When we use electrical equipment, the chassis grounding is also a typical protective grounding. The function is the same to prevent the safe operation of equipment and personnel.

Qualified standards for lightning protection and grounding

The grounding device for lightning protection induction should be shared with the grounding device of electrical equipment, and its power frequency grounding resistance should not be greater than 10Ω.

The grounding resistance of each down conductor is not less than 10Ω, and the grounding device for preventing direct lightning strikes should share the grounding device with lightning protection induction, electrical equipment, information system, etc.

Lightning arresters, cable metal sheaths, steel pipes and insulator iron feet, fittings, etc. should be connected to the ground, and their impulse grounding resistance should not be greater than 10Ω.

Overhead and directly buried metal pipelines should be connected to the lightning protection grounding device nearby when entering and exiting the building. When not connected, the overhead pipeline should be grounded, and its impact grounding resistance should not be greater than 10Ω.

The impulse grounding resistance of each down conductor should not be greater than 30Ω.

The lightning arrester, the metal sheath of the cable, the iron feet of the insulator, and the fittings should be grounded together, and the impulse grounding resistance should not be greater than 30Ω.