The sum of the grounding resistance of the grounding body or the natural grounding body and the grounding wire resistance is called the grounding resistance of the grounding device. The grounding resistance value is equal to the ratio of the grounding device’s voltage to the ground to the current flowing into the earth through the grounding body. The grounding resistance obtained by the inrush current flowing into the earth through the grounding body is called the impulse grounding resistance; the resistance obtained by the power frequency current flowing into the earth through the grounding body is called the power frequency grounding resistance.

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When a ground fault occurs in the power equipment, the potential difference between the grounded part and the zero potential point of the earth is called the grounding device-to-ground voltage or the grounding device potential.
Possible consequences of poor grounding
1. Broken strands and virtual connections of the grounding wire can easily cause the grounding wire to be burned by a large current or the printed grounding resistance is large, resulting in poor grounding current. The quality inspection of the two does not form a loop, so that the high potential of the high voltage side of the transformer cannot be directly grounded. In addition, maintenance personnel sweat a lot after get off work, the surface resistance of the human body is reduced, and the potential on the transformer is quickly led to the ground through the human body. If it is lethal current, it will cause injury or death of maintenance personnel.
2. When repairing transformers or high-voltage lines, there is no grounding wire installed on the secondary side. If a welding machine or other mobile power generation equipment is used on the secondary side, it is easy to cause the secondary side to return electricity and increase the induced voltage on the primary side of the transformer. The current increases; if someone works on the transformer, the return voltage is high, the current is large, and it is easy to cause injury to personnel.