The metal casing of the electrical equipment is grounded, and it is not handled casually. It is a grounding body or grounding device that is buried in the ground according to certain requirements. The grounding device includes two parts: a grounding pole and a grounding wire.
The grounding pole is generally made of metal such as steel pipe, steel bar and angle iron; the grounding wire is the connecting line between the grounding pole and the outer casing of the electrical equipment.
1. Grounding pole: If steel pipe is used, its diameter is generally 20~50mm; the diameter of steel bar is 10~12mm; the angle iron is 20×20×3 or 50×50×5mm. The length is about 2.5 to 3 m. Buried vertically underground.
2. Grounding wire: bare copper wire, aluminum wire and steel wire can be used as grounding wire. It is best not to use aluminum wire easily. The cross section of the copper wire shall not be less than 4 mm2, and the cross section of the aluminum wire shall not be less than 6 mm2. The grounding wire and the grounding electrode are preferably connected by soldering. When bolted to the equipment, it must be tightened with bolts.
In order for the grounding device to function, the key is that the grounding resistance Rd is small, and it is generally required to ensure that the grounding resistance Rd is not more than 10 ohms. Sometimes it is affected by the factors such as the groundwater level of the soil, and the grounding resistance is too large to ensure the required value. Therefore, the number of polar roots can be appropriately increased (the distance between the ground electrodes is not less than 2.5 m), the soil can be buried with some clay, and a mixture of salt and charcoal can be appropriately added.
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