1.
Lightning protection grounding refers to the grounding of lightning protection facilities (such as lightning rods, lightning protection belts, lightning protection nets, and lightning arresters).
2. Foundation grounding refers to using the steel mesh in the underground foundation of the building as the grounding body to replace the artificial grounding electrode.
3. Joint grounding method
The joint grounding method is also called the single-point grounding method, that is, all grounding systems share a common "ground". Joint grounding has the following characteristics:
(1) The grounding system of the entire building forms a cage-type voltage equalizing body. For direct lightning strikes, all points on the same floor in the building are relatively uniform; for induction lightning, the cage-type voltage equalizing body and the frame structure of the building also interfere with external electromagnetic fields. Can provide 10-40dB shielding effect;
(2) The grounding resistance of the general joint grounding method is very small, and there is no coupling effect between various grounding bodies, which is beneficial to reducing interference;
(3) It can save metal materials and occupy less space. It is not difficult to see from the above that the joint grounding method can effectively reduce the interference of external high-voltage transmission lines.
4. Protective grounding: In order to ensure personal safety and prevent indirect electric contact, the exposed conductive parts of the equipment are grounded, which is called protective grounding. There are two forms of protective grounding: one is that the exposed conductive parts of the equipment are directly grounded through their own ground protection wires; the other is that the exposed conductive parts of the equipment are grounded through a common protective wire. 5. Joint grounding within a range is called public grounding.
6. GB50057-2010 defines equipotential bonding as “connecting separate devices, conductive objects, etc. with equipotential bonding conductors or surge protectors to reduce the potential difference generated by lightning current between them.”
Construction needs to be carried out according to the engineering design. The requirements have been stated in the construction drawings. For the practice, please refer to the relevant national standard atlas. The requirements for grounding resistance are generally: direct lightning grounding is less than 10 ohms; independent (dedicated) grounding is less than 4 ohms; joint grounding is less than 1 ohm. Special occasions or equipment with special requirements shall be determined according to their requirements.
1) Working grounding: The grounding required to ensure that electrical equipment meets normal working requirements is called working grounding. In a power system with a directly grounded neutral point, the transformer neutral point is grounded, or the generator neutral point is grounded.
2) Protective grounding: In order to ensure personal safety and prevent indirect electric contact, the exposed conductive parts of the equipment are grounded, which is called protective grounding. There are two forms of protective grounding: one is that the exposed conductive parts of the equipment are directly grounded through their own ground protection wires; the other is that the exposed conductive parts of the equipment are grounded through a common protective wire.
3) Repeated grounding: In a system where the neutral line is directly grounded, in order to ensure safe and reliable protection, in addition to the working grounding at the neutral point of the transformer or generator, necessary grounding is also carried out elsewhere on the protection line, which is called repeated grounding. .
4) Protection connected to the neutral wire: In the 380/220V low-voltage system, since the neutral point is directly grounded, the shell of the electrical equipment is usually connected to the neutral wire, which is called low-voltage protection connected to the neutral wire.
