What are the types of grounding?
Grounding refers to the neutral point of the power system and electrical equipment, the exposed conductive parts of electrical equipment, and the conductive parts outside the device being connected to the ground through conductors. It can be divided into working grounding, lightning protection grounding, protective grounding, anti-static grounding, shielding grounding, repeated grounding, and isolation grounding.
1. Working grounding: The grounding carried out to ensure the reliable operation of electrical equipment under normal and accident conditions. The neutral grounding of generators and transformers is mainly used to strengthen the stability of low-voltage system potential and reduce the risk of overvoltage caused by one phase grounding, high and low voltage short circuiting, and other reasons.
2. Lightning protection grounding: Lightning protection grounding is a grounding system used to prevent damage when subjected to lightning attacks (direct strikes, induction, or line introduction). Grounding for lightning protection equipment (lightning rod, lightning conductor, lightning arrester, etc.). For direct lightning strikes, lightning protection devices (including overvoltage protection grounding devices) promote the neutralization of positive charges in thunderstorms and ground induced negative charges to prevent the occurrence of lightning strikes; For static induction lightning, the static charge generated by induction is used to quickly introduce them into the ground, in order to avoid the danger of spark discharge or local heating causing the combustion and explosion of flammable or explosive materials.
3. Protective grounding: It is a method of reliably connecting the metal parts of electrical appliances (i.e. the metal structure parts that are insulated from the live parts) that are not normally charged but may be charged in the event of insulation material damage or other circumstances, with wires to the grounding body to protect people. To ensure personal safety and avoid electric shock accidents, the method of connecting the metal shell of electrical equipment to the grounding device is called protective grounding. When the human body comes into contact with electrical equipment with a charged shell, due to the contact resistance of the grounding body being much smaller than the human body's resistance, the vast majority of current enters the ground through the grounding body, and a small portion flows through the human body, which does not pose a threat to human life.
4. Anti static grounding: To prevent the harmful effects of static electricity and discharge it, it is an important part of static electricity protection. When equipment moves or objects flow in pipelines, static electricity is generated due to friction, which accumulates on pipelines, containers, and storage or processing equipment, forming a high potential and posing a danger to personal safety and equipment and buildings. As an electrostatic grounding device, once static electricity is generated, it is introduced into the ground to eliminate the possibility of its accumulation.
5. Shielding grounding: It is an effective measure to eliminate the harm of electromagnetic fields to human health and also an effective measure to prevent electromagnetic interference. To prevent electromagnetic interference, a good electrical connection made between the shielding body and the ground or the metal shell of the interference source is called shielding grounding. Setting shielding devices on the equipment casing that generates magnetic fields and grounding the shielding body can not only reduce the intensity of electromagnetic fields outside the shielding body, achieve the goal of reducing or eliminating the harm of electromagnetic fields to human health, but also protect the equipment inside the shielding grounding body from the interference and influence of external electromagnetic fields.
6. Repeated grounding: When there is a shell collision or grounding short circuit in the system, the voltage of the zero line to ground can be reduced; When the zero line breaks, the degree of fault can be reduced.
7. Isolation grounding: Limiting the electric field generated by the interference source to the interior of the metal shield, preventing the external environment from being affected by the interference source inside the metal shield.