What are the requirements for electrical equipment grounding?

Standard grounding resistance specification requirements:

1, independent lightning protection grounding resistance should be less than or equal to 10 ohms;?

2, independent safety protection grounding resistance should be less than or equal to 4 ohms;?

3. Independent AC working grounding resistance shall be less than or equal to 4 ohms;?

4, independent DC working ground resistance should be less than or equal to 4 ohms;?

5, anti-static grounding resistance is generally required to be less than or equal to 100 ohms?

6, *** with the grounding body (joint grounding) should be no greater than the grounding resistance of 1 ohms.

Electrical equipment grounding belongs to the safety grounding, if it is independent equipment, should be no greater than 4Ω, if it is a public *** grounding should be no greater than 1Ω.

1, should be grounded part of the

① motors, transformers, switchgear, lighting apparatus, mobile electrical equipment, power tools, metal casing or frame.

② Electrical drive.

③ Electric transformer and current transformer secondary coil (except for relay protection requirements).

④ Indoor and outdoor power distribution devices, consoles and other metal components, as well as near the electrified parts of the metal fence and metal doors.

⑤ Cable terminal box shell, cable metal skin and metal support.

6 Electrical equipment installed on the distribution line tower, such as lightning arrester, protective gap, fuse, capacitor and other metal shells and reinforced concrete towers.

2, do not need to be grounded part

① in the poor conductive ground (wood, asphalt, etc.) in a dry room, when the AC voltage of 380V and below and DC rated voltage of 400V and below, the metal casing of the electrical equipment does not need to be grounded. But when the maintenance personnel for some reason at the same time can touch other electrical equipment has been grounded in other objects, it should be grounded.

② In dry places, when the AC rated voltage of 36V and below and DC rated voltage of 110V and below, the shell of the electrical equipment does not need to be grounded, except in the case of explosive hazards.

③ The metal frame inside the battery compartment with a voltage of 220V and below.

④ If the electrical equipment can be reliably grounded between the electrical equipment and the machine base, only the machine base can be grounded.

⑤ Appliances that can be removed from the grounded metal frame and from the power distribution unit.

The role of grounding is mainly to prevent people from suffering electric shock, equipment and lines suffer damage, prevent fire and prevent lightning strikes, prevent electrostatic damage and ensure the normal operation of the power system.

Grounding is to ensure the normal operation of electrical equipment and personal safety and take a power safety measures, through the metal wire connected to the grounding device to achieve, commonly used protective grounding, work grounding, lightning grounding, shielding grounding, anti-static grounding and so on.

The grounding device will electrical equipment and other production equipment may produce leakage current, electrostatic charge and lightning current into the ground, so as to avoid personal electric shock and possible fire, explosion and other accidents.

Reference:Baidu Encyclopedia-Grounding