Electrical equipment housing grounding standard

Update date:2018-06-27 Source:MAXGE

Electrical connection of certain points in live parts of electrical installations or electrical circuits and earth connection, electrical installations or other devices in normal state when there are no live parts of an artificial connection to the earth are called grounding; it can also be referred to as grounding for electrical equipment, towers or overvoltage protection devices The wire is connected to the ground through metal conductors buried in the ground and in direct contact with the ground. The grounding part of the power system is generally a neutral point, or it can be a point on the phase line. The grounding part of the electrical equipment is a normally uncharged metal conductor, usually a metal shell. Here are the basic requirements for grounding.

 grounding

Why is the metal housing of the electrical equipment grounded?

The metal shell of the equipment is insulated from the live parts. The outer shell will not be charged, but if the inner insulator of the appliance is aged or damaged, the electricity may be transmitted to the metal shell. If the shell is not grounded, people will get an electric shock if they touch it. If the metal shell is grounded, current will flow into the earth through the ground wire, and people will not get an electric shock if they come into contact with the charged metal shell. Grounding is to use a thicker wire (preferably copper wire, aluminum wire is easy to be eroded or broken, generally can not be used as a ground wire), one end of it is connected to the electrical shell, and the other is buried underground A certain depth, and there is a certain length of angle, usually this connection is also called ground. The metal housing of the protective earthing device, the structure of the power distribution device, and the wiring pole tower, etc., which may be energized due to insulation damage, are grounded to prevent the danger of personal and equipment safety.

electromagnetic leakage protectors

First, the shell of the electrical equipment must be grounded, and its grounding generally has the following requirements:

1. The metal enclosure of the protected electrical equipment should be grounded separately.

2. The grounding of the metal casing of the electrical equipment of the protected electric single girder crane shall be separated from the grounding of the neutral point of the power supply.

Second, when the above requirements cannot be met and a common grounding method must be adopted, the following requirements shall be met:

1. When the electric single girder crane adopts the electromagnetic leakage protector, the enclosure of the protected electrical equipment can be connected to the protective earth (PE line) or the protection neutral line (PFN line). In this case, the automatic switch may not be checked, but the dynamic stability and thermal stability of the leakage protector (zero sequence transformer) must be checked.

2. When an electronic leakage protector is used, the metal housing of the protected electrical equipment can also be connected to the protective earth. In this case, in addition to checking the dynamic stability and thermal stability of the zero-sequence transformer, it is also necessary to check whether the auxiliary power supply voltage of the leakage protector is within the allowable voltage range when a single-phase grounding occurs. Ensure that the leakage protector can operate reliably.

electronic leakage protector

3, grounding resistance should be able to ensure reliable operation of leakage protection.

4. When the electric single girder crane power distribution system adopts the leakage protection grade protection, in order to make the protection devices at all levels selectively act, the breaking time of each level shall be different.


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