Why is the enclosure grounded for large electrical equipment?

The two people upstairs said very well, but the shell of large electrical equipment is grounded, one is to protect the safety of personnel, and the other is to prevent static, usually in addition to equipment leakage, but also anti-static. The third is the foundation grounding, which is mainly to protect large electrical equipment against lightning strikes.

Grounding is a technology, the shell grounding is mainly for safety, to prevent the occurrence of shell events, this is the shell with AC220V electricity, if grounded, and the grounding resistance should be less than 4 ohms. If the human body comes into contact with the shell, which is the human body to the ground potential AC220V, if the device is also grounded at this time, 2 resistors (the human body resistance is much greater than the ground resistance) are connected in parallel, then the current flowing through the human body will be very small, less than 40mA. Protects the human body!

For safety, prevent leakage to prevent electricity from hurting people. As long as there is electricity leakage after connecting to the ground, it will be transmitted to the metal outer box for the first time, and the leakage protector will work after the outer box is connected to the ground, in fact, the general household appliances are also connected, such as computers, rice cookers, water dispensers, all three-plug, 220V household appliances are, and some household appliances are not connected to the ground wire in order to save wires.

Nice upstairs, I'll add one more point.

Large electrical equipment has high power, and the internal AC current can be coupled to the metal shell through the electromagnetic field to form an induced electromotive force, which makes the shell electrified. Therefore, large electrical equipment must have a well-grounded enclosure even if there is no leakage inside.

The grounding of the electrical equipment shell is protective grounding, which is to ensure the safety of people. This does not protect the device, the device has other protection.

Summary. The ground wire in the power box is generally connected to the ground grid (grounding pile), and the shell security grounding of other electrical equipment is best connected directly to the grounding network (grounding pile), and in the absence of conditions, it can also be connected to the ground wire of the power box.

The ground wire in the power box is generally connected to the ground grid (grounding pile), and the shell security shielding source of other electrical equipment is best connected directly to the grounding grid (grounding pile) macro liquid, and it is also possible to connect to the ground wire of the power box in the absence of conditions to bury early.

Yes, the grounding wire of the motor and the equipment shell can be connected in parallel, as long as the grounding wire of the equipment is reliably grounded, if it is a fake grounding wire, it cannot.

The exposed conductive parts of electrical equipment must be grounded, including but not limited to the exposed conductive parts listed below: (1) metal bases and shells of motors, transformers, electrical appliances, portable electrical appliances and mobile electrical appliances. (2) The metal box of the box-type substation, the shell of the generator neutral point cabinet, the shell of the generator outlet cabinet, and the closed bus shell.

3) The metal shell of the junction box, terminal box and expander of AC and DC power cables and the metal sheath of the cable, the metal trunking and cable tray of the steel pipe laying cable that can be touched and threaded; electrical equipment transmission devices; Exposed conductive parts of metal lighting fixtures. (4) Metal frames and bases of screens, cabinets, boxes and operating consoles for power distribution, control and protection, and metal shells of fully enclosed combined electrical; Metal and reinforced concrete frames for indoor and external power distribution installations, as well as metal fences and metal doors near live parts. (5) metal towers and reinforced concrete towers of overhead power lines; Exposed conductive parts and brackets of switchgear, capacitors, and other electrical devices installed under power line towers.

The metal shell of the equipment is insulated from the live part, and the shell will not be electrified, but if the internal insulator of the appliance is aged or damaged, the electricity may be transmitted to the metal shell, if the shell is not grounded, then the person will be electrocuted if it touches it, and if the metal shell is grounded, the current will flow into the earth through the ground wire, and the person will not be electrocuted when he touches the live metal shell. Grounding is to use a thicker wire (preferably copper wire, aluminum wire is easy to be corroded or broken, generally can not be used as a ground wire), one end of it is connected to the electrical shell, and the other end is connected to a certain depth buried in the ground, and has a certain length of angle steel, usually this connection wire is also called ground wire.

Summary. The metal casing and the internal wires form a capacitance, through which alternating current energy is "passed" to electrify the metal casing. Grounding is only a way for people to touch it without being dangerous, but there is still a sensation of electric shock.

The equipment shell is electrified, and the equipment shell is still live after the grounding wire is installed, what is the reason for this?

The metal casing and the internal wires form a capacitance, through which alternating current energy is "passed" to electrify the metal casing. Grounding is only a way for people to touch it without being dangerous, but there is still a sensation of electric shock.

When connecting electricity, it is necessary to distinguish between the zero wire and the ground wire, usually the ground wire is not electrified, if the grounding wire is electrified, it is very dangerous, what is the reason for the grounding wire to be electrified? What is the cause of the live grounding wireThis is because the metal shell is easy to form a capacitance with the wires inside the appliance, and the induced current is generated. In addition, the conductivity of the metal shell is relatively strong, if leakage occurs inside the appliance, the shell will be electrified, therefore, the wire must be connected to the shell to make it grounded, so that once the shell is live, it can be quickly connected to the ground through the ground wire.

The function of the ground wire is to protect the electrical appliances when they leak again, and the current flows to the ground to ensure the safety of electrical appliances and people.

What is the function of the grounding wire 1. Protect personal safety Because electrostatic discharge is easy to produce a large amount of charge, if the electrical equipment is not properly insulated, it is easy to cause great harm to the electricity itself and the human body. The role of the ground wire is to act as a wire between the high-voltage equipment and the ground, preventing us from being damaged by the charge. 2. In the past, in the case of thunder and rain, power poles and other equipment were often damaged by lightning strikes, and sometimes they could not be used for several days.

Therefore, the grounding wire can play a good role in lightning protection and effectively extend the service life of electrical equipment.

1. The grounding resistance of independent lightning protection should be less than or equal to 10 ohms.

2. The grounding resistance of independent safety protection should be less than or equal to 4 ohms.

3. The independent AC working grounding resistance should be less than or equal to 4 ohms.

4. The grounding resistance of the independent DC industrial roller pin should be less than or equal to 4 ohms.

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

6. The common grounding body (joint grounding) should not be greater than the grounding resistance of 1 ohm.

The shell of electrical equipment must be grounded, and there are generally the following requirements for its grounding:

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

2. The grounding of the metal shell of the electrical equipment of the protected electric single-beam crane should be separated from the grounding of the neutral point of the power supply.

Summary. Hello! Why should the metal enclosure of electrical equipment be grounded?

Because electrical appliances with metal shells generally have three-pin plugs, which correspondingly plug into three-pin sockets. Internally, due to the damage or loss of insulation properties of the insulating skin of the live wire, the shell is connected to the live wire and becomes electrified, and people will be electrocuted when they touch the shell. If the metal shell is to be grounded, the electricity carried by the shell will flow to the earth through the ground wire, and there is no danger for people to touch it.

Why should the metal enclosure of electrical equipment be grounded?

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Hello! Why should the metal enclosure of electrical equipment be grounded? Because the electrical appliances with metal flame shells are generally equipped with three-pin plugs, which are plugged into three-prong sockets.

Internally, due to the damage of the insulating skin of the live wire or the loss of the insulation performance of the fire wire, the shell is connected with the live wire and becomes electrified, and people will be electrocuted when they touch the shell. If the metal shell is to be grounded, the electricity carried by the shell will flow to the earth through the ground wire, and there is no danger for people to touch it.

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