Views:88 Author:Site Editor Publish Time: 2019-08-14 Origin:Site
The function of grounding device is to prevent personal injury from electric shocks, damage on equipment and wiring, to prevent fires and to prevent lightning strikes, to prevent electrostatic damage and to ensure successful operation of the power system.
Grounding devicw is an electrical safety measure adopted to ensure the normal operation and personal safety of electrical equipment. It is realized by connecting metal wires to grounding devices. The most common grounding methods include protective grounding, working grounding, lightning protection grounding, shielding grounding, and anti-static grounding. The grounding device introduces leakage current, static charge and lightning current generated on electrical equipment and other production equipment into the ground, thereby to avoid personal electric shock and fire, explosion and other accidents.
Grounding protects the human body by making a good metal connection between the metal parts of the electrical equipment that are not normally charged and the grounding electrode.
As for electrical equipment with grounding devices, when the insulation is damaged and the enclosure is energized, the ground current will flow through both the grounding pole and the human body. The value of the current flowing through each path will be inversely proportional to the magnitude of its resistance. The smaller the grounding resistance, the smaller the current flowing through the body. When the grounding resistance is extremely small, the current flowing through the human body approaches zero, thus, the human body avoids the risk of electric shock. In any case, ensure that the grounding resistance is not greater than the grounding resistance specified in the design or procedure.
The grounding of the power system is generally grounded at the neutral point, so the potential between the neutral point and the ground is close to zero. When the phase line is touched or grounded, the other two relative ground voltages will rise multiply of the phase voltage in the neutral point insulation system; in the neutral point grounded system, it is close to the phase voltage. Due to the grounding line of the neutral point, the reliability of relay protection can be guaranteed. The DC power supply in the communication system is generally grounded with a positive pole to prevent noise from entering and ensuring normal operation of the communication equipment.
1. The buried depth of the top surface of the grounding body should meet the design requirements. When there is no regulation, it should not be less than 0.6m.
2. The space of vertical grounding bodies should not be less than 2 times their length. The space of the horizontal grounding body should meet the design requirements. When there is no design rule, it should not be less than 5m.
3. the grounding wire should prevent mechanical damage and chemical corrosion;
4. The grounding trunk should be connected to the grounding grid at two or more different points.
5. The grounding electrical device should be connected to the grounding mains with a separate grounding wire.
6. The soil in the backfill after the grounding body is laid should not contain stones and construction waste; the soil taken outside should not be corrosive; it should be layered when backfilling.
7. The connection of the grounding body (wire) should be welded, and the welding must be firm and free of solder joints. Connect to the grounding wire of the electrical equipment and connect with galvanized bolts.
8. The grounding body (wire) welding shall be lap welding.