Explosion-proof Electrical Equipment Grounding Protection Function and Grounding Methods

Understanding explosion-proof electrical equipment

Grounding is used to prevent electric shock or protect equipment safety, by connecting the metal chassis or outer casing of explosion proof vfd electrical equipment to the grounding wire; using the earth as the grounding wire for current circuits. In power systems, the neutral point, outer casing, or bracket of equipment and electrical equipment are electrically connected to the grounding device through a wire, which is called grounding. For grounding protection, we generally only know that it can prevent people from getting an electric shock. In fact, in addition to this function, grounding can also prevent equipment and line damage, fire, lightning, electrostatic damage, and ensure the normal operation of electrical equipment.

Grounding methods of explosion-proof electrical equipment

The common grounding methods include repeated grounding, protected grounding, working grounding, lightning protection grounding, shield grounding, and anti-static grounding.

• Repeated Grounding: The repeated grounding of explosion-proof electrical equipment refers to one or more places where the zero line is connected to the grounding device through a metal wire in a system directly grounded at the neutral point. When installing in a low-voltage three-phase four-wire system directly grounded at the neutral point, the construction unit should ground the zero line backbone and terminal of the distribution line, and ground the zero line backbone every 1 kilometer. For distribution lines more than 50 meters away from the grounding point, the zero line of users should still be repeatedly grounded, and the repeated grounding resistance should not be greater than 10 ohms.

• Protected Grounding: Generally, the metal casing and metal bracket of explosion-proof electrical equipment are connected to the earth, which is called protected grounding. Protected grounding is mainly used for power supply systems where the neutral point is not grounded. If protective grounding measures are not taken, when a person's body comes into contact with a live shell, due to the capacitive coupling between the transmission line and the earth, the person's body will form a circuit, resulting in an electric shock accident. If protective grounding measures are taken for electrical equipment, when a person's body comes into contact with a live shell, the body's resistance is in parallel with the protective grounding device. Because the grounding resistance is smaller than the body resistance, it can be assumed that the current through the body is very small, and the electric shock accident is avoided.

• Lightning Protection Grounding: Explosion-proof electrical equipment lightning protection grounding is a part of lightning protection measures, and its function is to lead lightning current into the ground. Lightning arresters are mainly used for building and electrical transmission substation equipment lightning protection. One end of the arrester is connected to the protected equipment, and the other end is connected to the grounding device. In the case of a direct lightning strike, the lightning arrester leads the lightning to itself, and the lightning current enters the ground through its descending line and grounding device. In addition, for the electrostatic induction effect caused by lightning, in order to prevent indirect damage such as building fires or electric shocks, it is usually necessary to ground metal equipment, metal pipelines, and reinforced structures in buildings.