Views:67 Author:Site Editor Publish Time: 2019-07-23 Origin:Site
Grounding device is also called grounding integrated device: a device that electrically connects electrical equipment or other objects to the ground. The grounding device consists of grounding pole, grounding busbar (indoor, outdoor), grounding down conductor (grounding jumper), and frame grounding. It is used to achieve the purpose of connecting the electrical system to the earth. A metal object that is in direct contact with the earth to make an electrical connection is called ground electrode. It can be an artificial ground or a natural ground.
This grounding pole can be assigned some electrical functions, such as grounding system, protective grounding or signal grounding. The grounding busbar is the reference potential point of the building's electrical installation, which connects the part of the electrical installation that needs to be grounded to the grounding pole. It also have another purpose of interconnecting the equipotential bonding lines within the electrical device to achieve a total equipotential bonding between the large conductive portions of a building. The connection line between the grounding electrode and the grounding busbar is called grounding lead.
The grounding device is composed of a grounding body (round steel, angle steel, flat steel, steel pipe, etc.) buried in the earth and grounding wire for connection.
According to the purpose of grounding, the grounding of electrical equipment can be divided into: working grounding, lightning protection grounding, protective grounding, and instrument control grounding.
It is a grounding required to ensure the normal operation of the power system. For example, the neutral point of the transformer in the neutral point direct grounding system is used to stabilize the grid to ground potential, so that the ground insulation can be reduced.
It is a grounding set for lightning protection needs. For example, the grounding of the lightning rod and the arrester is designed to allow lightning current to smoothly enter the earth to help reduce the lightning overvoltage, which is also called overvoltage protection grounding.
Also called safety grounding, it is grounding for personal safety. That is, the electrical equipment casing must be grounded to prevent the casing from being charged and endangering personal safety.
Instrument control grounding, which covers power control system, data acquisition system, computer monitoring system, transistor or microcomputer type relay protection system and telecontrol communication system, etc, the function is to stabilize potential and prevent interference. It's also known as electronic system grounding.
Ground resistance is the resistance encountered when current flows through the grounding body into the ground and spreads around. The earth has a certain resistivity, and if there is a current flowing, the earth has different potentials everywhere. After the current is injected into the earth through the grounding body, it spreads in all directions in the form of a current field. The farther away from the grounding point, the larger the hemispherical diffusing area, the smaller the current density in the ground, so it can be considered at a distance (about 15~20m away), the resistance of the unit diffusion distance and the current density in the ground are close to zero, and the potential at this point is zero potential.