General management regulations on grounding and zero connection of electrical equipment: (1) grounding: some conductive parts of electrical devices and facilities in power systems or buildings are connected to grounding electrodes through grounding wires.
(2) working grounding (system grounding): In the electrical devices of the power system, grounding is provided for operation (such as direct neutral grounding or? Grounding through other equipment, etc. ).
(3) Protective grounding: metal shell of electrical device, frame of power distribution device, line tower, etc. It may be electrified due to insulation damage to prevent it from endangering personal and equipment safety.
(4) Lightning protection grounding: grounding of lightning protection devices (lightning rods, lightning wires, lightning arresters, etc.). ) release lightning current to the earth.
(5) Anti-static grounding: grounding to prevent the dangerous effect of static electricity on combustible oil products, natural gas storage tanks and pipelines.
(6) Grounding electrode (grounding body): The metal conductor buried in the ground and in direct contact with the earth is called grounding electrode. Grounding body is divided into natural grounding body and artificial grounding body. All kinds of metal components, metal well pipes, foundations of reinforced concrete buildings, metal pipes and equipment that are in direct contact with the earth and used as grounding electrodes are called natural grounding electrodes. (Pipes containing flammable liquids and flammable or explosive gases cannot be used as natural grounding bodies). The artificial grounding body is usually driven vertically into the soil by steel pipe angle steel, and can also be made of flat steel or round steel buried in the soil.
(7) Grounding wire: the metal conductive part used to connect the grounding terminal and grounding electrode of electrical devices and facilities.
(8) Grounding device: the sum of grounding wire and grounding electrode.
(9) Grounding grid: a large horizontal grid grounding device composed of vertical and horizontal grounding electrodes, which is used in power plants and substations and has the functions of discharging current and equalizing voltage.
(10) Centralized grounding device: an additional grounding device laid to enhance the scattering effect of lightning current and reduce the ground potential. Generally, 3-5 vertical grounding electrodes are laid. In areas with high soil resistivity, lay 3-5 radial horizontal grounding electrodes.
(1 1) grounding resistance: the sum of grounding resistances of grounding electrodes or natural grounding electrodes is called grounding resistance of grounding device. The grounding resistance value is equal to the ratio of the voltage of the grounding device to the ground and the current flowing into the ground through the grounding electrode. The resistance obtained by power frequency alternating current flowing into the earth through the grounding electrode is called power frequency grounding resistance; The grounding resistance obtained by impulse current flowing into the earth through the grounding electrode is called impulse grounding resistance.
(12) Ground potential of grounding device: potential difference between grounding device and ground zero potential point when current flows to the ground through the grounding electrode of grounding device.
(13) Contact potential difference: When grounding short-circuit (fault) current flows through the grounding device, a distributed potential is formed on the surface of the earth. The potential difference between two points, namely, the horizontal distance of 0.8m from the ground and the vertical distance of 1.8m from the equipment shell, frame or wall, is called contact potential difference; the maximum potential difference between the center of the grounding grid and the grounding pole of the grounding grid is called maximum contact potential difference.
(14) Step potential difference: When short-circuit (fault) current flows through the grounding device, the potential difference between two points with a horizontal distance of 0.8m on the ground is called step potential difference. The potential difference of the grounding electrode at the edge of the grounding grid at a horizontal distance of 0.8m on the ground outside the grounding grid is called the maximum step potential difference.
(15) Exposed conductive parts: conductive parts that are easily accessible in electrical equipment, which have no voltage at ordinary times, but can bring voltage in case of failure.
(16) conductive parts outside the equipment: conductive parts that do not belong to electrical equipment.
(17) electrical device: a combination of related electrical devices used for a specific purpose, which are matched with each other in characteristics.
(18) "Zero" means neutral conductor (neutral line): a conductor connected to the neutral point of low-voltage system and capable of transmitting electric energy.
(19) "Grounding" refers to the protective conductor: the exposed conductive part (i.e. the metal shell; Grounding terminal or main grounding body; Power grounding point or artificial neutral point.
(20) Contact voltage: When the insulation of electrical equipment is damaged, the voltage between parts that can be touched by human body at the same time.