1. The role of the ground wire:
1. Protect personal safety: The role of the grounding wire is to protect personal safety. When static electricity discharges, a large amount of charge is generated, which can easily cause great harm to the electrical appliance itself and the human body. The grounding wire can avoid being damaged by the charge. The grounding wire has an important role in lightning protection. The protective effect can effectively extend the service life of electrical equipment. When electrical equipment leaks or is inductively charged, current can be quickly poured into the earth through the grounding wire so that the equipment shell is no longer charged, thus ensuring the safety of personnel and equipment.
Lightning protection: During thunderstorms, many tall buildings are in danger of being struck by lightning. However, after lightning protection measures are taken, the current can flow into the underground buildings along the grounding wire and remain intact.
Introduction: In electrical appliances, the ground wire is a line connected to the shell of electrical equipment and other parts to promptly conduct out unsafe charges or leakage currents generated due to various reasons. (1) Function of high-voltage grounding wire: High-voltage grounding wire is used in line and substation construction to prevent electrostatic induction from nearby charged objects and ensure safety when electric shock occurs or when the switch is accidentally closed. (2) High-voltage ground wire structure: The portable high-voltage ground wire consists of an insulated operating rod, wire clamp, short-circuit line, ground wire, ground terminal, bus clamp, and ground clamp. (3) High-voltage ground wire manufacturing process: Excellent manufacturing process - the wire clamp and grounding clamp are made of high-quality aluminum alloy die-casting; the operating rod is made of epoxy resin colored tube, with good insulation performance, high strength, light weight, bright color and beautiful appearance. Smooth; the grounding soft copper wire is made of multiple strands of high-quality soft copper wires and is covered with a soft, high-temperature-resistant transparent insulating sheath, which can prevent wear and tear on the grounding copper wire during use. The copper wire meets the fatigue test requirements. Ensure the safety of workers during operation. (4) Grounding wire specifications: According to ministry regulations, the grounding wire must be made of bare copper soft wire of 25mm 2 or more.
The basic components of the grounding method:
The components of the grounding method can be divided into two parts: electrical equipment and power distribution systems.
1. Grounded parts of electrical equipment
(1) Ground body: A conductor or a group of conductors that is in close contact with the earth and forms an electrical connection with the earth.
(2) Exposed conductive parts: conductive parts that can be touched by electrical equipment. It is not energized under normal circumstances, but may be energized during a fault. It is usually the metal casing of electrical equipment.
(3) Main grounding terminal board: a combination of various grounding (such as working grounding, protective grounding) terminals and equipotential bonding wire terminals in a building or part of a building. If arranged in a row, it is called the main ground terminal block.
(4) Protective wire (PE): A conductor that electrically connects any part of the above-mentioned exposed conductive parts, the main grounding terminal board, the grounding body, and the power supply grounding point (or artificial grounding point). A conductor connecting multiple exposed conductive parts is called a protective trunk.
(5) Ground wire: Connect the main ground terminal board or the exposed conductive part directly to the protective wire of the ground body. A ground wire connecting multiple ground terminal boards is called a ground trunk.
(6) Equipotential connection: refers to an electrical connection in which the potentials of each exposed conductive part and the conductive part outside the device are substantially equal.
Grounded portion of the power distribution system
(1) Phase line (L). Conductors that carry electrical energy are not normally grounded.
(2) Neutral wire (N). A conductor connected to the neutral point of the system and capable of transmitting electrical energy.
(3) Protect the neutral line (PEN). A conductor that functions as both a protective line and a neutral line.
(4) Power ground point. Ground the power supply at a point where it can be grounded (usually the neutral point)
Classification of grounding: The grounding method of my country's power distribution system has been stipulated by IEC. Its classification is still based on the grounding combination of the power distribution system and electrical equipment, and is generally divided into TN, TT, IT systems, etc. The meaning of the above letters: the first letter indicates the relationship between the power supply ground point and the ground. Among them, T means direct grounding; I means not grounded or grounded through impedance. The second letter indicates the relationship between the exposed conductive parts of the electrical equipment and earth. Among them, T means a separate direct grounding that is not connected to the power supply grounding point; N means it is directly connected to the power supply system grounding point or to a conductor drawn from this point.
Depending on whether the neutral line and the protection line are merged, the TN system is divided into TN-C, TN-S and TN-C-S systems. TN-C system: The protection line and neutral line are combined into a PEN line. TN-S system: The protective line and the neutral line are separated. TN-C-S system: The protection line and neutral line in a section near the power supply side are combined into a PEN line, and are divided into protection line and neutral line from a certain point onwards.
Resistor requirements:
The requirements for the resistance of high-voltage short-circuit grounding wires to ground determine the quality of the grounding wire. Generally, according to the technical regulations of the power industry DL-T879-2004, the resistance of each cross-sectional area of the grounding wire to ground shall not be greater than the following values:
Measure the DC resistance between the terminal lugs. For various cross-sections of 16mm2, 25mm2, 35mm2, 50mm2, 70mm2, 95mm2, and 120mm2, the average resistance value per meter should be less than 1.24mΩ, 0.79mΩ, 0.56mΩ, 0.40mΩ, and 0.28mΩ respectively. ,0.21mΩ,0.16mΩ
Technical parameters: (1) 10KV high-voltage grounding wire Insulated rod length: 700 mm Handshake length: 300 mm Metal joint length: 50 mm Number of sections: 1 Rod diameter: 30mm Total length (excluding wire clamp): 1050 mm
(2) 35KV grounding wire Nominal cross-section: 25mm2 Total number of wires: 810 Average diameter (mm): 0.2mm Calculated cross-section: (mm2): 25.43 Metal joint length: 50 mm Number of sections: 1 Rod diameter: 30mm
(3) 110KV high-voltage grounding wire Nominal cross-section: 35mm2 Total number of wires: 1136 Average diameter (mm): 0.2mm Calculated cross-section: (mm2): 35.67 Insulation rod length: 1360 mm Handshake length: 700 mm Metal joint length : 140 mm Number of sections: 2 Rod diameter: 30mm Total length (excluding wire clamp): 2200 mm
Instructions for use: (1) When hanging the ground wire: connect the ground clamp first, then the electric clamp; when removing the ground wire, you must first remove the electric clamp and then the ground clamp according to the procedure.
(2) Installation: Fix the double-eye copper nose on the grounding soft copper wire at the corresponding position of the power clamp on the ground rod (the power clamp has fixed and movable types), and connect the single-eye copper nose on the ground wire. Fix it on the ground clip or ground pin to form a complete set of ground wires.
(3) Verify whether the voltage level of the ground rod is consistent with the voltage level of the operating equipment.
(4) Grounding soft copper wires are available in split-phase and combined types, and grounding rods are available in flat-mouth and double-hook type clamps.
Use and maintenance: Before using the portable short-circuit grounding wire, you should first check the power to confirm that there is a power outage, and then proceed after confirming that there is no voltage on the equipment. First connect the grounding clamp to the grounding grid or flat iron, and then use a grounding rod to tighten the wire ends to the equipment wires. When removing the short-circuited ground wire, the sequence is exactly the reverse of the above. The distance between the installed short-circuit ground wire and the live equipment, taking into account the influence of the ground wire swing, should be no less than the value newly specified in the "Electrical Safety Work Regulations". It is strictly prohibited to use a wire clamp instead of winding to short-circuit the ground. If there is a grounding point at the suspension point, a grounding clip or a special copper rod should be used for the grounding connection; if there is no fixed grounding point available, a temporary grounding point can be used, and the grounding electrode should be buried underground to a depth of not less than 0.6m. Portable short-circuit ground wires should be kept properly. Before each use, you should carefully check whether it is intact, the soft copper wire is not exposed, and the nut is not loose, otherwise it must not be used. The inspection cycle of the portable short-circuit grounding wire is once every five years, and the inspection items are the same as the factory inspection. After a portable short-circuit grounding wire that has passed the test is subjected to a short-circuit, it should be judged based on the size of the short-circuit current and appearance inspection, and generally should be scrapped.