Electrical equipment grounding meet the requirement of zero

by:Mings     2020-04-20
1. General requirements (1) in order to guarantee the personal safety, all electrical equipment shall be installed grounding device, and the electrical equipment enclosure grounding and zero. (2) a variety of electrical equipment grounding protection and grounding and overvoltage protection work, usually can use a general grounding device, the grounding resistance shall meet the provisions of the minimum standard of grounding resistance. (3) under the voltage of 1 kv neutral directly grounded electrical devices, electrical equipment enclosure unless otherwise specified, must be connected with the electrical equipment grounded neutral metal, to ensure that the can quickly and reliably when the short circuit will automatically disconnect point of failure. Artificial grounding body (4) electrical equipment, such as pipe, flat steel, round steel and so on should be as far as possible make electrical equipment near the location of uniform voltage distribution, large grounding short-circuit current electrical equipment must be installed ring body, and equipped with equalizing zone. 2. Together with zero of separate grounding requires (1) in the same voltage and electrical connection systems, all electrical equipment should use common ground, the grounding device electrical connection between the two, are not allowed to separate grounding. (2) by the same generator, transformer, or the same section of the bus power supply line should be taken to the same ground work. (3) in the same workshop, 1 kv and below 1 kv electricity equipment should adopt common grounding, neutral point of work is not at the same time should also be common ground. (4) using uniform zero are in trouble, don't meet zero electrical equipment or line should be installed automatically disconnect power leakage protection or protection device of fault point. (5) the working grounding and protection of electric equipment should be separated from grounding, and maintain a certain prevent back a safe distance. 3. Repeat grounding requirements (1) in the neutral point grounding of low voltage line directly overhead lines, length of more than 200 m at the end of the overhead lines branch and branch, branch line at the end of the line every 1 km straight segment of the zero line should be repeated earthing. (2) total stem erect, high and low voltage lines in total stem erect section on both ends of the terminal bar, low voltage line of zero line should be repeated earthing. At this point, such as low-tension wire feeder derivation length more than 500 m in the branch zero line will repeat grounding. (3) a special thread for zero line or cable metal sheath is used as the zero line of low voltage cable line will repeat grounding, the requirement is the same as the overhead lines. (4) and the potential for such as reducing the contact voltage, workshop in the metal structure and underground pipelines shall be connect with the ground wire of annular repeat grounding, but the whole workshop shall also have the necessary concentration repeat grounding device. (5) line introduced in workshop and the first side of a large building power distribution unit ( Into the door) Should repeat grounding. 6. The use of metal pipe matching, after the tube is connected to the protective zero line do repeat grounding; Using plastic piping, separately equipped to protect the zero line and make repeat grounding. 7 when work grounding resistance less than 4 Ω, every repeat grounding resistance shall not exceed 10 Ω; In power distribution transformer capacity of 100 kva and below, work on the low voltage side of transformer neutral point grounding resistance allows no more than 10 Ω occasions, every repeat grounding resistance allows of no more than 30 Ω, but should not less than three. 4. Special equipment grounding requirements (1) portable electrical equipment should be adopted, for the special grounding conductor, shall not be used near the zero line is used as the ground, the zero line and the ground wire connected to ground net. through separately. (2) general industrial electronic equipment should have a separate grounding system, grounding resistance should no more than 10 Ω, grounding body and equipment should be not more than 5 m distance. (3) power supply of neutral point grounding system arc furnace equipment, the shell and the furnace shell shall be grounding, grounding resistance is not less than 4 Ω, ground wire for the section is not less than 16 mm copper stranded wire; Neutral zero power system of electric arc furnace equipment shell and the furnace shell should be taken to protect the zero. (4) in dc equipment, for often doesn't flow through the dc system, in the protective grounding and zero requirements same as communication equipment; In the dc equipment, special occasions, generally USES the neutral point insulation system, the requirement for protective earthing and communication are the same. A pole or neutral point grounding of the rectifier, the system zero should be used, or furnish grounding short circuit relay, to ensure that the equipment shell can be quickly removed when the ground fault. In order to reduce the leakage current of large electrolytic cell, generally don't use grounding method, and adopt the method of reinforced insulation.
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