TN-C系统、TN-S系统、TN-C-S系统Tn-csystem,tn-ssystem,tn-c-ssystem

1、最新资料推荐TN-C 系统、TN-S 系统、TN-C-S 系统(Tn-c system, tn-s system, tn-c-s system )TN-C 系统、TN-S 系统、TN-C-S 系统(Tn-c system, tn-s system, tn-c-s system) TN-C 系统、TN-S 系统、TN-C-S 系统(Tn-c system, tn-s system, tn-c-s system ) TN - C system, TN - S system, TN -C - S system According to the current national standard lo

2、w voltage distribution design specification (GB50054) definition, the low-voltage distribution system is divided into three kinds, namely TN, TT, IT three forms. Among them, the first capital letter T means that the neutral point of the power transformer is earthed directly; the I indicates unground

3、ed neutral grounding of the power transformer (or through high impedance grounding). The second capital letters, T, indicate that the enclosure of the electrical appliance is directly grounded, but is not connected to the grounding system of the power grid; the N indicates that the outer shell of th

4、e electrical equipment is connected to the neutral line of the system. TN system: the neutral grounding of the power transformer, the exposed part of the equipment is connected with the neutral line. TT system: neutral grounding of power transformer, protective earthing of electric equipment1 / 10 e

5、nclosure. IT system: ungrounded neutral power transformer (or through high impedance grounding), and electrical equipment, enclosures, electrical equipment enclosures using protective grounding. TN system The neutral point of power transformer power system grounding, according to the different modes

6、 of electrical equipment exposed conductive part connected to the system and can be divided into three categories: TN - C - S system, TN system, TN - C - S system. The following are described separately. Its characteristic is: the power transformer neutral point ground, protects the zero line (PE) a

7、nd works the zero line (N) to share. (1) it is the neutral line using neutral grounding system (zero line) as a return conductor of fault current, when the electrical equipment line touch shell, the fault current through the zero line back to the point, because of the short circuit current, so it ca

8、n be used to cut off the power supply overcurrent protection device. TN - C system adopts zero sequence current protection; (2) TN -C system is suitable for three-phase load balance occasions, if the three-phase unbalanced load, the PENline has unbalanced current and harmonic current caused by load

9、of some equipment will also inject PEN, and neutral N charged, and most likely higher than 50V, which not only makes the equipment chassis最新资料推荐charged and to persons caused by unsafe, but also unable toobtain a stable reference potential; (3) the TN - C systemshould repeatedly ground the PEN line,

10、which can effectivelyreduce the zero - to - ground voltage when the zero - pointequipment is contacted with the case. As you can see, thefollowing defects exist in the TN-C system: (1) whenthethree-phase load is unbalanced, the unbalanced current appears on the zero line, and the zero line presents

11、voltage to the ground. When the three-phase load is seriously unbalanced, touching the zero line maylead to an electric shock accident. (2) the zero line of the leakage protective switch can only be used as the working zero line, and can not be used as the protective zero line of the electric equipm

12、ent, which is determined by the working principle of the leakage switch. (3) butt diode leakage protection switch of single-phase electrical equipment, such as for the protection of the metalshell in TN-C system is connected with the zero line,thecircuitof the zero line is not allowed to meet in fro

13、nt of theleakage protection switch PENline, but in use, prone to error connection. (4) the connecting line of the repeating earthing device is strictly prohibited to be connected with the work zero3 / 10 line through the leakage switch. The TN-S power supply system separates the work zero line from

14、the protective zero line, thus overcoming the defects of the TN-C power supply system, so the TN-C system is no longer used in the construction site. The neutral line (N) of the whole system is separated from the protective line (PE). (1) when the wire of the electricalequipment meets the shell, it

15、is directly short circuited, and the overcurrent protector can be used to cut off the power supply; (2) when the N line is disconnected, such as the unbalanced three-phase load, the neutral point potential increases, but the case has no potential and the PE line has no potential; (3)TN S system shou

16、ld be repeated grounding atthe end of PE line to reduce the risk of PEline disconnection.(4) TN - S system is suitable for industrial enterprises andlarge civil buildings. At present, a single transformer power supply or substation is used, and the construction site near the construction site basica

17、lly adopts the TN - S system, which is in line with the gradual leakage protection, Indeed, it has played a role in ensuring the safety of construction power consumption, but the TN- S system must pay attention to several problems (1) the protection of the zero line is absolutely not allowed to be d

18、isconnected. Otherwise in the grounding最新资料推荐equipment shell or touch live parts of the leakage, would not constitute a single-phase circuit, the power supply will not be automatically cut off, will have two consequences: one is that the zero loss of security protection equipment; two is to makethe

19、other good grounding equipment live shell, electrical equipment shell caused by electrification the scope of theelectric shock caused terrible threat. Therefore, in the JGJ46-88 construction site temporary power safety technical specifications stipulates that special protective lines must be repeate

20、d at the end of the ground. (2) the electrical equipment in the same power system shall not be allowed to be partially grounded or partly earthed. Otherwise, when the protective grounding equipment leakage occurs, the neutral grounding wire potential will rise, resulting in all protective devices co

21、nnected with zero charged live. (3) protect the material and connection requirements of the zero PE line: protect the cross section of the zero line to be not less thanthe cross section of the working zero line, and use the Yellow / green double color line. The protective zero line connected to the

22、electrical equipment shall be an insulated multi stranded copper wire with a cross-section of not less than5 / 102.5mm2. The protection of the zero line connected with the electrical equipment should be used copper nose reliable connection, not using articulated; electric equipment wiring column sha

23、ll be galvanized or coated anticorrosive grease, protective zero line should be connected through the terminal board in the distribution box, without joint in other places.TN - C - S system: it consists of two grounding systems. The first part is TN - C system, the second part is TN - S system, and

24、its interface is the connection point between N line and PE line. (1) when the electrical equipment has single phase shell collision, it is the sameas TN - S system; (2) when the N line is disconnected, the fault is the same as that of theTN - S system; (3) in TN - C - S system, PEN should be ground

25、 repeatedly, and Nline should not repeat ground. The equipment shell connected by PEline will not be electrified during normal operation, so the TN - C - S system improves the safety of operators and equipment. Generally, the construction site adopts the TN - C - S system when the substation is far

26、away from the field or there is no construction special transformer. TT power supply system, The neutral point of the power supply is directly grounded, and the exposed conductive part of the electrical equipment is connected to the grounding electrode最新资料推荐by the PE wire (the grounding electrode is

27、 connected with the neutral point without electrical contact) When using this system protection, when a device leakage fault, the equipment metal shell with a larger fault voltage, and the current is smaller, is not conducive to the protection of the action ofthe switch, it is harmful to people and

28、equipment. In order to eliminate the defects of T system and improve the reliability of power supply safety, according to the principle of shunt resistance, the technical innovation of TT system is improved. The content of technological innovation is: not less than zero section of the green / yellow

29、 color line (PT line), 4-5 grounding resistance protection parallel distribution box, distribution box, the main mechanical equipment under buried ground to ground protection, with green / yellow color lineconnecting metal electrical equipment shell. It has the following advantages: 1) the single-ph

30、ase earth fault point, the earth voltage is low, the fault current is larger, so that the leakage protector fast action, cut off the power supply, is conducive to prevent electric shock accident. 2) the PTline is not connected with the neutral line, line clear, intuitive, not take the wrong line of

31、accidents; several construction7 / 10 units and the construction site can be divided and set the unit of the PT line, is conducive to the safe use of electricity and save the amount of wire management. 3) without each electrical equipment under repeated burying ground, burying ground can save costs,

32、 but also conducive to improve the quality of grounding and grounding resistance less than 10 ohm, electrical safety protection more reliable TT system is widely used in foreign countries, and it is limited to local electronic equipment in the local docking area. At present, this system is not used

33、in the construction site. But if the utility transformer is used and other users use the TT system, the system shall be adopted at the construction site. The live part of a power system has no direct connection (or resistance to grounding) between the earth and the earth, The exposed part of the rec

34、eiving device is connected to the ground directly through the protective wire. This system is mainly used in the high voltage system of 10KVand 35KVand somelow voltage power supply system in mine and underground. It is not suitable for application in the construction field, so it is no longer analyz

35、ed here. The new construction safety inspection standard (JGJ59-99) issued by the Ministry of construction stipulates that the TN-S neutral grounding protection system最新资料推荐must be adopted in the power system of the special neutral point grounding directly on the construction site. Therefore, TN-S z

36、ero connection protection system has been widely used in the construction site, but if the PE line breaks or electrical equipment does not do the electrical connections, repeat grounding resistance is not up to the security requirements, also electric shock accident, in order to improve the safetyof TN-S ground zero protection system, is proposed in this paper equipotential connection concept. The so-called equipotential bonding, the exposed con