Automated customs declaration checks

List of contents of this article:

• 1,Automated customs declaration checks What wiring method (power distribution system)? What are T, N and S?
• 2、 What are the advantages and disadvantages of direct grounding and non-direct grounding of neutral points in the power grid? In China's power system...

What wiring method (power distribution system)? What are T, N and S?

x0dx0aTN-S system x0dx0a TN-S grounding system is a grounding type that strictly separates the working zero line (N line) and the special protection zero line (PE line). As shown in Figure 2.

TN-mode power supply system, a protection system that connects the metal shell of electrical equipment to the working zero line, is called the zero protection system, which is represented by TN. The working zero line of the TN-C power supply system is also used as a zero protection line, which can be called a protection neutral line and can be represented by PEN.

TN-S system three-phase five-wire system, the transformer output three-phase five-wire system PE is grounded within the specified distance, and the household end is grounded nearby. Five-wire arrival electrical equipment.The device can be directly wired to the user and take the seat! The wires are divided into yellow, green, red, N light blue and PE yellow-green wires.

tn-s power supply system It is a power supply system that strictly separates the working zero line n and the special protection line pe, which is called the tn-s power supply system. As shown in Figure 1-4, the characteristics of the tn-s power supply system are as follows. ( 1) When the system is running normally, there is no current on the dedicated protection line, but there is an unbalanced current on the working zero line.

When the TN-S system is directly grounded at the neutral point of the power transformer on the power supply side, the exposed conductible part of the uncharged electrical equipment on the load side is protected through the zero-line grounding protection system. The power supply system is a system composed of a power supply system and a power transmission and distribution system that generates electricity and supplies and transmits it to electrical equipment.

Is the it system a protective zeroing system?

It system is wrong to protect the zeroing system. The IT system is to protect the grounding system, not the zeroing system. Grounding and zeroing are different. The IT system is not directly connected to the earth, and the exposed conductive part of the electrical device is connected to the grounding pole through the protective ground wire.

Answer: No, IT system (information technology system) is a broad concept that covers computer hardware, software, network and data storage, etc., and is used to process and manage information. Protecting the zeroing system is only a small part of the IT system.

IT system is a low-voltage power distribution system, and "protection zero connection system" is only a one-sided statement. Definition of IT system: a system in which the neutral point of the power supply is not grounded, and the exposed conductive part of the electrical equipment is directly grounded.The IT system can have a neutral line, but IEC does not recommend setting a neutral line.

[Answer]: A IT system is to protect the grounding system. Its safety principle is to limit the fault voltage within the safe range through low-resistance grounding. However, it should be noted that the leakage state has not disappeared due to the protection of grounding. Protective grounding is applicable to all kinds of ungrounded distribution grids, such as some 1 to 10 kV distribution grids, low-voltage distribution grids under coal mines, etc.

What is the wiring method (power distribution system)? What are T, N and S respectively??

1. Starting from the main switchgear (main distribution box) of the building power supply line, the TN-C grounding type is converted to the TN-S grounding system, that is, the second half of the system is the TN-S grounding system. From here to the end of the load, the PE line and N wire should be well insulated, and no more electricity is allowed. Gas connection, and repeat grounding of the PE line.

2. T--the exposed conductive part is directly electrically connected to the ground, which has nothing to do with any connection point of the power system; N--the exposed conductive part is directly electrically connected to the connection point of the power system (in the AC system, the contact point is usually the neutral point).

3. TN-mode power supply system is a protection system in which the metal shell of electrical equipment is connected to the working zero line, which is called the zero protection system, which is represented by TN. The working zero line of the TN-C power supply system is also used as a zero protection line, which can be called a protection neutral line and can be represented by PEN.

4. The power supply system is a system composed of a power supply system and a power transmission and distribution system that generates electrical energy and supplies and transmits it to electrical equipment. The power supply system can be roughly divided into three types: TN, IT and TT, among which the TN system is divided into three forms of expression: TN-C, TN-S and TN-C-S.

Is the it system a protection zero?

The it system is a protection zeroThe system is wrong. The IT system is a protective grounding system, not a protective zeroing system. Grounding and zeroing are different. The IT system is not directly connected to the earth, and the exposed conductive part of the electrical device is connected to the grounding pole through the protective ground wire.

Answer: No, IT system (information technology system) is a broad concept that covers computer hardware, software, network and data storage, etc., and is used to process and manage information. Protecting the zeroing system is only a small part of the IT system.

IT system is a low-voltage power distribution system, and "protection zero connection system" is only a one-sided statement. Definition of IT system: a system in which the neutral point of the power supply is not grounded, and the exposed conductive part of the electrical equipment is directly grounded. The IT system can have a neutral line, but IEC does not recommend setting a neutral line.

What are the advantages and disadvantages of direct grounding and non-direct grounding at neutral points in the power grid? In China's power system...

1. Advantages of the neutral point direct grounding system: When single-phase grounding occurs, the voltage of the other two intact grounds does not rise, so it can reduce the insulation cost; Disadvantages: single-phase When the ground is short-circuited, the short-circuit current is large, and the faulty part should be quickly removed, so that the reliability of the power supply is poor.

2. The system of direct grounding at the neutral point belongs to the large current grounding system. Generally, the current through the contact point is large, which may burn the electrical equipment. After a failure, the relay protection will act immediately to trip the switch and eliminate the failure.At present, most of the systems above 110kV in China are directly grounded at neutral points.

3. Advantages: For the neutral point grounding system of the power supply, if a single-phase grounding occurs, the voltage of the other two phases will not rise, which can reduce the insulation level of the whole system; in addition, single-phase grounding will produce a large short-circuit current Is, so that the protection device (relay, fuse, etc.) can move quickly and accurately. Work, improve the reliability of protection.

4. The neutral point is directly grounded. The neutral point is directly grounded, that is, the neutral point is directly connected to the earth. If a single-phase grounding occurs during the operation of the system, a single-phase short circuit will be formed, and the grounding current is large, causing the circuit breaker to trip and remove the fault. This kind of high-current grounding system is not equipped with an insulation monitoring device.

5. The operation mode of the neutral point in the power system: the neutral point is directly grounded.Disadvantages: The reliability of the power supply is low, and the grounding will short-circuit the contact point and the neutral point. The ground phase, or even the three phase, must be removed immediately. Advantages: relatively ungrounded, low insulation cost, more than 110kV, direct grounded, neutral point ungrounded, ungrounded.