What are the differences between TN-C, TN-S, and TN-C-S? Advantages and disadvantages?

TN-C: the former Soviet Union model. Advantage: saves one wire (low investment). Disadvantages. There is no distinction between neutral and ground; the ground wire carries voltage (in the case of three-phase imbalance). TN-S is currently the standard approach, as it offers the advantage of a complete separation between the safe neutral and ground wires. There is no current in the PE wire. Voltage. . Disadvantages: Multiple wires (high initial investment). TN-C-S is simply a TN-C system. . Perform additional grounding on some important devices, or those that are prone to electrical leakage. It should be noted, however, that once additional grounding is done, all devices following those devices must operate in the TN-S mode; otherwise, wiring faults may spread and become more serious. Advantages: it facilitates the renovation of old systems, and the investment required is not high. Disadvantages: Achieving the TN-S configuration with complete repeated grounding is easy in theory, but it requires time and space. Deviations may occur after personnel changes! ~! Currently, I generally use the TN-S system for design. . After these several modes, there is another important new topic, namely equipotentiality. . (Overall equipotential, local equipotential) This post was last edited by ZJYSSF on 2009-3-18 at 18:54]

1. Technical measures for safe electricity use: (1) Protective grounding refers to establishing a reliable electrical connection between the non-live metal casing of electrical equipment and the grounding electrode. Its function is that when the metal casing of an electrical device is charged, if a person touches this casing, since the resistance of the human body is much higher than that of the grounding conductor, most of the current flows into the ground through the grounding conductor, while only a small amount of current flows through the human body. At this time, by properly controlling the grounding resistance (generally not exceeding 4Ω), electric shock accidents can be reduced. However, in TT power supply systems, the voltage on the equipment enclosure of devices using this protection method remains quite dangerous to humans. Therefore, this protection method is only applicable to construction sites with TT power supply systems, where the resistance of the protective grounding is required to be no greater than 4Ω. (2) Protective zero connection: In low-voltage power systems where the power supply neutral point is directly grounded, connecting the metal casing of electrical equipment directly to the neutral wire or a dedicated neutral wire in the power supply system is known as protective zero connection. Its function is to ensure that when the metal casing of electrical equipment becomes charged, the short-circuit current forms a closed circuit through the neutral wire, resulting in a single-phase short-circuit fault. Since the impedance of the neutral wire is very low, the short-circuit current is high, usually several times or even dozens of times the rated current. Such a severe single-phase short-circuit causes the protection device to act quickly and accurately, cutting off the power supply in order to ensure personal safety. Its power supply system is a zero-connected protection system, namely the TN system. Whether the protective neutral is separated from the working neutral allows the TN power supply systems to be classified into three types: TN-C, TN-S, and TN-C-S. 1) TN-C power supply system. Its working neutral wire also serves as the earth connection protection wire. This power supply system is what is commonly referred to as the three-phase four-wire system. However, when the three-phase load is unbalanced, there is an unbalanced current in the neutral wire; as a result, the metal casing of the electrical equipment connected to the protective wire has a certain potential. If the neutral wire is broken, the casing of a leakage-proTECTED device connected to ground becomes charged. Therefore, this power supply system has certain drawbacks. 2) TN-S power supply system. It is a power supply system that strictly separates the working neutral wire N from the dedicated protection wire Pe at the power source, also known as the three-phase five-wire system. Its advantage is that there is no current in the dedicated protection wire, which is specifically used to carry fault currents to ensure that the protective device operates. It should be specifically noted that the PE wire must not be disconnected. At the power supply terminal, the PE wire should be grounded repeatedly. 3) TN-C-S power supply system. At a construction site, if a transformer is shared with another entity, or if the neutral point of the transformer at the site is not connected to a PE wire – resulting in a three-phase four-wire power supply – and yet a dedicated protective PE wire is required at the site, then a separate PE wire can be drawn out by performing repeated grounding of the neutral wire in the main electrical panel at the site. Such a system is known as a TN-C-S power supply system. During construction, it should be noted that except at the main panel, the N wire and the PE wire must not be connected anywhere else. Switches and fuses must not be installed on the PE wire, nor should the ground be used as a PE wire. The PE wire must also not enter the leakage protector, as the operation of the leakage protector at the end of the circuit will cause the preceding leakage protectors to activate as well. Whether protective grounding or protective neutralizing is used, it must be noted that in the same system, it is not allowed to ground some equipment while neutralizing another. Because in the same system, if some devices are grounded while others are connected to the neutral wire, then when a grounded device experiences a shell leakage, the potential of the neutral wire will rise, causing the casings of all devices connected to the neutral wire to acquire a dangerous voltage.

TN-C: three-wire, four-conductor system; TN-S: three-wire, five-conductor system. It is more commonly used in mobile devices. TN-C-S: the neutral wire is grounded multiple times; it is more frequently used in construction projects