Electrical professionals should be familiar with the neutral wire, neutral line N, and ground wire PE

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Live wires or phase wires are certainly well-known to most electrical workers, but when it comes to neutral wires, ground wires, and neutral lines, some people are not as familiar with them, and may even get them mixed up. So what exactly is the difference between the neutral wire, the zero wire, and the ground wire? Do you understand everything? I. Definitions and differences between the neutral wire, the zero wire, and the ground wire. Simply put, both the neutral wire and the zero wire are wires that originate from the neutral point of the power supply. The wire drawn out after the neutral point is grounded is called the neutral wire. The wire that results from the neutral point not being grounded is called the neutral wire. A wire that is connected to the ground is called a ground wire. Changhui Instruments yunrun.com.cn II. Differences between the neutral point and the zero point, as well as between the neutral wire and the zero wire 1. When the power supply side (transformer or generator) or the load side is connected in a star configuration, the common connection point at which the beginning (or end) of the three-phase coils are joined is called the neutral point, or simply the midpoint. The neutral point of a split power supply is divided into the neutral point of the power supply and the neutral point of the load. The wire leading from the neutral point is called the neutral wire, or simply the neutral line. If the neutral point is directly connected to the grounding device to obtain the reference zero potential of the earth, then this neutral point is called the zero point, and the wire leading from the zero point is called the neutral wire. 2. In a typical 220-volt single-phase circuit, one of the two wires is called the \"phase wire\" or \"live wire\", while the other wire is called the \"neutral wire\" or \"ground wire\". “The terms “live wire” and “ground wire” are merely common names used in practice; especially, the term “ground wire” is not accurate. Strictly speaking, it should be: if the power side of the circuit (the neutral point of the three-phase distribution transformer) is grounded, then it is called the “neutral wire”” ； If it is not grounded, it should be referred to as the \"neutral wire\" to avoid confusion with the \"ground wire\" in the grounding system. 3. In the case of a three-phase circuit, in addition to the three phase wires, another wire can be drawn from the neutral point; this wire is the neutral point itself, thereby forming a three-wire or four-wire system. The voltage between the phase wires in such a circuit is called line voltage, while the voltage between a phase wire and the neutral wire is called phase voltage. 4. Whether the neutral point is grounded, also known as the neutral point system. Neutral point systems can be roughly divided into two categories: neutral point grounded systems and neutral point insulated systems. According to IEC standards, low-voltage distribution systems are classified into three types: IT, TT, and TN. The TN system is further divided into three subtypes: TN-C, TN-S, and TN-C-S. From the above comparison, we can also determine the safety measures for different operating modes of the power grid neutral point, namely the insulated operation mode of the neutral point and the direct grounding operation mode of the neutral point. Under neutral-point insulated operation, the following must be ensured: ① All electrical equipment must be equipped with protective grounding; protective neutral grounding is not permitted ； ②The mechanical strength of the neutral wire should be the same as that of the phase wires; the neutral wire must not be disconnected ； ③The neutral current should not exceed 25% of the rated voltage of the transformer’s secondary winding, and the currents in the three phases should not differ too much to avoid affecting the balance of the phase voltages ； ④Direct grounding of the neutral wire must be prevented; three-phase insulation **devices** must be installed in low-voltage distribution panels to enable timely detection and correction of grounding faults in the low-voltage power grid ； ⑤Four surge arresters should be installed on the secondary side of the distribution transformer to prevent lightning overvoltages. In the operation mode with the neutral point directly grounded, the following must be ensured: ① All metal parts of electrical equipment that are not energized under normal conditions must be connected to either protective neutral or protective ground ； ②In the same low-voltage distribution system with a three-phase four-wire configuration, protective neutral connection and protective earth connection cannot be used interchangeably; that is, it is not allowed to use protective neutral connection in some parts of the system while using protective earth connection in other parts. However, it is permissible to use both protective neutral connection and protective earth connection on the same device, as this yields better safety results ； ③It is required that the neutral wire be grounded repeatedly, because in the event of a break in the neutral wire, the enclosures of equipment connected to the neutral wire would have a voltage of 220V relative to ground, which is absolutely not allowed. III. Differences between the neutral wire (zero wire) and the ground wire: In low-voltage power frequency circuits, there are, in simple terms, structural and principle-based differences between them. 1. Differences in structure: Neutral wire (N): The main conductor that is drawn out from the neutral point of the transformer after it is grounded. Ground wire (PE): A main conductor is drawn from the grounded neutral point of the transformer; according to standards, it is re-grounded every 20–30 meters. 2. Difference in principle: Neutral wire (N): It is mainly used in the working circuit; the voltage generated by the neutral wire equals the line resistance multiplied by the current in the working circuit. Due to long-distance transmission, the voltage generated by the neutral wire cannot be ignored, making protective measures for personal safety unreliable. Ground wire (PE): Not used in the working circuit, only as a protection wire. Utilizing the Earth’s absolute “0” voltage, when there is a leakage current from the equipment enclosure, the current quickly flows into the ground. Even in cases where the PE wire is open-circuited, the current still flows into the ground via nearby grounding electrodes. IV. In fact, there are more than just protective grounding when it comes to ground wires. Below is an introduction to ground wires. A ground wire is short for a grounding device. Ground wires can be categorized into functional grounding and safety grounding. Safety grounding, in turn, can be further divided into protective grounding, lightning protection grounding, and electromagnetic radiation protection grounding. 1. Working ground: The working ground is the grounding wire used to complete the circuit so that the equipment meets its performance requirements. For example, the radios used in every household in rural areas during the 1960s and 1970s had a ground wire, and the grounding point had to be kept wet with water regularly. Work grounding involves burying a copper conductor in the soil and then leading one end of it out of the ground using a wire; this creates a grounding system, with the requirement that the grounding resistance be ≤4Ω. 2. Protective grounding: Protective grounding is a safeguard measure taken to prevent electric shock incidents when people use household appliances and other electronic devices in offices and similar settings. The metal casings of household appliances and office equipment are equipped with grounding wires; if the insulation is damaged and the casing becomes charged, current flows along these grounding wires into the ground to ensure safety, otherwise it could pose a risk to human safety. Electrical safety regulations specify that the resistance of the protective ground connection should be ≤4Ω, while the resistance of the human body is generally greater than 2000Ω. According to Ohm’s law, when the insulation is damaged, the current flowing through the human body is only 1/500 of the total current, thereby providing protection. (The higher the voltage, the lower the human body’s resistance; in other words, under high voltage conditions, it is very likely that the body will act as a conductor, allowing current to flow through it.) 3. Lightning protection grounding: To prevent tall buildings, various communication systems, as well as antennas and other facilities installed on buildings from being struck by lightning during thunderstorms, lightning rods must be installed, and wires are used to connect them to the established lightning protection grounding system. 4. Grounding for electromagnetic radiation protection: In some critical facilities, shielding nets are installed on electronic equipment to prevent electromagnetic interference; these shielding nets must be connected to the appropriate grounding system, with the required grounding resistance being ≤4Ω.