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CZ series surge protector is suitable for PT, IT, IT-S, TN-S, TN-C, TN-C-S and other power supply systems with AC 50/60Hz, 220/400V and below. The design is based on the requirements of IEC61643-A, GB18802.1, GB50057, and is usually installed in the low-voltage main distribution cabinet of the building incoming line.
Under normal circumstances, whether there is electricity in the zero line, many people will argue about this. Anyway, on two points, one has electricity; one has no electricity. Regarding the lack of electricity, it actually confuses the concept of electrification, but only considers that it has electricity or no electricity from its own point of view.
Those who think that the zero line has no electricity will think that the zero line will not be an electric person under normal circumstances, so there is no electricity; it is believed that the zero line has electricity because the normal circuit has electricity everywhere, if there is no electricity It is also zero potential point where there is no electricity.
Personally think that the zero line is powered even under normal working conditions, even if the zero line is grounded at the transformer, it is the zero potential point. As long as there is current in the whole circuit, there is voltage at a certain point in the loop. Since there is voltage, it is charged. In short, if there is current, there is voltage, then it is charged. After all, the wires are not completely without resistance, even if they are small, but there are.
The view that there is no electricity is somewhat misunderstood. If you don't have electricity, it doesn't mean there is no electricity. For example, the dry battery does not power people, but it has electricity. People often say that no electricity just means that the voltage is small, not that there is no electricity at all.
The usual zero line does not really charge people, but in some cases, the zero line is the same as the fire line, and it also carries a very high voltage, such as the following:
When the neutral line is disconnected, it turns out to be the part of the neutral line. It is now possible to bring the same voltage as the live line (such as 220V). When the neutral line is disconnected at the same time, and the switch of the electric device is closed, the zero line is brought with the voltage of 220V. At this time, the electric equipment such as the bulb is not bright, but it is dangerous, then touch An accident will occur in the original zero line. The consumer equipment will only work when there is current flowing, only the voltage is not working. The generation of voltage does not require a complete loop, and the generation of current requires a complete loop. The neutral line is broken and the current is lost.
Therefore, the normal use of electrical equipment does not work, do not touch the repair directly, but also to judge whether it is because of equipment problems or the problem of the zero line. Judging is also very simple, to see if other electrical equipment in the home can work properly. If all the devices are not working, it is either a power failure or a zero line or the fire line is broken. The fire line is broken, people are very vigilant about the fire line, that is, the zero line is broken, it is easy for people to make false judgments, and it is easy to cause irreparable disasters.
How to prevent the zero line charging? There are 8 major links to note below!
1. The three-phase load should be kept as balanced as possible. The imbalance should not exceed 20% regardless of the load of the main line or branch line, otherwise the voltage loss and power loss will be greatly increased.
2. The connection between the neutral wire and the neutral point of the transformer must be firm and reliable. If the neutral wire is aluminum wire, it should be taken seriously when connecting. When the wire diameter exceeds 16mm2, the aluminum wire should be crimped through the aluminum terminal to ensure the neutral wire. Good electrical conductivity. Then connect with the neutral point terminal block to prevent the aluminum wire from being crimped onto the neutral point grounding bolt by the winding method. Because the surface of the aluminum wire is easily exposed to electricity due to oxidation or corrosion.
3. It is strictly forbidden to install a fuse at the neutral point of the three-phase four-wire system to prevent the fuse from being blown to form a “zero-break” for various reasons. Otherwise, the single-phase electrical device connected to the circuit may burn out due to excessive voltage, or the voltage may be too low to play a role. Therefore, switches and fuses must not be installed on the zero line, but the fuses must be installed on the zero line of the single-phase power supply line. This is because the zero line only works, and the bipolar knife should be installed on the phase and neutral lines at the same time. Switches and fuses. If the line and the neutral are connected to each other when the external line is overhauled, the fuse on the line still protects. If the fuse is only installed on the phase line, the phase line has become the neutral line. When a ground fault occurs, the short-circuit current does not pass through the fuse, and the fault will always exist, posing a threat to the system.
4. The grounding resistance of the neutral point must be qualified. The grounding resistance should meet the requirements. Every year, the electrical spring and autumn inspection time is used to check and measure all the transformer resistance (the transformer of 100KV and above should be no more than 4Ω, the transformer of 100KV or less should be no more than 10Ω), and the maintenance and maintenance work of the neutral line should be strengthened. Regular inspection is carried out. And tighten the neutral point bolt of the transformer to prevent poor contact of the neutral line.
5. It should be ensured that the zero line has sufficient cross-sectional area and strength is generally not less than 50% of the cross-sectional area of the phase line, usually about 60% of the cross-sectional area of the phase line, and should meet the requirements of mechanical strength. Joints should be avoided on the zero line. When it cannot be avoided, it should be carefully connected according to the process requirements.
6. The zero line enters the switch box and the repeated grounding repeating grounding resistance is not less than 10Ω. As shown in the figure, in the case where there is no repeated grounding, the zero line behind the disconnect and all the zero-connected devices on the ground voltage are:
Where RN, RP, and RL are respectively connected to the resistor, the body resistance, and the load resistor; U is the phase voltage. If U=220V, RN=4Ω, RP=1500Ω, and RL=484Ω (rated power is 400W), UE=166V can be obtained according to the above formula. The risk of electric shock is relatively high. Moreover, the greater the unbalanced load, the higher the fault voltage, and the greater the risk of electric shock.
In the case of repeated grounding, the neutral line behind the disconnect and all the zero-connected devices on the ground are:
Where RC is the repeated ground resistance. If RC=10Ω is known and the other conditions are the same, the fault voltage can be obtained as UE=4.4V according to the above formula. It can be seen that the fault voltage is greatly reduced, and the risk of electric shock is greatly reduced or eliminated.
7. The phase and neutral lines should be connected correctly to avoid mistakes. If the phase line and the neutral line are connected to each other, the voltage of the single-phase power device will rise to 380V, causing the device to burn out. There are individual users in the living area. In order to achieve the purpose of stealing electricity, the lighting phase line is led to the interior from the corridor. Thus, in the case where the total zero line of the layer is blown, if it is not the same phase power supply, the phase voltage at this time will become the line voltage, which will be directly applied to both ends of the load, causing the device to burn out. Three-phase four-wire system load, especially for electric motors, may cause motor torque to decrease or even burn out due to lack of phase when the phase and neutral lines are connected incorrectly.
8. Minimize line terminal connections and connectors on the neutral line and minimize the number of switches and contacts in series to prevent the risk of “zeroing” due to poor contact.
In short, in the three-phase four-wire system, the neutral line is very harmful, which often leads to personal and equipment accidents. Especially in the living area, the transformer lead-out lines are three-phase four-wire system, and the load bias is relatively serious. In order to avoid accidents, it is necessary to check the neutral line frequently, and repeat grounding at each household end. In addition, the leakage protection type can be used to open, so that in the case of a zero line disconnection, the empty meeting automatically trips, as far as possible. Ensure the safety of equipment and personnel to ensure normal and stable use of electricity.