What's the matter with the live wire testing the zero wire with a test pen?
First of all, it should be clear that no matter whether the live wire (the technical term is the phase wire) is disconnected or not, the neutral wire will not be charged under normal circumstances. If the neutral line is charged, it means that there is a problem somewhere in the line, so how to find out where the problem is? For ordinary customers who use electricity, share a simple and practical quick search and processing method:
1. For the description of this problem, because the zero line is slightly bright, the reason for this phenomenon is generally the oxidation phenomenon at the lap joint of the zero line, resulting in poor contact, but this situation can be ruled out as the zero line disconnection of the main line , because the zero line of the main line is disconnected or the contact is poor, the fault phenomenon and consequences caused are different, so we will not analyze it here.
2. Search by section and narrow down the scope. First, check whether the neutral line of the upper and lower pile heads of the switch is normal when the main switch is in the closing position. If the neutral line is normal and there is no power, it is generally a problem in the rear section of the switch. You can check the connectors on the line section by section. After finding the fault point, re-wire and bandage it. Because the problem is usually in the line connection. This kind of situation occurs the most, and it is usually an old power line from a long time ago. Now the indoor wiring and installation are very scientific, and generally this kind of problem will not occur.
3. If when checking the switch on and off the pile, there is no power on the zero line at the top of the pile, but there is power on the bottom of the pile. In this case, the switch is generally broken. You can open and close the switch several times. Sometimes the power can be restored temporarily, but it should be Replace the switch in time.
If the neutral line on the switch is also charged during the inspection, you can only call for repairs in this case, because there may be inspections by climbing poles, and the user cannot easily solve it.
There are two possibilities. First, in order to allow users to find the switch position smoothly in the dark, some wall switches have an indicator light connected to the switch. When the switch is off, the indicator light is still on. A small current is passed through the switch. Second, for all fluorescent lamps, whether they are ordinary fluorescent tubes or energy-saving lamps, the phosphor powder has a certain delay extinguishing characteristic, which is called "afterglow". Now that science has advanced, with liquid crystal displays and corresponding display circuits, it is easy to display things that are not happening at the same time on the same screen. For example, an electrocardiogram monitor displays a horizontal line that fluctuates up and down with the heartbeat. In fact, all the fluctuations on this horizontal line do not happen at the same moment, but have a time process. In the era when there were only CRT monitors in the past, there was only one point fluctuating with the beating of the heart. In order to display a line, a "long afterglow" display had to be used, so that the scanning point did not go out immediately after passing through, but reappeared after a long period of time. Turning off slowly makes the movement of a point become a line display. The oscilloscope at that time was also based on the same principle.
The neutral line is the loop of all electrical equipment. Since the neutral line has a certain resistance, the greater the resistance of the neutral line or the greater the current of the neutral line, the higher the corresponding voltage above. Therefore, the zero line is not completely without voltage, and it is also possible that the test pen is slightly bright. Of course, if the neutral line circuit has poor contact, etc., the neutral line voltage will be high. So it is best to measure the voltage with a voltmeter.
An open circuit of the fuse of one phase of the transformer will also cause the neutral line to be slightly bright when measured with an electric pen. When a motor burns out and one phase far out of the line is grounded through the motor, it will also cause the zero line to be slightly bright when measured by the electric pen. When the neutral line is disconnected from the power supply and passes through the electrical appliance, it will also measure the neutral line with electricity, and the electric pen is relatively bright.
It's very simple, as long as the neutral circuit is well-conducted, it is impossible for this phenomenon to occur. If this phenomenon occurs, there must be a disconnection or poor conduction somewhere in the neutral line circuit, or the electrical appliances are connected in series. The solution is to firmly connect the disconnected or poorly conducted parts of the neutral circuit. If two electrical appliances are connected in series in one circuit, one electrical appliance will be cut off and only one electrical appliance will be kept.
