In the single-phase power supply range of the bus machine, the zero line is disconnected, the lights within the fault range are not on, and other electrical appliances cannot be used. , the phase line and the neutral line both display the phase voltage; but there is no voltage indication when measured with a voltmeter. According to the above situation, it can be determined that the neutral line is open in the single-phase power supply range. A branch of a three-phase four-wire system has a zero-line open-circuit fault. The specific manifestation is that within the power supply range of this branch line, some users' electric lights are not bright enough, fluorescent lamps cannot be started, the TV brightness is reduced, the image is reduced, and there is under-voltage protection. Appliances cannot be turned on or turned off automatically. In some users, the voltage rises significantly, the lights are particularly bright, and the fan speed of the busbar motor is accelerated. In serious cases, the lights or other electrical appliances are quickly burned out. If the above situation occurs, it can be determined that the branch zero line is open circuit. The zero-line open circuit fault occurs within the power supply range of the three-phase distribution transformer, that is, the zero-line bus is open-circuited. The specific performance is the same as the zero-line open circuit fault in the three-phase four-wire branch, but the scope is larger, the damage is more serious, and the loss is greater. The three-phase load is seriously unbalanced, the neutral line current is too large or the cross-sectional area of ​​the neutral line conductor is too small, and the neutral line is blown. The contact of the zero line connector is poor, causing sparks, which will cause the zero line to open for a long time. The zero line terminal of the bus machine distribution transformer is in poor contact with the conductor, and the maintenance is not in place, causing the zero line to open. The neutral lead wire inside the distribution transformer is open circuit. A fuse or a separate switch is installed on the neutral line of the three-phase four-wire system, and the fuse is blown or the switch is pulled open, resulting in an open circuit of the neutral line. When disconnecting the three-phase four-wire line, disconnect the neutral line first. Neutral line open circuit caused by other faults, such as strong wind blowing and breaking the neutral line, vehicle collision with poles, and pull wire causing the neutral line open circuit, etc. For three-phase four-wire power supply, single-phase loads should be distributed as evenly as possible to maintain three-phase load balance, strengthen monitoring of three-phase currents, and adjust in time if unbalance is found. The neutral current cannot be greater than a quarter of the phase current, and the cross section of the neutral conductor cannot be less than one-half of the phase. The connection of the zero line should be firm and reliable. If aluminum wires are used for the lead-in and lead-out lines of the distribution transformer and distribution screen, copper-aluminum transition clips should be used, and inspection and maintenance should be strengthened, especially night inspections should be carried out to find sparks in the joints. processed in a timely manner. It is strictly forbidden to install a fuse or a separate switch device on the neutral line of the three-phase four-wire system of the busbar unit. When disconnecting the three-phase four-wire line, the phase line should be disconnected first, and then the neutral line should be disconnected, and the wiring sequence should be reversed. In the event of a zero-line disconnection fault, the three-phase power supply should be cut off as soon as possible to reduce the accident hazard. Due to the random opening of electrical equipment, the unbalanced three-phase load is inevitable. The electrical damage caused by the disconnection of the neutral line and the incidents requiring compensation continue to occur. Therefore, the only way to strengthen the inspection and maintenance of the neutral line is to prevent problems caused by Before this happens, the safe operation of the zero line can be ensured, and disputes and economic losses can be reduced.