Inspection and Repair of Open Circuit Faults by Multimeter
When the multimeter detects the open-circuit fault of the lighting line, when the power is turned off, the multimeter can be used to block the continuity of the measurement line; or when the power is turned on, the multimeter can be used to measure the voltage of the line to determine the fault point.
The open circuit fault of the lighting circuit can be divided into three situations: total open circuit, partial open circuit and individual open circuit.
(1) All open circuits.
This type of fault mainly occurs on the main line, in the power distribution and metering devices, and within the scope of the household devices. Usually, the connection of each joint of the above-mentioned parts (including the melt terminal) should be checked in turn. Generally, the failure of the wire head to break away from the connection is the most common; secondly, check the opening and closing of the dynamic and static contacts of each line switch .
(2) Partial open circuit.
This type of fault mainly occurs within the range of branch lines. Generally, check the connection of each wire head first, and then check the shunt switch. If the cross-section of the shunt wire is small, it should be considered that the core wire may be broken in the insulating layer and cause a local open circuit.
(3) Individual open circuits.
This type of fault is generally confined to the junction box, lamp holder, light switch, and the connecting wires between them. Usually, the connection of each joint can be checked separately, and the contact condition of the contacts of components such as lamp holders, light switches and sockets (for fluorescent lamps, the connection condition of each component should be checked).
Once leakage occurs in the lighting circuit, it will not only waste electric energy, but also may cause electric shock accidents. The essence of leakage and short circuit is the same, but the degree of accident development is different. Severe leakage may cause short circuit. Therefore, the leakage of lighting lines must not be taken lightly. The insulation of the line should be checked frequently, especially when leakage is found, the cause should be found out in time, the fault point should be found, and it should be eliminated.
The main reasons for the leakage of lighting lines are: first, the insulation of wires or electrical equipment is damaged by external force; second, the long-term operation of the line leads to aging and deterioration of the insulation;
Leakage fault repair
First determine whether there is indeed a leakage. Use the R×10k block of the pointer multimeter to measure the insulation resistance of the measuring circuit, or place the digital multimeter in the AC current block (equivalent to an ammeter at this time), connect it in series to the main switch, turn on all the switches, and remove all the loads ( including light bulb). If there is current, it means that there is leakage. After confirming the leakage of the line, you can continue to check according to the following steps.
(1) Determine whether it is the leakage between the phase line and the neutral line, or the leakage between the phase line and the earth, or both. The method is to cut off the neutral line. If the ammeter indication remains unchanged, it is the leakage between the phase line and the earth; if the ammeter indication is zero, it is the leakage between the phase line and the neutral line; Leakage between line, phase line and earth.
(2) Determine the leakage range. Take off the shunt fuse or pull open the circuit breaker. If the ammeter indication remains unchanged, it means the bus leakage; if the ammeter indication is zero, it is the shunt leakage; All have leakage.
(3) Find out the leakage point. After the above inspection, turn off the switch of the lamps and lanterns of the line in turn. When a switch is turned off, the ammeter indicator returns to zero, and the branch line is leaking; if it becomes smaller, it means that there is leakage in other places besides the branch line; If the ammeter indication remains unchanged after all the lamp switches are turned off, it means that this section of the main line is leaking. By narrowing down the scope of the accident in turn, you can further check whether there is leakage at the joints of the line and where the wires pass through the wall. After finding the leakage point, the leakage fault should be eliminated in time.
Short circuit, open circuit and leakage of lighting circuit are the most common faults. Only by carrying out specific measurement and analysis can we accurately find out the fault point, determine the nature of the fault, and take effective measures to eliminate the fault as soon as possible.
