How to use a multimeter to detect leakage faults in lighting circuits
Once there is leakage in the lighting circuit, it not only wastes electrical energy, but may also cause electric shock accidents. The essence of leakage and short circuit is the same, only the degree of accident development is different. Severe leakage may cause short circuit. Therefore, the leakage of lighting circuits should not be taken lightly. The insulation of the circuits should be checked regularly, especially when leakage is found, the cause should be promptly identified, the fault point should be found, and eliminated.
The main reasons for leakage in lighting circuits are: firstly, the insulation of wires or electrical equipment is damaged by external forces; Secondly, the long-term operation of the line has led to insulation aging and deterioration; The third reason is that the circuit is invaded or contaminated by moisture, resulting in poor insulation.
Firstly, determine whether there is indeed a leakage. The insulation resistance can be measured using the R × 10k range of a pointer multimeter, or a digital multimeter can be placed in the AC current range (equivalent to an ammeter), connected in series to the main switch, all switches turned on, and all loads (including light bulbs) removed. If there is current, it indicates the presence of leakage. After determining the leakage of the circuit, the following steps can be followed to continue the inspection.
1. Determine whether there is leakage between the phase line and the neutral line, leakage between the phase line and the ground, or a combination of both. The method is to cut off the neutral line. If the ammeter reading remains unchanged, it is a leakage between the phase line and the ground; If the ammeter indicates zero, it is a leakage between the phase line and the neutral line; If the ammeter reading decreases but is not zero, it means that there is leakage between the phase line and the neutral line, as well as between the phase line and the ground.
2. Determine the range of leakage. Remove the shunt fuse or open the circuit breaker. If the ammeter reading remains unchanged, it indicates bus leakage; If the ammeter indicates zero, it is a branch leakage; If the ammeter reading decreases but is not zero, it indicates that there is leakage in both the bus and branch circuits.
3. Find the leakage point. After the above inspection, disconnect the switches of the lighting fixtures on the circuit in sequence. When a certain switch is disconnected, the ammeter indicates zero, indicating that the branch line is leaking electricity; If it becomes smaller, it indicates that there is leakage in other areas besides this branch line; If the ammeter reading remains unchanged after all lamp switches are turned off, it indicates that the main line is leaking electricity. By narrowing down the scope of the accident in sequence, further inspection can be conducted to determine if there is any leakage at the joints of the line and at the locations where the wires pass through the wall. After finding the leakage point, the leakage fault should be eliminated in a timely manner. The load end starts to detect step by step from the front end, checking whether the work is caused by the circuit or the component, and then it can be determined. After eliminating the short-circuit fault point, install a qualified fuse before powering on.
Short circuit, open circuit, and leakage in lighting circuits are the most common faults. Only by conducting specific measurements and analysis can we accurately identify the fault point, determine the nature of the fault, and take effective measures to eliminate the fault as soon as possible.
