The use of a multimeter for the detection of leakage faults in lighting circuits
Once leakage occurs in lighting circuits, it not only wastes electrical energy, but may also cause electric shock accidents. The essence of leakage and short circuit is the same, but the degree of accident development is different. Serious leakage may cause short circuit. Therefore, we must not take the leakage of lighting circuits lightly. The insulation of the circuit should be checked frequently. Especially when leakage is found, the cause should be found out in time, the fault point should be found, and eliminated.
The main causes of leakage in lighting circuits are: first, the insulation of wires or electrical equipment is damaged by external forces; second, the long-term operation of the circuit leads to aging and deterioration of the insulation; third, the circuit is invaded by moisture or contaminated, resulting in poor insulation.
First, determine whether there is indeed a leakage. The insulation resistance can be measured using the R×10k range of a pointer multimeter, or the digital multimeter can be placed in the AC current range (equivalent to an ammeter at this time), connected in series to the main switch, turn on all switches, and remove all loads (including Light bulb). If there is current, it means there is leakage. After confirming that the circuit is leaking, you can continue to check according to the following steps.
1. Determine whether there is leakage between the phase line and the neutral line, leakage between the phase line and the ground, or both. The method is to cut off the neutral line. If the ammeter indication does not change, it means there is leakage between the phase line and the earth; if the ammeter indication is zero, it means there is leakage between the phase line and the neutral line; if the ammeter indication becomes smaller but not zero, it means there is leakage between the phase line and the zero line. There is leakage between wires, phase wires and the earth.
2. Determine the leakage range. Remove the shunt fuse or pull open the circuit breaker. If the ammeter indication does not change, it means bus leakage; if the ammeter indication is zero, it means shunt leakage; if the ammeter indication becomes smaller but not zero, it means bus or shunt leakage. All have leakage.
3. Find the leakage point. After the above inspection, turn off the switches of the lamps on the line in turn. When a certain switch is turned off, the ammeter indication returns to zero, which means the branch line is leaking; if it becomes smaller, it means that in addition to the leakage of this branch line, there is leakage elsewhere; If the ammeter indication remains unchanged after all the light switches are turned off, it means there is leakage in this section of the trunk line. By narrowing the scope of the accident in turn, you can further check whether there is leakage at the joints of this section of the line and where the wires pass through the wall. After finding the leakage point, the leakage fault should be eliminated in time. The load end starts to detect step by step towards the front end to see whether the work is caused by the circuit or the components, and then you can judge. After eliminating the short circuit fault point, install a qualified fuse before powering on.
Short circuit, open circuit, and leakage of lighting circuits are the most common faults. Only by conducting specific measurements 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.
