How to check whether there is leakage with a clamp meter
The conductor of the circuit under test passing through the iron core becomes the primary coil of the current transformer, in which current is induced in the secondary coil. As a result, the ammeter connected to the secondary coil will have an indication to measure the current of the circuit under test. The clamp meter can be changed to different measuring ranges by turning the switch. However, it is not allowed to operate with power on when shifting gears. Clamp meters generally have low accuracy, usually level 2.5 to level 5. For ease of use, the meter also has switches of different ranges to provide the functions of measuring current and voltage at different levels.
When using a clamp ammeter to detect current, be sure to clamp a conductor (wire) being measured. If two (parallel wires) are sandwiched, the current cannot be detected. In addition, when using the center (core) detection of the clamp ammeter, the detection error is small. When checking the power consumption of home appliances, it is more convenient to use a line splitter. Some line splitters can amplify the detection current by 10 times, so currents below 1A can be amplified before detection. When using a DC clamp ammeter to detect DC current (DCA), if the current flows in the opposite direction, a negative number will be displayed. You can use this function to detect whether the car's battery is charged or discharged.
At the distribution transformer, disconnect the neutral wire on the outlet side of the AC contactor that controls the low-voltage line, install the removed fuse core on one of the phases, and measure the phase with a clamp ammeter. The current obtained is the leakage current of that phase. Measure the leakage current of the other leakage phases in sequence in the same way. In order to prevent the instrument from being damaged by large current due to phase line grounding on the line (for example, someone uses the wire-to-ground method to steal electricity, etc.), first place the clamp ammeter in the high-current position during detection; if the detection value is very small, then Switch the clamp ammeter to milliamp detection.
After determining the phase line with leakage, the method to determine the location of the leakage is: at the distribution transformer, insert the fuse core into the phase line to be checked, disconnect the fuses of the neutral line and the remaining two phases, and use the pole to climb The clamp ammeter detects the live phase line to determine the location of leakage. In order to improve efficiency, the climbing pole position can be selected in the middle of the line. Through detection, it can be determined whether the leakage part is in the first half or the second half of the line, and then the line section where the leakage is suspected is detected. By analogy, the detection range is narrowed. Finally, detect the phase line pillar insulators within a determined smaller range, and detect the subscriber line phase lines connected to the phase line within the range (this can be done on the ground, or when detecting insulators at the same time) to determine the specific location of the leakage.
In the case of low-voltage line power transmission, the clamp-type ammeter can also be used to detect the low-voltage user connection lines within the suspected range. During detection, the phase line and neutral line of single-phase users should be placed in the jaws of the clamp ammeter at the same time, and the three phase lines and neutral lines of three-phase power users should also be placed in the jaws of the clamp ammeter at the same time. If there is no leakage fault, the phasor sum of the load current magnetic flux is zero, and the clamp ammeter indication is also zero; if there is leakage current, the clamp ammeter can detect the leakage current.
The method to check whether there is leakage in the user's internal circuits and equipment is: use a clamp ammeter to measure the leakage current at the user's power incoming line. At the same time, put the user's electrical equipment and lamps in and out one by one, and detect the leakage current by looking at the clamp ammeter. changes to find leaky equipment and fixtures. If all the equipment and lamps are good, or the equipment with leakage has been removed, but the clamp ammeter shows that the user still has leakage current, it may be that the user's low-voltage line has leakage, and it should be dealt with according to the specific situation. For leakage faults in pre-buried and concealed pipelines, the only solution is to replace or rewire them.
