Use a clamp-on ammeter to check leakage and electricity theft on low-voltage lines
1. Determine whether there is a problem with the residual current action protector itself
The method is: at the distribution transformer, disconnect the fuse on the phase line on the outlet side of the AC contactor that controls the low-voltage line. If the residual current action protector can operate normally at this time, it proves that the residual current action protector is good. of. Otherwise, the residual current action protector should be inspected and replaced.
2 Check to determine which phase line is leaking
The method is: at the distribution transformer, disconnect the neutral wire on the outlet side of the AC contactor that controls the low-voltage line, then install the removed fuse core on one of the phases, and use a clamp ammeter to measure the phase, the measured current 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.
3. After determining the phase line with leakage, determine the location of the leakage.
The method 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 other two phases, and use a clamp ammeter on the pole to detect the live phase line to determine the location of the 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 indication of the clamp ammeter is also zero; if there is leakage current, the clamp ammeter can detect the leakage current.
4 Check whether there is any leakage in the user’s internal circuits and equipment
The method is: use a clamp ammeter to measure the leakage current at the user's power entry line, and at the same time put the user's electrical equipment and lamps in and out one by one, and look at the clamp ammeter to detect changes in the leakage current to find the leaking equipment and lamps. . 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 on a case-by-case basis. For leakage faults in pre-buried and concealed pipelines, the only solution is to replace or rewire them.
