Making use of and detecting clamp ammeters
1. Judging whether there is a problem with the residual current operating 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-operated protector can be put into operation normally at this time, it proves that the residual current-operated protector is good. of. Otherwise, the residual current operating protector should be overhauled and replaced.
2 Check and judge 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, and then install the removed fuse core on one of the phases, and measure the voltage with a clamp ammeter. phase, the measured current is the leakage current of that phase. Measure the leakage current of the other leakage phases sequentially in the same way.
In order to prevent the presence of phase wire grounding on the line (such as someone using the one-line-one-place method to steal electricity, etc.) to cause large current damage to the instrument, first place the clamp ammeter gear on the high current gear during detection; if the detection value is small, then Switch the gear of the clamp ammeter to mA gear for detection.
3 After determining the phase line with leakage, judge the location of leakage
The method is: at the distribution transformer, insert the fuse core of the phase line to be checked, disconnect the neutral line and the fuses of the other two phases, and use a clamp ammeter to detect the live phase line to judge the leakage position. In order to improve efficiency, the position of the boarding pole can be selected in the middle of the line. Through detection, it is judged whether the leakage site 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, test the phase line post insulator within the determined smaller range, and test the phase line of the user connection line connected to the phase line within this range (it can be carried out on the ground, or on the detection insulator Simultaneously) to determine the specific location of the leakage.
In the case of low-voltage line power transmission, the clamp ammeter can also be used to detect the low-voltage user connection lines within the suspected range. When testing, the phase wires and neutral wires of single-phase users should be placed in the jaws of the clamp ammeter at the same time, and the three phase wires and neutral wires of three-phase users should also be put into the jaws at the same time. If there is no leakage fault, the phasor sum of the load current magnetic flux is zero at this time, and the indication of the clamp ammeter is also zero; if there is a leakage current, the clamp ammeter can detect the leakage current.
4 Check the user's internal lines and equipment for leakage
The method is: use a clamp ammeter to measure the leakage current at the user's power inlet line, and at the same time put the user's electrical equipment and lamps into and out one by one, and find the leakage equipment and lamps by checking the change of the leakage current with the clamp ammeter . If all the equipment and lamps are good, or the equipment with leakage has been withdrawn, but the clamp ammeter shows that the user still has leakage current, it may be that the low-voltage line of the user has leakage, and it should be handled according to the specific situation. For the leakage fault of the pre-buried and concealed pipeline, only the treatment method of changing the line or rewiring can be adopted.
