Leakage current clamp meter is the best tool to check the leakage of low-voltage lines or to check electricity theft.
1 Judging whether there is a problem with the residual current operated protector itself
If the residual current action protector cannot be put into operation or is frequently protected: at the distribution transformer, use a leakage current clamp meter to clamp the three phase wires and neutral wires on the outlet side of the AC contactor or leakage circuit breaker, and activate the residual current The protector is forcibly put into operation. If the display value of the leakage current clamp meter is greater than 300mA at this time, it proves that the residual current action protector is good. At this time, use the leakage current clamp meter to judge which phase is leaking; otherwise, it should be repaired Or replace the residual current operating protector.
2. Determine which phase and phase line are leaking
At the distribution transformer, disconnect the neutral line 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 phase with a leakage current clamp meter. , the measured display value is the leakage current value of the phase. Measure the leakage current values of the other phases sequentially in the same way.
In order to prevent the occurrence of large current damage to the instrument due to the presence of phase wire grounding on the line (such as someone using the method of one line to one place to steal electricity, etc.), first set the gear of the leakage current clamp meter to the maximum range when testing; if the displayed value is small, Then switch the leakage current clamp meter range to milliampere measurement.
3 After determining the phase line with leakage, determine the location of leakage
At the distribution transformer, insert the phase wire to be checked into the fuse core, disconnect the neutral wire and the fuses of the other two phases, and use a leakage current clamp meter to measure the live phase wire to determine 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 small range, and test the phase line of the user line connected to the phase line within this range (it can be done on the ground or on the insulator at the same time) to determine the specific location of the leakage.
In the case of low-voltage line power transmission, the leakage current clamp meter for the low-voltage subscriber line within the suspected range can also be detected. When testing, the phase wire and neutral wire of single-phase users should be placed in the jaws of the leakage current clamp meter at the same time; 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, and the display value of the leakage current clamp meter is also zero; if there is a leakage current, the value of the leakage current can be detected.
4 Check the user's internal lines and equipment for leakage
Use a leakage current clamp meter to measure the leakage current value 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 current by looking at the change of the leakage current value measured by the leakage current clamp meter If all the equipment and lamps are normal, or the equipment with leakage has been withdrawn, but the leakage current clamp meter shows that the user still has leakage current, it may be that the low-voltage line of the user has leakage. It should be dealt with on a case-by-case basis. For the leakage fault of the pre-buried and concealed pipeline, only the treatment method of changing the line or rewiring can be adopted.
