1 Determine whether there is a problem with the residual current action protector itself. Leakage current clamp meter
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 the residual current action The protector is forcibly put into operation. If the displayed value of the leakage current clamp meter is greater than 300mA at this time, it proves that the residual current operation protector is good. At this time, the leakage current clamp meter should be used to determine which phase is leaking; otherwise, it should be repaired Or replace the residual current action protector.
2 Determine which phase line is leaking leakage current clamp meter
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 phase with a leakage current clamp meter , the measured display value is the leakage current value of the phase. In the same way, measure the leakage current values of the remaining phases in turn.
In order to prevent the presence of phase line grounding on the line (such as someone stealing electricity by one-line-one-ground method, etc.) and damage the meter due to high current, first place the leakage current clamp meter on the maximum range during detection; if the displayed value is small, Then switch the leakage current clamp meter range to milliamp measurement.
3 After determining the phase line with leakage current, determine the position of leakage current. Leakage current clamp meter
At the distribution transformer, plug the phase line to be checked into the fuse core, the neutral line and the fuses of the other two phases are disconnected, and use a leakage current clamp meter to measure the live phase line to determine the leakage position. In order to improve the rate, the position of the pole can be selected in the middle of the line, and the leakage part is judged in the first half or the second half of the line through detection, and then go to the line section where the leakage is suspected. And so on to narrow the detection range. Finally, test the phase line pillar insulators within the determined smaller range, and test the phase lines of the subscriber line connected to the phase line within the range (it can be done on the ground, or the insulators can be tested. time at the same time) to determine the specific part of the leakage.
In the case of low-voltage line power transmission, the leakage current clamp meter for low-voltage user access lines within the suspected range can also be detected. When testing, the phase and neutral wires 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 placed in the jaws at the same time. If there is no leakage fault, the phasor sum of the magnetic flux of the load current is zero, and the display value of the leakage current clamp meter is also zero; if there is leakage current, the magnitude of the leakage current value can be detected.
4 Check the user's internal circuit and equipment for leakage current leakage current clamp meter
Measure the leakage current value with a leakage current clamp meter at the user's power inlet line, and at the same time put the user's electrical equipment and lamps in 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 there is leakage in the low-voltage line of the user. It should be handled on a case-by-case basis. For the leakage fault of pre-buried and hidden pipelines, the only way to deal with it is to change the line or re-wiring.
