Clamp type Ammeter to check whether there is leakage and theft of electricity in low-voltage lines
1. Judge whether the residual current operated protector is normal
At the distribution transformer, disconnect the fuse on the phase line 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 indicates that the residual current operated protector is good; Otherwise, the residual current operated protector should be repaired and replaced.
2. Measure leakage current
At the distribution transformer, disconnect the neutral wire on the outgoing side of the AC contactor that controls the low-voltage line. Then install the removed fuse core on one of the phases, measure the phase with a clamp Ammeter, and the measured current is the leakage current of the phase.
Finally, using the same method, measure the leakage current of the remaining leakage phases in sequence.
In order to prevent the instrument from being damaged by large current due to the grounding of phase line on the line, the clamp Ammeter gear should be placed on the large current gear before inspection; If the detection current is low, gradually reduce the gear.
3. Determine the location of leakage
After determining the phase line with leakage, the position of the leakage can be further determined.
(1) Detect at the distribution transformer.
At the distribution transformer, insert a fuse core into the phase line to be inspected, disconnect the neutral line and the fuses of the other two phases, and use a clamp meter to detect the live phase line on the pole to determine the leakage position.
To improve efficiency, the pole mounting position can be selected in the middle of the line, and the leakage position can be determined by detecting whether it is in the first or second half of the line. Then, it can be detected in the suspected leakage section of the line, and so on, reducing the detection range.
Finally, the pillar insulators of the phase line within a determined small range shall be tested, and the user line phase lines connected to the phase line within this range shall be tested, either on the ground or simultaneously with the insulation detection to determine the specific location of leakage.
(2) Detect at the user's wiring.
In the case of power transmission on low-voltage lines, a clamp meter can also be used to detect the connecting wires of low-voltage user lines that have determined the suspected range.
During the detection, the phase line and neutral line of the Single-phase electric power user shall be placed in the jaw of the clamp meter at the same time, and the three phase lines and neutral lines of the Three-phase electric power shall also be placed in the jaw at the same time.
If there is no leakage fault, then the vector sum of the load current magnetic flux is zero, and the indication of the clamp meter is also zero; If there is leakage current, the clamp Ammeter can detect the leakage current.
4. Check whether the user's internal lines and equipment have leakage
The specific method is to use a clamp meter to measure the leakage current at the incoming line of the user's power supply, and at the same time, put the user's electrical equipment and lamps into and out one by one. By checking the changes in the leakage current with the clamp meter, the leakage equipment and lamps can be found.
If all the equipment and lamps detected are in good condition, or the equipment with leakage has exited, but the clamp Ammeter shows that the user still has leakage current, it is possible that the low-voltage line of the user has leakage, which should be handled according to the specific situation.
For leakage faults in pre buried and concealed pipelines, only replacement or rewiring can be adopted
Processing method.
5. Precautions for checking for leakage and theft
When searching for leakage faults, the AC contactor controlling the low-voltage line needs to be forcefully powered on for a short period of time.
