Use clamp ammeter to check low voltage line leakage and power theft
1. Determine whether there is a problem with the residual current action protector itself
The method is to disconnect the fuse on the phase line of the AC contactor that controls the low-voltage line at the distribution transformer. 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. Otherwise, the residual current operated protector should be repaired and replaced.
2. Check and determine which phase line is leaking electricity
The method is to disconnect the neutral wire on the outgoing side of the AC contactor that controls the low-voltage line at the distribution transformer, then install the removed fuse core on one of the phases, and measure the current of that phase with a clamp ammeter. The measured current is the leakage current of that phase. Measure the leakage current of the remaining leakage phases in sequence using the same method.
To prevent the occurrence of high current damage to the instrument due to phase grounding on the line (such as someone using the one line one place method to steal electricity, etc.), the clamp current meter should be set to the high current position first during detection; If the detection value is very small, switch the clamp ammeter to milliampere range for detection.
3. After identifying the phase lines with leakage, determine the location of the leakage
The method is to insert the fuse core into the phase line to be inspected at the distribution transformer, disconnect the fuses of the neutral line and the other two phases, and use a clamp ammeter to detect the leakage position of the live phase line by climbing the pole. To improve efficiency, the pole position can be selected in the middle of the line, and the leakage location can be detected to determine whether it is in the front or back half of the line, and then to the suspected leakage line section for further inspection. Similarly, narrow down the detection range. Finally, the pillar insulators of the phase line within the determined small range shall be tested, and the phase lines of the user service lines connected to the phase line within the range shall be tested (which can be carried out on the ground or simultaneously with the testing of the insulators) to determine the specific location of the leakage.
In the case of low-voltage power transmission, clamp ammeters can also be used to detect low-voltage user service lines within the suspected range. During detection, the phase and neutral wires of single-phase users should be placed in the clamp of the clamp ammeter at the same time, and the three phase and neutral wires of three-phase users should also be placed in the clamp at the same time. If there is no leakage fault, the phasor sum of the load current flux is zero, and the clamp ammeter reading is also zero; If there is leakage current, the clamp ammeter can detect the leakage current.
