The Method of Checking Leakage and Stealing Electricity with Clamp Ammeter
The clamp ammeter is a powerful tool for checking low-voltage line leakage or checking electricity theft.
Judging whether there is a problem with the residual current operating protector itself
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. Otherwise, the residual current operating protector should be overhauled and replaced.
Check and judge which phase line is leaking
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, measure the phase with a clamp ammeter, and measure The current is the leakage current of the phase. In order to prevent the presence of phase wire grounding on the line (such as someone using the method of one line one place to steal electricity, etc.) to cause a large current to damage the instrument, first put the clamp ammeter gear on the high current gear when testing; if the detection value is small, then Switch the gear of the clamp ammeter to mA gear for detection.
After determining the phase line with leakage, judge the location of leakage
At the distribution transformer, insert the fuse core to the phase line to be checked, disconnect the neutral line from the fuses of the other two phases, and use a clamp ammeter to detect the live phase line to determine the leakage position. In the case of low-voltage line power transmission, the clamp ammeter can also be used to detect the low-voltage subscriber line within the suspected range. When testing, the phase wire and neutral wire 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 clamp ammeter indicates zero, otherwise it is not zero.
Check the user's internal lines and equipment for leakage
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 by checking the change of the leakage current with the clamp ammeter. If all the equipment is 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.
Issues to be aware of
1. When looking for leakage faults, the AC contactor controlling the low-voltage line needs to be forced to send power in a short time.
2. Pay attention to safety when looking for leakage faults. Someone must supervise and take safety measures. When reading the data of the clamp ammeter, be sure to keep a safe distance between the human body and the live parts.
3. High-order harmonics interfere with a small number of residual current-operated protectors, which may cause them to malfunction. If there are large harmonic source users such as intermediate frequency furnaces in the station area, such users should be withdrawn from operation during detection.
4. This method is particularly effective for finding "one line, one place" electric thieves. Its characteristic is that the clamp ammeter shows a large leakage current, reaching hundreds of milliamperes to several amperes. Unknown electricity stealers can be searched according to the above method, and those who are suspected of such electricity stealing can go directly to their household wires to check with a clamp ammeter.
