Method of detecting leakage and stealing electricity with clamp ammeter
At the distribution transformer, disconnect the fuse on the phase line of the outlet side of the AC contactor that controls the low-voltage line. If the residual current action protector can be put into operation normally at this time, it proves that the residual current action protector is good. Otherwise, the residual current action protector should be overhauled and replaced.
Check and judge which phase line is leaking electricity.
At the distribution transformer, disconnect the neutral line on the outlet side of the AC contactor that controls the low-voltage line, then install the removed fuse core on one of the phases, and measure the phase with a clamp ammeter. The measured current is the leakage current of the phase. In order to prevent the instrument from being damaged by high current caused by phase grounding (for example, someone steals electricity by one wire and one ground) on the line, first put the clamp ammeter gear on the high current gear during detection; If the detection value is very small, switch the clamp ammeter gear to mA gear for detection.
After determining the phase line with leakage, judge the location of leakage.
At the distribution transformer, plug the phase line to be inspected into the fuse core, disconnect the neutral line from the fuses of the other two phases, and check the live phase line with a clamp ammeter 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 user connection line within the suspected range. When testing, the phase and neutral wires of single-phase users should be placed in the jaws of clamp ammeter at the same time, and the three phase 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 clamp ammeter indicates zero, otherwise it is not zero.
Check the user's internal wiring and equipment for leakage.
Measure the leakage current at the user's power inlet line with a clamp ammeter, and at the same time put the user's electrical equipment and lamps in and out one by one, and find the leakage equipment by watching the clamp ammeter detect the change of leakage current. If all the equipment is good, or the equipment with leakage has been withdrawn, but the clamp ammeter shows that the user still has leakage current, it may be that the user's low-voltage line has leakage, which should be handled according to the specific situation.
Problems needing attention
1. When finding the leakage fault, it takes a short time to forcibly send power to control the AC contactor of the low-voltage line.
2. Pay attention to safety when finding the leakage fault, and someone must monitor it and take safety measures. When reading the data of clamp ammeter, we must keep a safe distance between human body and charged parts.
3. Higher harmonics interfere with a few residual current action protectors, which may cause misoperation. If there are large harmonic source users such as intermediate frequency furnace in the station area, such users should be withdrawn from operation during detection.
4. This method is particularly effective for finding "one line and one place" electricity thieves. Its characteristic is that the clamp ammeter shows a large leakage current, reaching several hundred milliamps to several amperes. Unknown electricity thieves can be searched according to the above method, and those who are suspected of stealing electricity can be directly checked at the connection line with clamp ammeter.
