How to use a clamp ammeter to check for leakage and theft issues in low-voltage lines?
A clamp type ammeter is a combination of a current transformer and an ammeter. The iron core of the current transformer can be opened when the wrench is tightened; The wire through which the measured current passes can pass through the open gap of the iron core without cutting it, and when the wrench is unfolded, the iron core closes.
The tested circuit wire passing through the iron core becomes the primary coil of the current transformer, and the current passing through it induces a current in the secondary coil. Then, the ammeter that connects the secondary coils has an indicator to measure the current of the tested circuit.
The clamp type ammeter can be shifted to different ranges through the shift switch. but
It is not allowed to operate with power when shifting gears. The precision of clamp shaped watches is not high in general, ranging from 2.5 to 5 levels.
For convenience of use, there are also conversion switches with different ranges in the meter for measuring different grades of current and voltage.
When using a popular ammeter to measure current, it is necessary to cut off the circuit and shut it down before connecting the ammeter for measurement. This is very cumbersome, and sometimes normal operating electrical machines do not allow this.
At this point, using a clamp type ammeter becomes much more convenient, as it can measure current without cutting the circuit. A clamp ammeter is the best thing to reflect on low voltage line leakage or detect theft.
1. Identify whether there is a problem with the residual electrical activity maintenance device itself
Method: At the distribution transformer, disconnect the fuse on the phase line of the AC contactor on the output side of the low-voltage line. If the residual power action maintenance device can be put into operation normally at this time, it is confirmed that the residual power action maintenance device is good. Otherwise, it is necessary to check and modify the maintenance device for replacing residual electrical activities.
2. Reflect on which phase line is causing leakage
Method: At the distribution transformer, disconnect the neutral wire on the outlet side of the AC contactor of the low-voltage line, and then install the removed fuse core on one of the phases. Use a clamp ammeter to measure the phase, and the measured current is the leakage current of that phase. Measure the leakage current of other leakage phases in sequence using the same method.
To avoid the occurrence of high current damage to the instrument due to phase grounding on the line (if there is no partial discharge power frequency test transformer, fully automatic transformer ratio tester, ground continuity resistance tester, variable frequency series resonance test device, wireless high voltage nuclear phase transformer using the one-to-one local method for stealing electricity, etc.), the clamp type ammeter should be placed in the high current position before detection; If the detection value is very small, then switch the clamp ammeter gear to milliampere gear for detection. From: Home of Electrical Technology
3. After determining the phase line with leakage, determine the status of leakage
Method: At the distribution transformer, insert a fuse core into the phase line to be reflected, disconnect the neutral line and other two-phase fuses, and use a clamp ammeter to detect the live phase line on the pole to determine the leakage status. To improve efficiency, the pole climbing position can be selected in the middle of the line. After testing, it is determined whether the leakage position is in the first half or the second half of the line, and then it is detected in the suspected leakage section of the line. By analogy, reduce detection limitations.
Finally, the pillar insulator of the phase line within the determined small limit shall be tested, and the user's household line phase line connected to the phase line within the limit shall be tested (either above ground or during insulation detection) to determine the detailed location of leakage.
