The clamp-type ammeter for single-phase power supply is stuck on the neutral wire and the live wire at the same time, and there is leakage if there is an indication. Three-phase non-neutral power supply clamp-type ammeter stuck three live wires at the same time, there is leakage if there is a number displayed. Three-phase four-wire power supply with clamp-type ammeter stuck four lines at the same time, there is leakage if there are indications.
How to use a clamp ammeter to check the leakage and theft of low-voltage lines?
Clamp ammeter is a combination of current transformer and 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 opening of the iron core without cutting it, and the iron core is closed when the wrench is spread out.
The circuit wire under test that passes through the iron core becomes the primary coil of the current transformer, and a current is induced in the secondary coil through the current. Then the ammeter connected to the secondary coil will have an indication - measure the current of the line under test.
The clamp-type ammeter can change different ranges through the shift of the change-over switch. However, it is not allowed to operate with power on when shifting gears. The ordinary accuracy of the clamp meter is not high, and it is 2.5 to 5 in the ordinary world.
For the convenience of use, there are also switches with different ranges in the watch for measuring current of different grades and measuring voltage.
When measuring the current with a common ammeter, it is necessary to cut off the circuit before connecting the ammeter for measurement, which is very troublesome, and sometimes the normal operating motor does not allow this.
At this time, it is much more convenient to use a clamp-on ammeter, which can measure the current without cutting the circuit. A clamp-on ammeter is the best tool for checking low-voltage line leakage or checking for electricity theft.
1. Determine whether there is a problem with the residual electrical activity as the maintainer itself
Method: 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 electrical activity as a protector can be put into operation normally at this time, it is confirmed that the residual electrical activity is used for maintenance. device is good. Otherwise, it should be inspected and replaced as a protector for the residual power.
2. Introspect to determine which phase line is leaking
Method: 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, and use a clamp ammeter to measure the phase, the measured current is the leakage current of the phase. Measure the leakage current of other leakage phases in sequence in the same way.
In order to avoid the existence of phase line grounding on the line (if someone has no partial discharge power frequency test transformer, automatic transformation ratio tester, grounding continuity resistance tester, variable frequency series resonance test device, wireless high-voltage phase detector adopts the one-line-one-local method to steal. Electricity, etc.) produce high current damage to the instrument, when testing, first put the clamp-type ammeter gear on the high-current gear; if the detected value is small, then switch the clamp-type ammeter gear to milliampere for detection. From: Home of Electrotechnical Technology
3. After determining the phase line with leakage, determine the status of leakage
Method: At the distribution transformer, insert the phase line to be checked into the fuse core, disconnect the neutral line and the other two-phase fuses, and use a clamp-type ammeter to detect the live phase line to determine the leakage status. In order to improve the efficiency, the position of the pole can be selected in the middle of the line. After testing, it is determined that the leakage part is in the first half of the line or the second half of the line, and then it is detected in the line section where the leakage is suspected. And so on, reducing detection limitations.
Finally, test the insulator of the phase line within the determined smaller limit, and test the phase line of the subscriber line connected to the phase line within the limit (it can be done on the ground, or when testing the insulator). also performed) to determine the detailed location of the leakage.
