How to Use Clamp Ammeter to Diagnose Grounding Fault Points in Low-voltage Power Grid
In low-voltage power grids, when a ground fault occurs in a distribution circuit or electrical equipment, it is difficult to identify the specific ground fault point. The method of measuring leakage current with a clamp ammeter is used to determine ground faults. No wiring or power outage is required. The operation is simple and the fault point can be found quickly and accurately.
How to Use Clamp Ammeter to Diagnose Grounding Fault Points in Low-voltage Power Grid
How to operate
In the low-voltage distribution network, if a ground fault occurs, you can first test the power supply in phases on the main power switch QS in the power distribution room (you can temporarily remove the other two-phase fuses), and then use a clamp ammeter ( It is best to use a clamp-type ammeter with a milliamp block, or wind the measured wire around the clamp core a few more turns) on the neutral point grounding wire of the distribution transformer to measure the leakage current of each phase circuit respectively. The phase circuit with the large leakage current can be judged as a circuit with a ground fault point.
After determining the phase circuit with a ground fault, first test the main line of the circuit. Check whether there are any broken overhead conductors that have fallen to the ground or are connected to pull wires, telephone lines, broadcast lines, etc., or whether the faulty phase circuit is directly connected to the neutral line, causing a single-phase grounding short circuit fault. Such grounding fault points are obvious and easy to find. If the fault is not on the main line, you can use a clamp ammeter to check each phase branch line.
. When there is current in a certain branch line but no current in the other branch circuits, it can be determined that the branch circuit with current has a ground leakage fault.
Then use the "bisection method" to detect the branch line, that is, find a test point from about half of the circuit that is easy to detect, and use a clamp ammeter to clamp the phase conductor. If there is current at the test point, it means that the fault point is The load side of the test point; if no current or very weak current is measured at the test point, it means that the ground point is on the power side of the test point. After determining which section of the circuit the fault point is located, use the above method to detect and judge from the middle of this section of the circuit, thus gradually narrowing the scope of ground fault occurrence. When you find the dividing point between the presence and absence of current, this point is the ground fault point to look for.
