Use a multimeter to measure whether the circuit is short-circuited or grounded
A multimeter measures the current in the ground wire. If there is current in the ground wire, then the phase wire is grounded. If there is no obvious current value in the ground wire, check whether there is current in the neutral wire after confirming that no electrical equipment is working. If there is current, it means that the phase wires are short-circuited between phases or the phase wires are short-circuited to the neutral wire.
This measurement method is the most direct. If the power has been cut off and the current cannot be detected, you can consider using the resistance range of a multimeter to check the resistance between the neutral wire and the live wire, the resistance between the neutral wire and the ground wire, The resistance between the live wire and the neutral wire. Of course, if it is a 380V power supply, you also need to check the phase-to-phase resistance between the live wire.
Of course, different power supply methods will lead to different conclusions. In the TT power supply system, the neutral wire needs to be grounded separately before entering the home. The metal shell of the electrical equipment also needs to be grounded separately. At this time, measure the neutral wire and ground. The resistance between wires is normally relatively low, which means that the neutral wire, ground wire, and live wire are short-circuited. The result of your inspection is that the resistance between the neutral wire and the live wire, and the ground wire and the live wire are relatively low. You can Remove the grounding when the neutral line enters the home and then check.
The TN-S power supply system is a three-phase five-wire system, with three live wires, ground wires, and neutral wires. At this time, there will be a certain resistance value between the neutral wire and the ground wire. The same method is required when checking. Cut off the ground wire or neutral wire, and then use a multimeter to check the resistance between the neutral wire and the live wire, the ground wire and the live wire, and the live wire between phases to determine where the short circuit is.
If it is a TN-C system, it is relatively simple. The neutral wire and the ground wire are one wire, PEN. You only need to check the resistance between the live wires and the PEN wire and the live wire.
In addition, it needs to be explained: the most effective tool for checking short circuits is not a multimeter. You should use a megger corresponding to the voltage level to check.
