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Design Description of Line Fault Indicators

Views: 159     Author: Site Editor     Publish Time: 2021-04-29      Origin: Site

The line fault indicator is a device used to indicate the flow of fault current in the transmission and distribution lines, power cables and switchgear inlet and outlet lines. Once the line fails, the line patrol personnel can use the alarm display of the power line fault indicator to quickly determine the fault point and eliminate the short circuit voltage fault.

power line fault indicator



1. The Working Principle of Line Fault Indicators

1) Grounding Detection

Sampling the first half wave of the capacitor current at the moment of grounding and the first half wave of the voltage at the moment of grounding, compare their phases, when the capacitor current at the moment of grounding suddenly changes and is greater than a certain value, and is in phase with the first half wave of the voltage at the moment of grounding, and the voltage drops, it is judged that the line is grounded, otherwise the line is not grounded.


2) Short Circuit Detection

According to the electric wire short circuit phenomenon, at the moment of electrical short circuit, the positive current mutation and the protection action power outage are used as the action basis.



2. Design Description of Line Fault Indicators

This circuit is designed to check whether the ground connection in the power socket is complete. The power socket must be grounded, especially if the gadget connection has a metal body. If there is any leakage from live wires, the ground connection will allow current to flow to the ground, protecting us from shocks. Therefore, this circuit can be used to check the power socket before using gadgets such as heaters, electric irons, etc. It also indicates whether there is electricity in the socket and whether the polarity of the phase and neutral wires are correct.


As you know, these three-pin power sockets have three-pin-wire, neutral wires and ground wires. The ground pin of the plug is large and long, so it will enter the socket first and eliminate any leakage current. The size of this pin is also large and can handle large currents. This circuit uses the potential difference between the neutral wire and the ground wire. The measured neutral-to-ground voltage of a single-phase circuit at the load is a function of the load current and the impedance of the neutral line. Various standards limit the voltage drop in the branch circuit to 3% (the total voltage drop of the feeder and the branch circuit is 5%) to achieve reasonable operating efficiency. Based on this, the neutral-to-ground voltage limit of a single-phase 120V AC circuit is 3.6V AC, and a single-phase 230V AC circuit is 6.6V AC.

remote fault indicators


How does this work? Simply plug the circuit into a power outlet. If the phase and neutral wires are normal, the red LED lights up. If the ground wire is intact, the green LED lights up. Therefore, if all the phase, neutral wires and ground wires are perfect, both the red and green LEDs of the cable fault indicator will light up. If the ground wire is damaged, the green LED remains off while the red LED lights up.


This circuit does not require batteries or other power sources. It draws current from the socket itself. Diodes and resistors drop the 230V alternating current and convert it into low-voltage direct current for the circuit. When the device is inserted, the base of the transistor is connected to the ground pin of the socket. When the power line is properly connected, a potential difference will be generated between the neutral wire and the ground wire, and the transistor will be turned on to light up the green LED. This shows that the ground connection is perfect. If there is electricity in the socket and the phase and neutral wires are connected correctly, the red LED lights up.


We can provide you with professional ground fault indicators, remote fault indicators and earth leakage indicators to help you find underground power short circuit faults more accurately.

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