Phase-Neutral-Earth Fault Indicator Circuit

This Circuit helps you to find Open Earth, Phase or Neutral reverse in the Power source. By using simple components like Resistors and LEDs, we can create this circuit.

Circuit Diagram

earth fault indicator

Construction and Working

Four Red color LEDs are used here, and Resistors are 56KΩ / 1W. LED1 is connected between Phase and Earth through Resistor.( Here you can connect LED in any Polarity).

LED2 is connected between phase and Neutral. LED3 is connected between Earth and Neutral.

These three LEDs will show the condition of AC power supply.

LED Indication
LED1 LED2 LED3 LED4 Status
ON ON OFF - Phase Neutral Earth Wired Correctly
OFF ON ON - Wrong Polarity of Phase/Neutral
ON ON ON - Open Earth or Neutral
- - - ON Blown fuse

LED 4 connected parallel to the fuse and it glows when fuse blown and appliance being connected the power source.
 




 
Some spike and surge protector use MOV (Metal Oxide Varistor) along with this kind of circuit to protect appliance from high voltage and surge current.

3 thoughts on “Phase-Neutral-Earth Fault Indicator Circuit

  1. To test the circuit for proper functioning, check input supply at TP1 with respect to TP0. Also check the voltage difference across neutral and earth pins as per the test point table.

  2. Hello,
    i want to detect that earth terminal is connected or not. as per above circuit it is possible but when bad earth connection done or there is large voltage between earth and neutral terminal than how can i identify it.
    i want to prevent my instrument and not allow to start when there is more than 10 V between earth and neutral. Also my phase and neutral wires are not defined, it may alters.
    please help me if you have any idea

  3. Like Mr Pankaj, I also want to detect whether earth terminal is connected or not. As per above circuit it is possible but when bad earth connection exists or there is large voltage difference between earth and neutral terminals, then how can one identify it so that costly instruments do not get faulty. I think that LED3 should not light in such a case. Also how to prevent start when there is more than 10 V between earth and neutral. Please help.

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