What is an ELCB and where is it used

ELCB stands for earth leakage circuit breaker, it is a protective device which would suddenly switch the electricity off in case of any leakage of electricity. This device can protect the people from electric shock, ELCB is also called as RCD or safety switches. By using an ELCB we can prevent electrical shocks, chances of fire, etc. This device is mostly used in places that have high earth impedance. ELCB is capable to detect the slight amount of current which is in a faulty metal electrical equipment. If any current flows to the ground wire it is because of electrical faults and the supply of current to that appliance must be stopped so ELCB’s are used to protect the person who is in contact with the electrical device.

So basically ELCB is an electrical device that would cut off the power to the electrical appliance in case of any imbalance in the flow of electrical current between the phase and neutral conductor.

How does an ELCB operate

If the current-carrying wire accidentally touches the metallic body of the connected device or the appliance a potential is created between the earthed rod and the metallic enclosure of the device. So the ELCB will sense the difference in potential and if the potential difference reaches a certain level which could be harmful to the human body, then the ELCB will cut off the power supply from the connected device and so this way the human safety can be ensured.

How ELCB is connected

All the electrical or electronic devices must be earthed while installing, by doing so we are preventing electrocution. A metallic rod will be buried in the soil and the ELCB is connected between the wire coming from the rod and to the wire attached to the external metallic body of the electrical device. It can also be described as the ELCB is connected to the earth wire read.

What are the types of ELCB

Voltage ELCB

In this type of ELCB, the equipment will be connected to one of the relay terminals, and the other terminal is connected to the earth. In case of any insulation failure or the live wire comes in contact with the metal body of the equipment then there will be a voltage difference across the terminal of the coil connected to the equipment body and earth and due to this voltage difference current will flow to the relay coil. So if the voltage difference crosses a certain limit then ELCB will disconnect the power to the device.

Current operated ELCB

This type of ELCB is also called RCD, in this, both the supply and return conductors are run through a sensing coil. So in case of any current imbalance then the magnetic field won’t cancel equally and thus the ELCB would detect the imbalance and disconnects the device from the power supply.

What are the advantages of ELCB

  • There will be fewer nuisance trips
  • If one of the earth wires becomes disconnected from the ELCB, then it will no longer trip or the installation will often no longer be properly earthed
  • A lightning strike could cause a voltage gradient in the soil, the ELCB will detect the coil that has enough voltage to cause it to trip

What are the disadvantages of ELCB

  • ELCB can’t find the faults which don’t transfer current from the CPC to the earth rod.
  • Certain electrical leaky appliances such as water heaters, washing machines can cause the ELCB to trip
  • Extra resistance could be added by ELCB and it may also cause an earthing system failure


post-graduate in Electronics & communication.

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