What Is An Earth Leakage Circuit Breaker (ELCB)?

What Is An Earth Leakage Circuit Breaker (ELCB)?


Lately, I was curious about Earth Leakage Breakers. So, I decided to spend some time researching. I learnt what EXACTLY is an Earth leakage Circuit Breaker? And how does it function?

Now it’s time to share my findings.

What Is An Earth Leakage Circuit Breaker (ELCB)?

An Earth Leakage Circuit Breaker is a safety gadget often installed in electric circuits with high earth impedance. It prevents electric shock.

For sure: An ELCB belongs to the circuit breaker family.

Just like any other circuit breaker, an ELCB also serves some specific purpose.

And that is…

To detect current leaking and protect us from electrocution!

A BIG responsibility, right?

If you are someone who doesn’t know much about the ELCBs and find this term confusing, let your hair loose.

In the rest of the article, I am going to discuss ELCBs in great detail.

Are you ready? (I hope you are!)

Let’s dig deep in.

Earth Leakage Circuit Breaker (ELCB) – Explained!

Earth Leakage Circuit Breaker, also known as ELCB, breaks the circuit whenever it detects any current leakage.

The reasons for the leaking current can be many.

Such as an unintentional electrical connection – between the ground and the energized appliance!

Or faulty insulation.

ELCBs feature a relay coil. One end of this relay coil is connected to the metallic enclosure of the electrical appliance. The other end is earthed.

When an ELCB interrupts the circuit, the person or the pet touching the faulty device doesn’t get the electric shock.

Operation of Earth Leakage Circuit Breaker (ELCB)

An ELCB is a specialized form of a latching relay.

Normally, the main power supplies of the building are connected to the switching contacts of the ELCB.

It detects the hazardous condition in the circuit it is installed.

Whenever the ELCB detects any leakage fault from the live wire to the earth wire, it switches off the power.

And, it remains in this tripped condition until manually reset.

However, a voltage-sensing ELCB doesn’t detect fault current from a live wire to any other earthed body.

History of the Earth Leakage Circuit Breaker (ELCB)

We’re now at the most interesting part of our topic!

Why? Read it and you’ll know.

Earth Leakage Circuit Breakers (ELCBs) are quite a new invention in the electric field.

ELCBs were invented about sixty years ago.

Yes, you guessed that right the first invented ELCBs were Voltage Operated.

And you know what…

Right after the invention of the Voltage Operated ELCBs, they became one of the most widely installed electrical safety devices.

However, these Voltage Operated ELCBs were not efficient in sensing fault current from any other earthed body. This downside urged the need for a more advanced protective device.

Therefore, just after twenty years of the invention of Voltage Operated ELCBs, Current Operated ELCBs were introduced.

For several years, people have been mixing up the application of both types of ELCBs.

But, now things have changed, and there’s no more confusion.

To keep you out of this nuance below is a breakdown of both types of ELCBs.

Types of Earth Leakage Circuit Breakers (ELCBs):

 Earth Leakage Circuit Breakers (ELCBs) are of two types.

  1. Voltage Operated ELCBs
  2. Current Operated ELCBs

Voltage Operated ELCBs:

Voltage Operated ELCBs determine a rise in potential between the protected current path. Like metal frames and enclosures and the distant Earth electrode.

These devices functioned when the current actually passed through the ELCB.

Voltage Operated ELCBs were once used widely. Now they are obsolete, though.

Voltage Operated ELCBs Work Principle:

Voltage Operated ELCBs featured relay coils.

As mentioned earlier, their one end was linked with a metallic load body.

The other?

It was connected to the ground wire.

When the voltage of the equipment’s body goes up, this rise  causes a difference between earth and load body voltage.

Consequences: The high danger of electric shock!


Because the Voltage-ELCB was there, the difference in the voltage, when it exceeded the 50 Volts, would move the current relay.

The current relay, in return, would disconnect the supply current.

Thus, one could avoid the danger of electric shock.

Advantages of Voltage Operated ELCBs:

There is only one advantage of the traditional VO-ELCBs over the modern RCBs.

  • Voltage Operated ELCBs are less sensitive to earth faults than Current Operated ELCBs. So, there are fewer chances of nuisance tripping.

Disadvantages of Voltage Operated ELCBs:

Some of the disadvantages of the ELCBs are:

  • A wire break, either in the fault to load section or in the earth to ground section, will disable the working of ELCB.
  • The installation requires an additional – third wire – from the load to the ELCB.
  • If the protected system comes in contact with any additional connection to Earth, this situation can disable the detector.
  • The ELCBs can detect equipment faults only. ELCBs can’t detect if a person touches its energized part by mistake.
  • You may experience nuisance tripping if there is a light striking during a thunderstorm.
  • Leaky appliances can cause leakage current to pass through the terminal connected to the ground. Water heaters or immersion heaters, for instance.

This condition can also induce nuisance tripping.

Current Operated ELCBs (RCCBs/RCDs):

RCCBs or RCDs are the most common type of ELCBs used these days.

This kind of ELCB features a current transformer that has numerous primary windings and one secondary winding.

The two main windings are: Neutral and Line wires.

A wire-wound coil is known as the minor winding.

In normal conditions, the electric flow through this minor winding is ‘0’.

Current Operated ELCBs Work Principle:

In a stable working condition…

The flux buildup to the current over the phase wire deactivates by the current coming through the neutral wire.

In the meantime, the current flowing from the phase wire returns to the neutral.

When an error happens, a little current flees into the ground.

In this error, there arises confusion between line and neutral current. That makes an unstable magnetic field.

And that magnetic field boosts a current flow through the minor winding linked with the sensing circuit.


The current outflow gets detected, and it directs the signal to the tripping system.

How to connect the Earth Leakage Circuit Breaker?

The Earth Leakage Circuit Breaker (ELCB) accepts the connection to the Earth rod by linking to its two Earth terminals.

One goes to the fitting Earth Circuit Protective Conductor also called CPC.

The other goes to the Earth rod or other kinds of earthed connections if there are any.

Hence, the Earth circuit makes the operation of the ELCB possible through its sense coil. 

Simple as that!

Step-by-Step Process of Checking Earth Leakage Circuit Breaker

Earth Leakage Circuit Breakers need an annual checkup.

Here is a gradual process to examine your ELCBs. If you find your ELCB is not working properly, contact any service engineers nearby at once.

  • Every circuit breaker remains in the ‘ON’ position. So, deactivate the breaker first.
  • Push the operation switch to turn the power supply off.
  • Next, push the Test Button of the Earth Leakage Circuit Breaker with a pointy object. A wooden stick or a ballpoint pen, for instance.
  • Make sure that the Earth Leakage Circuit Breaker goes to the ‘OFF’ position.
  • Reset the Earth Leakage Circuit Breaker to the ‘ON’ position.
  • Finally, you can switch ‘ON’ the main power supply.

Limitations of Earth Leakage Circuit Breakers (ELCBs):

An Earth Leakage Circuit Breaker is not the surest way to remove all the risks of electric shocks. There are some practical limitations involved.

Like, an Earth Leakage Circuit Breaker alone will not detect overload conditions, phase-to-phase short circuits, or phase to neutral short circuits.

For these purposes, you will need a more modified and advanced form of circuit breakers – RCBOs!

RCBOs or Residual-Current Circuit Breakers with Overcurrent protection come in 1, 2, 3, and 4 pole configurations. And they have separate circuits to detect the imbalance current and overload situations.


They have the same interrupting mechanism.

An ELCB protects against electric shocks when current flows through a person’s body from a phase (live/line/hot) to Earth. But if the current flows through a person from phase-to-phase or phase to neutral path the device can’t distinguish between the current flow through an aimed load and a current flow through a person.


ELCBs offer great protection against leaking current faults. But it was due to some downsides and limitations that RCBs/ RCDs are known to be more effective.

The key takeaways from this thorough examination of ELCBs, their types, and operation are:

  • Any leakage of current is a potential danger to human lives and appliances. Therefore, the installation of an electrical safety device is a must.
  • Wisely chosen ELCBs are now the only way to ensure your electrical safety.
  • Voltage Operated ELCBs have become obsolete now. If you find any outdated ELCB installed, replace them with the RCBs (Current Operated ELCBs).
  • Perform an annual checkup of your electrical safety gadgets like ELCBs.

I hope you find the information interesting and useful.

Have any questions? Feel free to leave me a comment below.


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