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ELCB: Working principle, Full name and Circuit diagram

What is ELCB

An ELCB is one kind of safety device used for installing an electrical device with high earth impedance to avoid shock. These devices identify small stray voltages of the electrical device on the metal enclosures and intrude the circuit if a dangerous voltage is identified. The main purpose of Earth leakage circuit breaker (ELCB) is to stop damage to humans & animals due to electric shock.

Introduction

An Earth Leakage Circuit Breaker (ELCB) is a device used to directly detect currents leaking to earth from an installation and cut the power and mainly used in TT earthing systems.

For the protection of human body from the electric shock protective device like fuse or MCB are used. But generally this device are incapable of measuring small current flowing in human body, so requirement is to have a device which can sense small current and cut-off the supply instantly.

The device used for this purpose is known as Earth Leakage Circuit Breaker (ELCB).

An ELCB is a specific type of latching relay that has a structure’s incoming mains power associated through its switching contacts so that the circuit breaker detaches the power in an unsafe condition.

The ELCB notices fault currents of human or animal to the earth wire in the connection it guards. If ample voltage seems across the ELCB’s sense coil, it will turn off the power, and remain off until manually rearrange. A voltage sensing ELCB doesn’t detect fault currents from human or animal to the earth.

Types of ELCB

There are two types of ELCBs:

  1. Voltage Earth Leakage Circuit Breaker (Voltage-ELCB)

2.Current Earth Leakage Circuit Breaker (Current-ELCB).

Circuit Diagram of ELCB

ELCB-Earth Leakage Circuit Breaker circuit diagram

Working Principle of ELCB

It is current operated device designed to operate when a leakage current exceeds the predefined value.

It consists of a operating coil and a trip mechanism which operated the circuit when required.

The coil is supplied through 1-Ф supply so current in phase & neutral wire will be same.

This current will produce flux linkages same in magnitude but of opposite direction. This will result zero net flux in tripping coil of relay.

When fault or leakage current exceeds the limit higher current will flow in phase conductor than neutral current.

Resultant flux now is out of balance in tripping coil of relay. Difference of flux will induce emf in the coil which opens the contact of ELCB and isolate the circuit from the supply.

Voltage operated ELCB (VO-ELCB)

A VO-ELCB is designed to detect voltage imbalances between the live (phase) and neutral conductors in an electrical circuit. It primarily detects leakage currents that flow to the ground through an unintended path, such as through a person or through insulation faults in appliances or wiring.

VO-ELCBs operate based on the principle of comparing the incoming current (live conductor) with the outgoing current (neutral conductor). Under normal conditions, the currents in both conductors should be equal (balanced). If there is an imbalance, it indicates that some current is leaking to ground.This imbalance typically occurs when there is an earth fault, such as a person coming into contact with a live part or insulation breakdown in electrical equipment.

When a leakage current is detected by the VO-ELCB, indicating an earth fault, the device quickly trips (disconnects) the circuit. This action prevents the continuation of the fault current and helps to protect against electric shock hazards.

VO-ELCBs are designed to trip within milliseconds upon detecting a fault, ensuring rapid disconnection of power to minimize the risk of injury or damage.

Current Operated ELCB (CO-ELCB)

A CO-ELCB is designed to detect leakage currents directly through the grounding (earthing) conductor of an electrical circuit. It operates based on the principle of measuring the difference between the current flowing in the live (phase) conductor and the neutral conductor.

CO-ELCBs have a core which surrounds the live and neutral conductors along with the earth conductor. Under normal operating conditions, the magnetic fields generated by the currents in the live and neutral conductors cancel each other out in the core, resulting in no net flux. If there is a leakage current due to an earth fault, this balance is disturbed, and a residual current flows through the core of the CO-ELCB.

This residual current induces a magnetic field in the core, causing it to trip (actuate) the breaker mechanism. This action disconnects the electrical circuit almost instantaneously, preventing further flow of current that could cause harm.

When a fault occurs, the CO-ELCB detects the residual current flowing through the earth conductor. This detection triggers the breaker to trip, cutting off the electricity supply to the circuit.

CO-ELCBs are designed to operate quickly, typically tripping within milliseconds upon detecting a fault, thus minimizing the risk of electric shock to individuals and preventing damage to equipment.

Frequently Asked Question

What is an ELCB (Earth Leakage Circuit Breaker)?

An ELCB, also known as a Ground Fault Circuit Interrupter (GFCI) in some regions, is a device used to detect stray currents from an electrical circuit to the ground. It trips the circuit if it detects a leakage current, which could pose a risk of electric shock or fire.

Why are ELCBs used?

ELCBs are used to enhance electrical safety by quickly disconnecting a circuit when leakage to ground exceeds a preset threshold. This helps prevent electric shocks and reduces the risk of electrical fires caused by faulty appliances or wiring.

How does an ELCB work?

ELCBs work on the principle of detecting a difference in current between the live and neutral conductors. When there is leakage current to ground (e.g., due to a fault or insulation breakdown), the ELCB detects this imbalance and trips the circuit, cutting off the electricity supply.

Where are ELCBs commonly used?

ELCBs are commonly used in residential, commercial, and industrial electrical installations. They are typically installed in circuits where there is a higher risk of electric shock, such as bathrooms, kitchens, outdoor areas, and near water sources.

Why are ELCBs necessary?

ELCBs are necessary to protect against electric shock hazards caused by faulty appliances, damaged wiring, or insulation breakdown. They detect even small leakage currents that could indicate a fault and disconnect the power to prevent injury or damage.

What are the types of ELCBs available?

There are primarily two types of ELCBs:

Voltage-Operated ELCB (VO-ELCB): Detects the imbalance between the incoming and outgoing currents through the live and neutral wires.

Current-Operated ELCB (CO-ELCB): Detects leakage current directly through the grounding conductor.

Are ELCBs and RCDs (Residual Current Devices) the same?

Yes, ELCBs and RCDs are essentially the same type of device. The term “RCD” is more commonly used in Europe and Australia, while “ELCB” is more common in other regions. They both detect leakage currents and provide electrical shock protection.

How often should ELCBs be tested?

ELCBs should be tested regularly to ensure they are functioning correctly. This can be done using the test button provided on the device itself. It’s recommended to test them at least once a month to ensure proper operation.

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