What is Circuit Breaker?
A circuit breaker is one type of safety device used in an electrical system to restrict damage to electrical circuits by automatically breaking the current flow in case a fault occurs, such as overload or short circuit. It works as protection from overheating, fires, or other hazards caused by excessive stress on electrical circuits.
Here’s how it works:
- Overload Protection: When a circuit draws more than its rated current, it causes the circuit breaker to trip and becomes an open circuit, thereby avoiding overheating of wires and posing potential fires.
- Short Circuit Protection: If there is a short circuit-wires carrying electricity are close to one another so that they touch each other-the circuit breaker determines this and becomes an open circuit to avoid damaging the electrical supply from causing damage or fire.
- Manual Reset: After the fault is cleared, the circuit breaker can be manually reset and reused after tripping.
Circuit breakers are widely used in homes, businesses, and commercial and industrial systems due to their safe and reliable electrical operation. They can be found in various types in terms of thermal, magnetic, and combination due to a specific application or protection need.
What is an Earth Leakage Circuit Breaker (ELCB)?
An ELCB is a safety device in the electrical systems of a house, used to prevent possible electric shocks and fires caused by leakage currents. It detects differences between the live or hot wire and the neutral wire; should an imbalance occur, the ELCB automatically withdraws the electrical supply.
Here is the working technique:
Types of ELCBs
Voltage ELCB (Old Type):
The older type of ELCB operates based on the voltage difference between earth and neutral wire. Once leakage current travels through the earth side (for example, when there is faulty appliance), the ELCB senses the voltage difference and cuts off the circuit.
This is the less common type nowadays because it has limitations, such as its incapability of detecting leakage currents that do not produce a noticeable voltage difference.
Residual Current Device (RCD) or Residual Current Circuit Breaker
(RCCB) Modern Type:
A more commonly used type today, which relies on detecting residual current or imbalance on the live and neutral wires of the leakage that indicates current flows to the ground.
It cuts off the circuit within nanoseconds upon detecting leakage current-if any present, usually well above a predefined threshold-to avoid possible damage, such as electric shock or even fire.
RCDs or RCCBs are much more sensitive to leakage currents than the original voltage-type ELCBs and more so faster.
Working of Earth Leakage Circuit Breaker
The Earth Leakage Circuit Breaker (ELCB) detects electrical leakage or stray currents, which could lead to electric shock or fire hazards. Here’s how an Earth Leakage Circuit Breaker works; most especially the modern type, the Residual Current Device or RCCB works as follows:
1. Current Flow Under Normal Conditions:
Normally, under the circumstances, current flows along the live (hot) wire, passes through the electrical appliance, and back to the source via the neutral wire.
In a balanced system, the current that flows through the live and neutral wires is of the same magnitude in opposite direction. Current flowing out from the live wire is equal to the current flowing back into the neutral wire.
2. Leakage Detection
In case of leakage current, where a short-circuited appliance or wiring lets the current flow to earth or ground (through a human body), for instance, the current balance is disrupted.
The leakage might result from damaged wiring, defective appliances, or bad insulation whereby part of the electrical current would now be flowing to earth instead of returning back through the neutral wire.
3. How the ELCB Detects Leakage:
Core Balance Transformer: Inside the ELCB, a core balance transformer or differential current transformer is placed. This component watches the current balance between the live and neutral wires. Under normal circumstances, the current that should enter through the live wire must be equal to the current returning back through the neutral wire and no current can flow through the earth or ground.
Functions of Earth Leakage Circuit Breaker
The ELCB performs many significant functions in electrical safety, especially about preventing electric shocks and electrical fires due to leakage currents. Thus, the basic functions of an ELCB are as follows:
1. Protection Against Electric Shocks:
The main role of an ELCB is to sense leakage currents-small flows of the current to the ground that could flow because of a fault in the electrical system, such as a malfunctioning appliance or incorrectly wired appliance.
When the leakage current attains a dangerous value, which is predominantly greater than 30 mA that is capable of causing a fatal electric shock, then the ELCB operates by tripping the electrical supply and eliminating the chance of electrocution.
2. Protection Against Electrical Fire:
The leakage currents can also bring about overheating of wiring, appliances, or electrical elements, and may eventually trigger fires.
The ELCB thus detects and de-energises circuits with excess leakage to thereby prevent overheating and prevent what would otherwise have resulted from sustained leakage: electrical fires.
3. Detection of Ground Faults:
ELCBs can detect ground faults, wherein the current had to take an unintended path to reach the earth, for example, through human body or by damaged cables.
It compares the current flowing through the live and neutral wires. In case there is an imbalance caused by leakage, it sends a signal to trip the breaker and cut off the circuit.
4. Safety from Overheating in Humid or Wet Conditions:
ELCBs are especially designed for use in places where there could be presence of water or moisture (such as kitchen, bathroom, or outdoor installations), because leakage current is more likely to take place in those conditions.
An ELCB can automatically disconnect the supply in case leakage is detected, reducing its ability to cause electric shock in high-moisture environments.
Types of Earth Leakage Circuit Breaker
There are two general categories of Earth Leakage Circuit Breakers (ELCBs), both types of which are designed to offer protection from leakage currents, but they work in different manners. They consist of the following two types.
1. Voltage-Operated ELCB (Old Type)
Working:
The voltage-operated ELCB works through detecting a voltage difference between earth and neutral wire.
If there is any leakage current flowing through the earth (for example, because of a fault in an electrical appliance or installation), it causes a voltage difference between the neutral and earth.
This voltage difference is detected by the ELCB which then trips the circuit and disconnects the electrical supply.
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Disadvantages
In this type of ELCB, only that type of earth leakage can be detected where a noticeable voltage difference between the earth and neutral is developed.
It may not detect leakage currents which do not produce a measurable voltage difference or those that pass through unauthorized routes (such as leakage currents that directly flow to the ground without developing a voltage difference).
These shortcomings make the voltage-operated ELCBs less in number nowadays and mainly replaced by the more efficient residual current devices (RCDs).
Features:
Detects voltage imbalances.
Much less sensitive than modern types.
Older technology, largely phased out today.
Voltage Operated ELCB
| Feature | Voltage-Operated ELCB |
|---|---|
| Detection Mechanism | Detects voltage difference between earth (ground) and neutral wire. |
| Working Principle | Senses a voltage imbalance caused by leakage current flowing through the earth. |
| Tripping Mechanism | Trips when a voltage difference (typically caused by leakage) is detected between earth and neutral. |
| Sensitivity | Less sensitive compared to current-operated types. May not detect small leakage currents. |
| Threshold for Tripping | Triggers if the voltage difference between earth and neutral exceeds a preset value (usually around 30V or higher). |
| Response Time | Relatively slower in response compared to modern RCDs. |
| Type of Protection | Primarily provides protection against leakage current flowing to the earth (ground). |
| Common Applications | Older installations, now largely replaced by current-operated ELCBs. |
| Limitations | May fail to detect leakage currents that don’t cause a noticeable voltage difference or leakage directly into the ground. |
| Usage | Outdated in modern electrical systems, with RCDs (Residual Current Devices) now being more commonly used. |
| Reset Mechanism | Manual reset after tripping, once the fault is corrected. |
| Reliability | Less reliable than modern RCDs due to its inability to detect certain types of leakage. |
Current Operated ELCB/RCCB
| Feature | Current-Operated ELCB (RCCB) |
|---|---|
| Detection Mechanism | Detects imbalance in current between the live (hot) and neutral wires. |
| Working Principle | Senses the difference in current between the live and neutral conductors. If there is a leakage current (e.g., to the earth), this imbalance is detected, and the RCCB trips to disconnect the circuit. |
| Tripping Mechanism | Trips instantly when the residual current (imbalance between live and neutral) exceeds a set threshold, typically 30 mA or 100 mA. |
| Sensitivity | Highly sensitive, capable of detecting small leakage currents that could lead to electric shock or fire, typically around 30 mA (sensitive enough to protect human life). |
| Threshold for Tripping | Trips when the residual current exceeds a predefined value, commonly set at 30 mA for human safety (or higher values for industrial use). |
| Response Time | Very fast response time, typically within 30 milliseconds, ensuring immediate protection from electrical hazards. |
| Type of Protection | Protects against earth leakage currents that could cause electric shock or fire. Provides high safety, particularly in damp or wet areas (e.g., bathrooms, kitchens). |
| Common Applications | Widely used in residential, commercial, and industrial installations to prevent electric shocks and fires. |
| Limitations | Does not provide overload protection or short-circuit protection (for this, a Miniature Circuit Breaker (MCB) or RCBO is needed). |
| Usage | Commonly used in modern installations, replacing voltage-operated ELCBs due to its better reliability and faster response time. |
| Reset Mechanism | Can be manually reset after tripping, once the fault has been cleared. |
| Reliability | Highly reliable in detecting leakage currents and ensuring safety against electrocution or fires. |
| Enhanced Features | Often integrated with Miniature Circuit Breakers (MCBs) or Residual Current Breakers with Overload Protection (RCBO) for complete protection (overload, short-circuit, and leakage). |
Earth Leakage Circuit Breaker Vs MCB
| Feature | Earth Leakage Circuit Breaker (ELCB) | Miniature Circuit Breaker (MCB) |
| Resetting Mechanism | Can be reset manually after tripping | Can be reset manually after tripping |
| Purpose | Detects and interrupts earth leakage currents | Protects against overload and short circuit conditions |
| Sensitivity | Detects small leakage currents (typically 30 mA to 300 mA) | Detects high current levels (typically above rated current) |
| Feature | Earth Leakage Circuit Breaker (ELCB) | Miniature Circuit Breaker (MCB) |
| Disadvantages | May trip unnecessarily due to minor leakages or external voltages | Does not provide protection against earth leakage currents |
| Detection Mechanism | Monitors the balance between live and neutral wires | Monitors the current flow to detect overcurrent or short circuit |
| Advantages | Provides additional protection against earth faults and electric shocks | Reliable protection against overcurrent and short circuits, easy to install and maintain |
| Primary Function | Provides protection from electric shock and fire hazards caused by leakage currents | Provides protection from excessive current that can cause overheating or fire |
| Tripping Time | Quick response to earth leakage currents | Quick response to overcurrent and short circuits |
| Applications | Residential, commercial, and industrial installations to protect against electric shock | Residential, commercial, and industrial installations to protect circuits from overload and short circuits |
| Typical Use Case | Used to protect against earth faults and leakages | Used to protect electrical circuits from overload and short circuits |
| Types | Voltage Operated ELCB (VOELCB), Residual Current Circuit Breaker (RCCB) | Single-pole, double-pole, triple-pole, and four-pole MCBs |
Frequently Asked Questions (FAQs)
- What is an ELCB?
An ELCB (Earth Leakage Circuit Breaker) is a safety device that detects leakage currents and disconnects the power to prevent electric shocks or fires. - How does an ELCB work?
It detects an imbalance in the current between the live and neutral wires, triggering the circuit to trip when a leakage is detected. - What are the types of ELCB?
The two main types are Voltage-Operated ELCB and Current-Operated ELCB (commonly known as Residual Current Devices, or RCDs). - Why is an ELCB important?
It protects against electric shocks and fires by detecting and disconnecting leakage currents that can pose a hazard. - Where is an ELCB used?
It is commonly used in residential, commercial, and industrial electrical installations, especially in damp or high-risk areas like bathrooms and kitchens.
