The full form of ELCB is an Earth Leakage Circuit breaker.
ELCB is an 'on-load low-voltage circuit breaker'. It is an important safety device in the substation. ELCB acts as a circuit breaker. The other name for this device is called a Ground-fault circuit interrupter.
Purpose Of ELCB
This device protects electrical equipment and living thing from the ground fault. Current leakage in the earth leads to shock or damage to the person or electrical equipment.
Whenever the ELCB senses the differentiation in the current between the earth and the neutral wire then it stops the flow of electric current in a circuit. This ELCB prevents electric shock and fire.
History of ELCB
In the 1908s in Europe, the 220 V Voltage system is increasing in the home. Ground fault and it leads the circuit to fire. They invented ELCB to avoid this kind of fault.
At the initial stage, ELCB's function as the voltage-operated type and its protection range was small. This ELCB provides low sensitivity and a nuisance trip and it cannot detect current leaving live-wire.
To overcome this drawback, they invented differential current-operated type ELCB which provides high sensitivity and an accurate trip to the leakage current in the earthing system. It did not use an earth wire to detect a fault, it just uses a phase and neutral wire connection to detect a fault.
At the time of the invention, the names for both Voltage-operated type ELCB and current-operated type ELCB are referred to as ELCB. This common name brought confusion to the electrical industry and marketers. To avoid this confusion, the name IEC of the current-operated type ELCB was changed to RCCB/RCD.
- Full form of RCCB- Residual current circuit breaker
- Full form of RCD- Residual current device
In 1912, the Voltage-Operated ELCB was developed in Germany.
In 1950, they started the mass production of ELCB.
In 1965, they increased the sensitivity to 30mA. In the olden days, Japan and the USA used ELCB to prevent firing in the circuit due to ground fault.
Types of ELCB based on its operations
We can divide ELCB into two, based on its operation
- Voltage operating device
- Current operating device
Voltage operating device. (VOELCB)
The full form of VOELCB is a voltage-operating earth leakage circuit breaker.
In modern days, VO ELCB is not in use. Voltage operating ELCB always monitors the voltage of the circuit. If the device detects any faulty voltage on the metal enclosure of electrical equipment, then it automatically trips the switching mechanism of the circuit breaker and stops the flow of electric current.
Voltage-operated ELCB comprises only two major components, one is a circuit breaker and another relay.
Working principle of the current operating device. (RCCB)
The full form of RCCB is the Residual current operating device. RCCB (Residual current circuit breaker) is the other name for the current operating ELCB
The working principle of the Residual Current Circuit Breaker isKirchoff's current law
Kirchoff's Current law states that the "algebraic sum of the currents entering a node is equal to the algebraic sum of the current leaving node."
If the current entering the device is not equal to the leaving current then it automatically trips.
RCCB monitors the operating current of the circuit. If RCCB detects the faulty current, it trips the circuit.
ELCB comprises the following components that are contacts, a test button, an electromagnetic relay, and a sensing coil, a core balance-current transformer, a test button.
ELCB comprises the following components that are contacts, a test button, an electromagnetic relay, and a sensing coil, a core balance-current transformer, a test button.
Advantage
- Because of the core balance current transformer, it is more accurate to detect and trips the circuit.
- Available for single-phase and also for three-phase.
- This is more sensitive to a fault and the rated current is high.
- Because of the core balance current transformer, it is more accurate to detect and trips the circuit.
- Available for single-phase and also for three-phase.
- This is more sensitive to a fault and the rated current is high.
Operation of RCCB
We can explain the operation of ELCB in two cases.Normal operation (No differentiation in the entering and leaving current)
- In the first case, ELCB works fine and allows the current to flow in the conductor.
- In the first case, according to Kirchhoff's current law, the current entering through the phase is always equal to the current leaving the load from the neutral. In this condition, ELCB allows current without any disturbance.
Up-normal operation (differentiation in the entering and leaving current)
- When somebody gets an electric shock then, RCCB detects the differential current in the circuit and stops the flow of the electric current by breaking the conductor with the help of the switching mechanism.
- In the second case, if there is a leakage current in the line conductor then the fault current flows through the earth conductor.
- So there will be a difference in the current magnitude. This differential current induces a flux in the core balance of the current transformer. Core Balance Current Transformer induces flux according to the fault current.
The electromagnetic Relay is connected to the Core-Balance Current Transformer senses this induced flux and signals the circuit breaker and the switch mechanism of the circuit breaker stops the flow of current by tripping the lever of RCCB.
- In the first case, ELCB works fine and allows the current to flow in the conductor.
- In the first case, according to Kirchhoff's current law, the current entering through the phase is always equal to the current leaving the load from the neutral. In this condition, ELCB allows current without any disturbance.
- When somebody gets an electric shock then, RCCB detects the differential current in the circuit and stops the flow of the electric current by breaking the conductor with the help of the switching mechanism.
- In the second case, if there is a leakage current in the line conductor then the fault current flows through the earth conductor.
- So there will be a difference in the current magnitude. This differential current induces a flux in the core balance of the current transformer. Core Balance Current Transformer induces flux according to the fault current.
Operation VOELCB
In normal operating condition, the VOELCB works fine and allow current to flow through the conductor.
But, in faulty conditions, extra voltage tries to flow through the earth line and make a voltage difference. This extra voltage energizes the contacts of the electromagnetic relay due to the flow of voltage between the load and earth conductor then it trips the circuit and stops the flow of electric current.
One end of the relay coil is connected to the load and another end is connected to the earth leakage circuit breaker, it always senses the voltage of the electrical equipment.
Advantage
- Sensitive to a fault condition
- Whenever extra current and voltage flow through the ground line then the ELCB trips
- low cost simple in design
Disadvantage
- ELCB produces extra resistance and causes more damage to the earth's system
- The external voltage connected with the earth system leads to an unwanted trip
- High voltage electrically leaky appliances such as air conditioners, fridges, and a water heater may lead the ELCB to an unwanted trip.
- The voltage-operated ELCB is not so accurate to detect the fault. If ELCB senses the extra voltage, then the rated voltage automatically stops the flow of electric current