What Is an RCCB? Structure, Functionality & Applications

BTB Electric

• News
• May 16, 2024
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When electricity leaks to equipment and individuals come into contact with it, it can cause electric shock, potentially leading to life-threatening hazards. The Residual Current Circuit Breaker (RCCB) was developed as a safety circuit-breaking device to prevent electrical leakage faults from occurring. BTB Electric will compile important information regarding this type of automatic protective device, including its construction, operating principle, and practical applications of RCCBs. Please refer to our upcoming article for more details!

Definition and Structure

RCCB (Residual Current Circuit Breaker) is a safety device designed to protect electrical systems from leakage current and prevent electric shocks, as a result, protecting people life. It’s commonly installed at the main input of residential or industrial power systems, typically within concealed conduit wiring for enhanced safety.

RCCBs are available in two main configurations:

• RCCB Single-phase, 2-pole: designed for 220 V electrical system, used in residential/commercial construction. This type has 1 pair of L – N poles corresponding to 1 phase wire and 1 neutral wire
• RCCB Three-phase, 4-pole: Designed with 4 pairs of poles including 3 pairs L – phase connection and 1 pair N – neutral connection. This type of RCCB is used in industrial and commercial works, belonging to 3-phase 380V electrical system.

Internally, the key component is the Residual Current Device (RCD). The phase and neutral conductors pass through a toroidal core, constructed the primary winding, while the secondary winding connects to a sensitive trip relay. When an imbalance (leakage) occurs, the relay instantly trips the circuit.

Besides, the surface of RCCBs also feature typically a TEST button (colored yellow, green or black) to verify leakage detection.

Working principle of RCCB

The operating principle of RCCB is to ensure that the input current is equal to the output current. This principle was first mentioned in 1955 by Charles Dalziel. As BTB Electric has informed, RCCB has a core balancing transformer with primary and secondary windings and a sensitive relay.

• In normal operation, the current intensity of the conductors is equal, the vector sum of the currents is 0 and no residual magnetic field is produced.
• When there is a leakage current, it will create an imbalance in the circuit, the total current vector is not zero, creating a magnetic field, transmitting a signal to the sensor relay. This part will immediately break the circuit and cause the RCCB to trip.

The tripping mechanism on the RCCB circuit breaker occurs when the detected residual current is within the range of 50 – 100% of the rated tripping current.

RCCBs from BTB Electric are capable of detecting residual currents from 10mA (electric shock threshold) to 300mA (power cut-off in case of fire).

Key Functions

Designed specifically for the function of detecting and interrupting leakage current in circuits, RCCB has the following outstanding features:

• Safety protection: RCCB is an automatic circuit breaker that quickly detects leakage current risks and protects users as much as possible. The induction relay in RCCB is very sensitive, quickly cuts off the power, preventing leakage current from spreading to the surface of electrical equipment and causing harm to users.
• Leakage current detection: The leakage current detection mechanism of RCCB is very sensitive, based on the principle of balance between phase wire and neutral wire. This mechanism is also the basis for developing RCBO circuit breaker – a more versatile type of leakage current circuit breaker.
• High reliability: Humid environments are ideal for leakage current to propagate and are also the best environment for RCCB to function with a greater than normal circuit breaking speed.
• Anti-theft: When detecting current difference due to phase reversal to steal electricity, RCCB will immediately cut off the circuit to ensure grid safety.

In addition, RCCB does not have overload and short circuit protection functions.

Applications

RCCBs are typically used alongside grounding systems and are available in sensitivity ratings: 10 mA, 30 mA, 100 mA, 300 mA, 500 mA, with greater sensitivity at lower values. On the other hand, the system with RCCB requires the line to be hidden in the wall to limit risks.

With 4 levels of current cut like that, RCCB is applied in:

• Civil and commercial works with leakage current level 10mA, 30mA.
• Backup protection cases such as fire, electrical explosion with leakage current level of 100mA.
• Industrial distribution cabinets with leakage current level of 300mA, 500mA with delay time of 50ms, 250ms,…

In addition, depending on the protection scale, the RCCB used has different leakage current interrupting levels. For example, large buildings need to use 100mA or 300mA, while families only need 10mA..

How is RCCB different from RCBO?

RCCB and RCBO are two electrical circuit breakers that are often confused because they both have the ability to detect leakage current and have an external design with many similarities.

However, with the following basic characteristics of RCCB and RCBO BTB Electric, you will easily distinguish between these two types of devices.

• RCCB only has the function of detecting residual current (or leakage current) in the circuit and breaking the circuit. On the outside of RCCB there is a Test button and only 1 single lever.
• RCBO has the function of detecting leakage current and detecting overload and short circuit current, it is a combination of MCB and RCCB. The exterior of RCBO is quite similar to MCB and has an additional Test button.

RCCB and RCBO cannot be replaced with each other because of different features. In addition, you can distinguish these two devices more accurately through the article comparing RCCB and RCBO from BTB Electric.

Comparison of RCCB and ELCB

RCCB and ELCB are quite easy to distinguish because the biggest common feature of these two types of circuit breakers is the leakage current detection feature. However, ELCB has an integrated grounding device so it will detect residual current through the grounding device or the environment. Meanwhile, RCCB detects residual current in the circuit. In humid environments, ELCB detects leakage current better than RCCB.

In terms of external design, because it is a combination of RCCB and MCCB, ELCB has a block design similar to MCCB and has an additional Test button. ELCB does not have a 2-pole or less type, while RCCB does. 

Notes when installing and using RCCB

Ideal conditions for installing RCCB circuit breaker are as follows:

• Install RCCB in series after MCB to ensure additional overload protection for the circuit.
• Ambient temperature from -5 degrees C to 55 degrees C, average daily temperature does not exceed 45 degrees C.
• Humidity ranges from 45 – 95%.
• Avoid rough wall areas that are prone to vibration or strong impact.
• Installation height not exceeding 2000m above sea level.
• Should not be used in environments with too much steam, oil vapor, dust, alkali, acid and other harmful agents to RCCB.
• Avoid installing in places with direct sunlight for many hours continuously.
• The equipment should be placed in a covered electrical panel to prevent dust, water and other harmful hazards from entering.

During the use of RCCB, you need to ensure:

• Test the anti-leakage feature with the test button periodically once a month.
• The wiring system, including load wires and phase wires to the RCCB, are all connected to the wall.
• RCCB and MCB assemblies can be replaced with RCBOs with corresponding specifications.

RCCB from BTB Electric is the market’s leading high-quality residual current circuit breaker, manufactured and tested to meet European standards IEC/EN 61008-1. We have a wide range of RCCBs from 10mA to 300mA, serving most of the needs of customers. BTB Electric ensures that the devices fully perform their functions of preventing leakage current, electric shock and fire, ensuring safety for users.

See more products from BTB Electric at: https://btb-electric.com/products/