RCCB Working Principle and Its Importance

RCCB working principle

Despite the fact that electricity is now a necessary component of our daily lives, it nevertheless has drawbacks that affect both human health and property. When it comes to fire and electrocution, the two most significant risks associated with electricity, you cannot afford to take any chances. One essential safety precaution is to employ a residual current circuit breaker, or RCCB, especially when protecting electrical circuits. You will find all the information you require to comprehend what RCCB is and the RCCB working principle, functions, and definitions in this article.

What is RCCB?

Before we discuss the details of the RCCB working principle, it is essential to understand what RCCB is and why we need this device.

RCCB, also commonly called the residual current circuit breaker, is an electric current sensing device. It can automatically measure the amount of current being dissipated and disconnect the circuit when there is a fault in the connected circuit or when the current tends to surpass the RCCB’s rated sensitivity.

RCCBs prove helpful, especially when there is a sudden earth fault. They offer protection from the risks of electric shocks or electrocution, and in some of the worst cases, there could also be fire. With the installation of an RCCB, the circuit trips immediately, which helps minimize the chances of electrocutions, fire, or even electric shocks.  

RCCB working principle

RCCB’s working principle is based explicitly on a law called Kirchoff’s law. This law states that the incoming current must always be equal to the outgoing current in a circuit. RCCB thus compared the difference between the values of neutral and live wires. Ideally, the current that is flowing to the circuit from the live wire should be the same as that which flows through the neutral wire. In case of a fault, the current from the neutral wire is reduced; the differential between the two is hence known as residual current. On spotting such a residual current, the RCCB is triggered, which leads to tripping off of the circuit.

A test circuit included with the RCCB device tends to ensure that the reliability of this device is tested. When the test button is pushed, the current starts to flow through the test circuit. Hence, it creates an imbalance in the neutral coil of the device. The RCCB then trips, and the supply is disconnected, which checks the reliability of the RCCB.

Types of RCCB

Based on the RCCB working principle and its sensitivity, there could be multiple types of RCCB. Here are a few different kinds of RCCB that are commonly available.

Type AC (Alternating Current)

This type of RCCB device is excellent for general applications. Type AC mainly responds to residual currents that form a sinusoidal waveform.

Type A

Type A RCCB devices offer additional protection against pulsating direct currents, making them suitable for environments where electronic equipment is commonly used.

Type B

Type B RCCB device is such that it provides protection against pulsating direct current and alternating current and hence has a more sensitive electronic circuit.

Type F (Selective AC/DC)

This type of RCCB device is designed so that both AC and DC residual currents are present and both can be regulated.

Type H (High Sensitivity)

This type offers explicitly increased sensitivity for enhanced protection, especially in critical environments.

Sensitivity of RCCB

A human being can generally sustain an electric shock of up to 30 mA. Up to 10 mA may evoke a prickling sensation, which could also lead to muscle contraction and respiratory paralysis at around 30 mA. RCCBs are hence designed to look for small changes in the flow of residual current. In cases where protection from fire is needed, RCCB can also track higher changes in residual current, which can go up to 300 mA.  

Benefits of RCCB

RCCBs provide critical benefits when they are used in electrical circuits. Apart from swiftly disconnecting the flow of current to reduce the impact, they also have various other benefits of RCCB, such as follows:

  1. Fire Prevention

One of RCCBs’ most significant advantages is their ability to quickly identify and disconnect malfunctioning circuits with leakage currents, averting electrical fires.

2. Electrical Safety

    RCCBs often minimize the possibility of electrical equipment-related accidents by promptly cutting the circuit when residual current is detected, offering sufficient protection against electric shocks.

    3. Compliance with standards

      The use of RCCB aligns with the safety standards set for electrical instruments and also meets all regulatory requirements, enhancing the overall safety of electrical systems, even in households.

      4. Versatility

        RCCB devices are versatile and can be used with various electrical systems. This protects in commercial, household, industrial, and residential settings.

        5. Equipment protection

          RCCBs tend to safeguard various electrical appliances and equipment by preventing damage mainly caused by faulty currents. This, in turn, also ensures the longevity of the equipment.

          6. Early detection

            RCCBs’ fast response to residual currents allows for early detection, which reduces potential electrical hazards and ensures a safe environment.

            7. Cost-effective

              An RCCB is much more cost-effective than other safety devices, such as isolation transformers or earth leakage relays. It also provides an efficient and reliable way to protect equipment and people from electrical mishaps at a very reasonable price.

              Maintenance of Residual Current Circuit Breakers

              RCCB devices require routine testing and maintenance, particularly to guarantee the security of tools, people, and property. Here are some pointers to ensure the gadget is operating correctly.

              Visual Inspection

              Regular visual inspection of RCCB devices is necessary to detect signs of damage or wear and tear. You also need to check for corrosion, cracks, or other possible signs of physical harm. Finally, check whether the connections are secure and tight.


              Regular cleaning of RCCB is also essential to remove any contaminants, dust, or dirt that may be present on it. Such contaminants could also hamper the device’s performance. You can use either a soft cloth or a soft brush to clean the device while making sure the components are not damaged.

              Trip Test

              Regular trip tests are also essential to check whether the RCCB is working correctly. A trip test is conducted by pressing the test button on the RCCB device and causing it to trip. This test checks whether it can detect and respond to a fault or overload.

               Earth Loop Impedance Test

              The earth loop impedance test helps determine the effectiveness of the earthing arrangement installed in the device. It also ensures that the installation is safe and that RCCB can easily detect any faulty currents.

               Residual Current Test

              The residual current test is conducted so that RCCB can detect and respond to a residual current. This test is quite essential to ensure that the device can provide the needed level of protection against any fire risks or electric shocks.


              How does RCCB detect leakage?

              An RCCB device detects the difference in current flowing between the phase and neutral wires. It trips in the event of an imbalance in the current to ensure no risks are created.

              Can RCCB work without earthing?

              Earthing is essential for passing all the current to the ground to prevent electrical harm. However, the RCCB can also work without an earthing, though it is always advised to provide one.

              What is the difference between a Residual current device and a circuit breaker?

              The time it takes to break the circuit is the primary distinction between the circuit breaker and the residual current device. In parallel, the circuit breaker requires around 1000 times higher leakage current to identify and interrupt the circuit, while the residual current device should halt 25 to 40 milliseconds before the shock occurs.

              What is RCCB and RCB?

              RCCB is also known as RCB, and its function is to disconnect the circuit as soon as it detects a current leak in an electrical system.

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