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Select Protection Devices

K M Thilakarathne

There are 2 devices in the market as a  RCD or  RCCB are installed for electrical circuit SELECT PROTECTION DIVICEs  for earth leakage protection  - what is the difference of its and what is most suitable for the human protection device 

  • 0

    RCCB stands for Residual Current Circuit Breaker and may also be called RCB or RCD.
    RCD stands for Residual Current Device, while
    RCB stands for Residual Current Breaker. 

    Whatever you call it, the device  disconnects the circuit as soon as it detects a current leak, either  to the earth wire or  by direct contact from a live part to something or someone directly on the ground

    This protection is achieved by monitoring the current flow in the line(s) and neutral. In a healthy circuit, the current flow via the line equals the return flow in the neutral.

    However, this return flow may not be equal to the line(s) current flow in the event of any abnormalities. A residual current device will sense the imbalance and interrupt the circuit.

    For safety of life a threshold of  less than 30mA is considered as the requirement, higher values, like 300mA or 100mA or slower operations, can serve a protective function but may not be sensitive or fast enough to prevent an electrocution.

    Hope that helps
    Mike.

  • 0

    RCD = Residual Current Device - that's a generic term for any protective device that includes a residual current element.

    RCCB = Residual Current Circuit Breaker - a specific device that contain a residual current element only - it has no other protective elements, such as for overcurrent.

    then there are others, such as:

    RCBO = Residual Current Breaker with Overcurrent -  a device with both residual and overcurrent protection elements.

    and MCB = Miniature Circuit Breaker - a device with overcurrent but no residual current protection elements.

    So where there's a requirement for RCD protection it could be satisfied by either an RCCB or an RCBO for example (or perhaps an MCCB+residual trip).

    It gets a bit confusing because some suppliers (and occasionally common usage) label RCCBs as RCDs - which isn't entirely wrong since RCCBs technically are RCDs, but does muddy the water somewhat. It'll get muddier still as new device (e.g. AFDDs) come in which usually contain RCD elements too.

       - Andy.

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    For your purposes, RCD and RCCB are the same thing. Technically an RCD is anything which detects a residual current, while an RCCB is a combination of a detection device and a device which can switch off the current (circuit breaker) once detected. In practice anything in a domestic setting will be an RCCB - possibly incorporated with a device that detects overload or short circuits (an MCB) - which when combined, is referred to as an RCBO.

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