What is Surge Current Capacity in RCCB or RCD?


surge current capacity in RCCB or RCD


If you are going to Purchase an RCCB or RCD, that time you will notice the term 'Surge Current Capacity' in its specification details. Some times we need to select an RCCB for purchase according to surge current capacity requirements. So, in this article, we are going to know what is Surge Current Capacity in an RCCB or RCD. RCCB stands for Residual Current Circuit Breaker and RCD stands for Residual Current Device. Both are almost the same devices.


What is Surge Current?


The high amount of excess current flowing in a circuit due to suddenly increase in voltage or voltage imbalance is called Surge Current.

In the below diagram you can see the sudden increase in voltage which causes the flow of surge current in an electrical circuit.

surge voltage or impulse voltage


Surge current generally flows in a circuit for a very short time duration, it may be a few seconds or milliseconds. The amplitude of a surge current flowing in a circuit maybe 10 to 15 times more than the amplitude of the normal current. Surge current occurs in a circuit, due to instant switching, voltage imbalance, equipment faults, suddenly increase in load, lightning, etc.

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Surge Current Capacity in RCCB or RCD


According to the IEC 61008 and IEC 61009 standards, RCDs should be able to withstand 200A ring wave impulse or surge current and RCDs classified as 'Selective' should be able to withstand 3000A surge current of the specified waveform.

Suppose an RCCB has surge current capacity 250A. That means that RCCB can withstand up to 250A surge current when any fault or voltage imbalance occurs.

It is must need to check the surge current capacity of an RCCB during the purchase which is to be used with induction motors, transformer circuits, capacitive loads, etc. Because during the starting of the induction motor surge current occurs. If you use a surge protector or suppressor, that will not able to prevent the surge current because surge protector is designed to suppress voltage not surge current.

So surge current capacity of an RCCB is very important because if the amplitude of the surge current or impulse current is below to the surge current capacity of the RCCB, it cannot causes any harm. Suppose in a circuit, a maximum 200A surge current flowing possible. For that circuit, that RCCB suitable which having surge current capacity 250A.


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What is Surge Current Capacity in RCCB or RCD? What is Surge Current Capacity in RCCB or RCD? Reviewed by ETechnoG on 12/31/2019 Rating: 5
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