This data, indicated in the manufacturer’s technical tables, indicates the level of current protection offered by the RCDs. The sizes typically used in low voltage electrical distribution are 30mA and 300mA. Typically the 30mA
threshold is dedicated to the protection of people.
To explain the intervention thresholds, take the example of a 30mA RCD: this one will not trip only for leakage currents >30mA but in a threshold between 15mA and 30mA:
‐ for currents lower than 15mA the RCD will surely not trip
‐ in the threshold 15mA ÷ 30mA could trip
‐ for currents> 30mA it will trip instantaneously.
The central threshold (15mA ÷ 30mA) is a threshold with uncertain trip because the RCD, being an electromechanical device, cannot have a certain and fixed trip threshold.


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