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Types of RCD - Residual Current Devices

May. 06, 2022

RCD - Residual Current Device - is the generic term for all types of residual current operating devices and is defined as: a mechanical switching device or combination of devices designed to break the contacts when the residual current reaches a given value under specified conditions. BAOKEZHEN introduces you to the more common types.



A mechanical switching device designed to switch on, carry and break currents under normal operating conditions and to break the contacts when the residual current reaches a given value under specified conditions. Depending on the age of these devices, they will conform to BS EN 61008 or BS 4293.



A residual current operated circuit breaker designed to perform protection functions against earth fault currents, overloads and short circuits. These devices comply with BS EN 61009. "Appendix G" of this standard also includes the RCD add-on module for BS EN 60898 circuit breakers.


Types of RCD - Residual Current Devices

Fused Spur Unit Metal Clad Switched 0130FMG



A type of circuit breaker providing overcurrent protection in combination with residual current protection, either as a whole or in combination with a residual current unit, which can be factory installed or installed on site.



A socket for fixed installation which incorporates an integrated sensing circuit which will cause the switch contacts in the circuit to open automatically at a predetermined residual current value. These will comply with BS 7288: 1990.


Earth Fault Relay

A device incorporating a detection of earth fault current, comparing its value with the earth fault current operating value and signalling to the relevant switching device to break the protected circuit if the earth fault current exceeds this value. The relay can be connected directly or fed from a separate toroidal coil.


Types of RCD - Residual Current Devices

Australia Twin RCD Plastic Socket with Switch SAA BKZ0230SPWA

The technology behind RCD

There are two available technologies for residual current devices, electromagnetic and electronic, both of which offer very reliable performance. Electromagnetic devices use a very sensitive toroidal coil which operates a trip relay when it detects a very small residual current. These devices usually do not require a reference earth wire and are unaffected by temporary power failures as the power to trip the device comes directly from the fault current.
These devices should be disconnected when performing insulation resistance tests to prevent damage to the equipment and to avoid incorrect test results.


Please contact BAOKEZHEN to get the RCD you want, we have different series and country types, we'll be happy to serve you.



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