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RCD's and similar protection

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phased confused

on 28 July 2014

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Transcript of RCD's and similar protection

RCD's and similar protection
- residual current device

- residual current circuit breaker

- ground-fault current interrupter
(American version of an RCD)

- Appliance leakage current interrupter
(Canadian version of American GFCI)

- residual current circuit breaker with overload protection

- core balanced earth leakage circuit breaker

Names of RCD devices
Single Phase operation
3 Phase operation
3 Phase RCD's operate by the same principal as single phase

But in this case an imbalance can be created by a phase to earth fault or a phase to phase fault.

The rcd will operate and open all phase and neutral conductors
Detects imbalances between phase and neutral

When there is a fault to earth, less current flows in the neutral

This creates a magnetic imbalance in the core, this is detected by the trip coil which opens the circuit

Tripping Times
Rcd's used for personal protection in NZ require their operation to verified as:

rated residual current
the device will operate within

5 times the rated current
the device will operate within

1.4 times the rated current for pulsating DC
the device will operate within

7 times the rated residual current for pulsating DC
the device will operate within
RCDs should be tested with a RCD tester to ensure they operate within the specified time for the class type

If a manual test button is present, that should be tested as well. If on a portable device then every time it is used.

If an RCD does not operate properly then it shall be discarded
how not to test an RCD
correct way to test RCd's
Full transcript