An RCD, or Residual Current Device is designed to detect an imbalance condition between the active and neutral conductors, indicating a fault with the potential for electrocution. If an imbalance is detected that is greater than the rating of the RCD it will cut power within milliseconds, preventing a fatal electric shock in the vast majority of cases.
Testing of RCD's, both fixed and portable is critical to ensure that it both trips when it should and does so in an acceptable time-frame to minimise the potential for electrocution.
RCD's are classified in AS/NZS 3190 as follows:
- Type I: 10mA
- Type II: 10mA to 30mA
- Type I RCD's are predominantly used in the medical industry and have a trip time of <40ms to be compliant.
- Type II RCD's are used in general industry and residential environments and requires a trip time of <300ms to be compliant.
How is the RCD tested?
We use the Metrel DeltaPat to test the RCD, both Type I and Type II RCD's to Australian Standard AS/NZS 3760:2010 compliance.
The following tests are conducted:
- Manual Trip Test;
- 50% RCD rating to identify nuisance tripping (this is over and above AS/NZS 3760 requirements);
- 100% RCD Rating;
- 500% RCD Rating.
All above powered trip tests are conducted at 0 degrees and 180 degrees.
Note: if a portable RCD is being tested a transformer is placed between the appliance and fixed power socket to ensure that the fixed RCD does not trip before the portable RCD.
All results are documented and held within the distribution board for fixed RCD's or with a site representative in the case of portable RCD's. A copy is also held by us as a backup.