Hi Vincent, Here <https://library.e.abb.com/public/c4e584f06cc6c4fbc1257ad800496193/2CSC420004B0201_RCDs%20EN.pdf> is a technical guide from ABB that you may find helpful. With regard to the 30mA trip level for an RCD, the paper refers to IEC 60479-1 and reproduces a Figure from that standard on page 2 relating effects on the body from exposure to ac currents (15 Hz to 100 Hz) with different durations. I don't believe the paper explains this, but this graph is specific to a left hand to feet current path through the body. The version of the standard that I have actually has a figure that is slightly different from the ABB paper, FYI.
The paper seems to indicate that the 30mA level was chosen since it marks the delineation between regions made by the c1 curve. Referring to the table on the next page (the table from the standard has more information), although below that current level let-go can occur it does not mention danger of ventricular fibrillation. If the assumption regarding the reason for this choice is correct, it appears that the IEC chose ventricular fibrillation as the major consideration, likely also considering that 30mA is still within zone 2 (AC-2 in the standard) for durations up to about 200ms and that people will generally react to move away from contact. As John mentions, likelihood of nuisance tripping was also surely taken into account when choosing this level. It appears that the UL standard focused on prevention of effects at a less severe level. Note that 5mA is always within zone 2 (AC-2) regardless of duration. That being said, I am not familiar with the history of the development of the relevant standards. If there are folks on this forum who are, I would love to see a more accurate or more detailed explanation. On Thu, Feb 16, 2017 at 12:49 AM, John Woodgate <[email protected]> wrote: > 1. That's a really big question and the really big answer is too big for a > mailing list. Search on the web for descriptions and/or comparisons. > > > > 2. The IEC standard is an international agreement. I suppose the GFCI is a > US-only (or NA-only) specification. Fault currents are obviously half with > 120 V supplies versus 230 V supplies. At 230 V, 5 mA would cause nuisance > tripping and problems with protective conductor currents due to capacitance > from L to PEC. > > > > 3. ELCBs required a PEC connection, so if the PEC is broken, the > protection does not work. RCCBs detect the difference between L and N > currents and do not use a PEC connection. > > > > With best wishes DESIGN IT IN! OOO – Own Opinions Only > > www.jmwa.demon.co.uk J M Woodgate and Associates Rayleigh England > > > > Sylvae in aeternum manent. > > > > *From:* Vincent Lee [mailto:[email protected]] > *Sent:* Thursday, February 16, 2017 3:04 AM > *To:* [email protected] > *Subject:* [PSES] Questions on RCB, RCCB and ELCBs > > > > > > Hi all, > > > > I am Vincent, newbies in Product Safety. Hence, I sincerely hope to seek > your professional answers to my following questions, > > > > 1) What are the major differences between RCB, RCCB, GFCI and GFEP ? > > > > 2) If the human-let-go-current-threshold is about 10mA, why does IEC 61008 > RCCBs used in Household being specified at 30mA trip current while GFCI > used in Household are specified at 5mA (+/- 1mA) ? > > > > 3) I heard that Residual Current Circuit Breaker are replacing Electrical > Leakage Circuit Breaker, in what ways are RCCB better than ELCB for > electrical safety protection that causes ELCB being replaced? > > > > Regards, > > Vincent > > - > ---------------------------------------------------------------- > > This message is from the IEEE Product Safety Engineering Society emc-pstc > discussion list. 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To post a message to the list, send your e-mail to <[email protected]> All emc-pstc postings are archived and searchable on the web at: http://www.ieee-pses.org/emc-pstc.html Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), large files, etc. Website: http://www.ieee-pses.org/ Instructions: http://www.ieee-pses.org/list.html (including how to unsubscribe) List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas <[email protected]> Mike Cantwell <[email protected]> For policy questions, send mail to: Jim Bacher: <[email protected]> David Heald: <[email protected]>
