GFCI = Ground Fault Circuit Interrupter
RCD = Residual Current Device
In North America, GFCI’s typically are included in an outlet that is part of a
branch circuit. The GFCI may have a number of outlets downstream. Under
normal conditions, the residual leakage current in the downstream outlets and
equipment connected to them is not zero, and can be a significant portion of
the 5 mA (nominal) trip current. So, when a person gets across the
GFCI-protected branch circuit and causes a trip, the current through the body
is the difference between the residual leakage current and the 5 ma trip
current. So, in such cases, the body current can be much less than the 5 mA
trip current.
The same is the case for the 30 mA RCD in Europe. However, the RCD is
installed in the breaker panel for an entire branch circuit, not a portion of
the branch circuit. So, the residual leakage current is higher, maybe as much
as twice that of North America. And, the voltage, 230, is about twice, so the
leakage current due to the higher voltage is almost twice that of North
America. Using these numbers, the European trip equivalent to the 5 mA trip
would be about 20 mA or more. However, the RCD is rated at 30 mA, so when a
person gets across an RCD-protected circuit, the body current will be much less
than the 30 mA trip current.
Rich
From: Pete Perkins <00000061f3f32d0c-dmarc-requ...@listserv.ieee.org>
Sent: Thursday, February 3, 2022 1:58 PM
To: EMC-PSTC@LISTSERV.IEEE.ORG
Subject: Re: [PSES] Machinery Leakage Current
Mike, et al, Thanx for mentioning my name; by now you should be able to
tell the stories as we’ve talked thru these things before.
From my experience, protection is primarily needed for cord and
plug connected equipment where the earthing/grounding is not considered
reliable – which includes North America. Most such equipment is allowed to
have higher touch current under fault conditions, where the fault current
exceeds 5ma the GFCI provides the needed protection
Since GFCIs look for the ‘lost to ground current’, the
differential current in the power cord, they also work in circumstances where
the earth/ground doesn’t exist (a 2-wire installation) or where it should
exist but doesn’t. Many are installed in older 2-wire installations because of
this in the USA.
RCDs rated to trip at 30mA are working right at the c1
Ventricular Fibrillation level of IEC 60479-1 so should provide that protection
for most people.
Not sure if RCDs are tested or rated for catching performance
degradation in machines but you apparently have experience with that. It would
be nice to see a paper on that performance feature.
North American GFCIs are rated at 5mA which is the
letgo-immobilization limit specified in IEC 60479-1. (Yes, I know the
allowable range is not trip at 4mA but must trip at 6mA; the rated trip current
is still 5mA.) You can still disengage from the current at that level,
providing that level of protection.
Both North American GFCIs and Euro RCDs are not rated to deal
well with high frequency signals generated by Switch Mode Power Supplies and
Variable Speed Drives for motors. Lots of ‘nuisance tripping’ results. There
is an ongoing UL project to get a handle on this and get it fixed here in NA.
Yes, EV chargers are being provided with GFCIs at higher levels,
depending upon the installation/application parameters.
:>) br, Pete
Peter E Perkins, PE
Principal Product Safety & Regulatory Affairs Consultant
PO Box 1067
Albany, ORe 97321-0413
503/452-1201
IEEE Life Fellow
IEEE PSES 2020 Distinguished Lecturer
<http://www.researchgate.net/Peter%20Perkins> www.researchgate.net search my
name
<mailto:p.perk...@ieee.org> p.perk...@ieee.org
Entropy ain’t what it used to be
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