# Re: [PSES] High Touch Current and GFCIs

The cancellation that Mr. Woodgate points out could occur with industrial
equipment that was powered from North American  120/240 V ac, 3-wire single
phase or 240 Vac, single phase circuits (where there are two line conductors
separated in phase by 180 degrees on a center-tapped, single-phase distribution
transformer) or from 208 Vac, single-phase equipment  (where the two line
conductors are separated in phase by 120 degrees on a 3-phase distribution
transformer).

If your market was strictly North America, you might use this to your
advantage.  It is likely, though, that such equipment is sold on the global
market, so you might test for touch current with a 230 V, single phase input
(that is, 230V to earthed neutral).  Then, no such cancellation of touch
current.

Best regards,

Don Gies

Internal
From: John Woodgate <j...@woodjohn.uk>
Sent: Thursday, August 25, 2022 3:32 PM
To: EMC-PSTC@LISTSERV.IEEE.ORG
Subject: Re: [PSES] High Touch Current and GFCIs

[External email: Use caution with links and attachments]

________________________________

There is also a question in my mind as to whether there can be partial
cancellation of touch current. I suspect this is highly improbable in the US,
due to the distribution system ensuring that the neutral has a very low voltage
difference from the PEC. But in Europe, it's not inconceivable that the neutral
could be, say, 4.6 V relative to PEC and the neutral-to-PEC capacitance 25
times that of L to PEC, so that half the L-to-PEC leakage current is cancelled
by the N to PEC current.
======================================================================================
Best wishes John Woodgate OOO-Own Opinions Only
Rayleigh, Essex UK
It all depends

On 2022-08-25 19:12, Richard Nute wrote:

I wish to make two points:

1.  Kirchoff’s Current Law states that the sum of currents entering a node
equals the sum of currents leaving the node.  The Law applies to summation of
leakage (touch) currents (e.g., through a 2,000-ohm resistor) and to summation
of protective conductor currents (through 0 ohms).  In a power strip protective
grounding conductor, I’m assuming 0 ohms to ground, so the current is slightly
higher (1 to 10 % depending on the leakage current limit and the voltage you
are using) in the protective grounding conductor than leakage (touch) current.

See IEC 60990 for touch (leakage) current and protective conductor current
measurement procedures.

1.  A GFCI measures the current difference between line and neutral
conductors, not current in the protective conductor.  It nominally operates at
5 mA.  We assume (with a reasonable degree of accuracy) that leakage (touch)
current is 100% of the differential current measured by the GFCI.  It is
possible, although unlikely, for some of the GFCI differential current to find
another return path than the protective grounding conductor.
Best regards,
Rich

From: Lfresearch Jose
<000000734758d943-dmarc-requ...@listserv.ieee.org><mailto:000000734758d943-dmarc-requ...@listserv.ieee.org>
Sent: Wednesday, August 24, 2022 1:44 PM
To: EMC-PSTC@LISTSERV.IEEE.ORG<mailto:EMC-PSTC@LISTSERV.IEEE.ORG>
Subject: Re: [PSES] High Touch Current and GFCIs

I have wondered about something similar.

If I use a 6 way power strip, I’m assuming all the leakage currents for
anything plugged in sum. Is that correct? I recall getting a few trips when I
used a power strip and It’s only just twigged that might be why.

Cheers,

Derek.

On Aug 24, 2022, at 3:27 PM, Brian Kunde
<bkundew...@gmail.com<mailto:bkundew...@gmail.com>> wrote:
﻿
If I have a rake of electrical equipment with a single power cord and a
combined touch current exceeding 6mA, and I plug the rake into a circuit with a
GFCI, will it trip?

Thanks.

The Other Brian
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