Tony,
You raised a very good discussion. I have also seen a few Japanese customer
specifications (and even some European customer specifications)with 30 mA GFCI,
usually with a 0.1 second trip time.
Based on my research, the 30 mA GFCI, 0.1 second is based on JIS C 8371
"Residual Current Operated Circuit Breaker".
Now, whether or not 30 mA GFCI would be considered to be suitable for personnel
protection depends a lot on who you speak with?
If you ask the compliance safety engineers in the U.S., they'd say "Nope, 30 mA
GFCIs are not for personnel protection, at least not per UL 943, which defines
shock hazard as "A shock hazard is considered to exist at a part of a
ground-fault circuit-interrupter if: A) There would be current of 6 mA or more
in a resistance of 500 ohms connected between the part in question and the
grounded supply conductor, and B) The device would not operate to open the
circuit to the 500-ohm resistor within the time allowed in paragraph 23.1.".
For the Japanese (and even some Europeans), 30 mA, 0.1 sec. Residual Current
Devices may very well be considered suitable for personnel protection because
the trip current and trip time fall within Zone 2 of IEC 479-1, "Usually no
harmful physiological effects".
Being trained under the U.S. philosophy, I probably will not admit publicly
that 30 mA GFCIs is adequate for personnel protection; although it is
comforting to know that if someone should expose themselves to a line to ground
condition, that the 30 mA, 0.1 sec. GFCI should technically trip before any
harmful physiological effect results, at least per IEC 479-1.
Disclaimer: Electric shock is a very tricky science, it is not only dependent
upon current and exposure time, but body impedance, frequency, location of body
exposure, etc.
Tin
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