Michael,
The arcing was between hot and neutral. GFCI outlets would have made no
difference.
- Robert -
Robert A. Macy, PEm...@california.com
408 286 3985 fx 408 297 9121
AJM International Electronics Consultants
619 North First St, San Jose, CA 95112
-Original Message-
From: michael.garret...@radisys.com
To: emc-p...@majordomo.ieee.org
Cc: Robert Macy
List-Post: emc-pstc@listserv.ieee.org
Date: Thursday, October 25, 2001 5:52 PM
Subject: 120V Ground Faults
>
>Robert,
>
>>From my experience, I think you will find that arcing ground faults are
>inherently high-resistance in nature and, while dramatic, do not
>necessarily pull significant amounts of current. Most 15 amp breakers will
>likely require several seconds/minutes to blow at 60/30 amps, which is what
>you'd get with a 2/4 ohm arc. In reality, I wouldn't be surprised to see
>something more like a 10-20 ohm figure being used for this type of
>phenomenon, which would allow a 15 amp breaker to arc virtually
>continuously (i.e. the home arc-welder). The fact that arcs are drawn -
>and sustained - at 120 volts is, I believe, relatively rare.
>
>Higher voltage systems (and GFCI outlets) have ground fault systems that
>rely on the detection of zero sequence (neutral leakage) currents. My
>understanding is that the decision to require this type of protection on
>480 volt systems over 1200 amps was largely due to the increased likelihood
>they'd be able to draw and sustain an arc, as well as the damage that can
>be caused at these higher power levels (balanced with the concerns of
>cost-effectiveness of installing them more broadly). I feel they drew the
>line in an appropriate place.
>
>In my experience, while problems, such as this, do arise, the frequency and
>relative damage caused by them is relatively small. I think you would have
>seen a change (like the addition of GFCI about 25 years ago) if the case
>were otherwise. You should be able to add zero sequence current sensing to
>your household panel, should you care to do so, for ~$500, but where
>out-of-the-box systems exist for 480 volt systems, this would need to be a
>custom design amploying the combination of a sensor relay and a shunt-trip
>breaker. Of course any nuisance trips you may experience similar to your
>GFCI would take down your main You can buy a LOT of GFCI breakers for
>these dollars. Caveat Emptor/Engineer.
>
>Regards,
>
>Michael Garretson
>Compliance Engineering Manager
>RadiSys Corporation
>+1 503 615-1227
>
>
>
>"Robert Macy"
> To: "Dan Kwok"
,
>Sent by: cc:
>owner-emc-pstc@majordom Subject: Re: skinny
power cords.
>o.ieee.org
>
>
>10/25/01 02:36 PM
>Please respond to
>"Robert Macy"
>
>
>
>
>
>
>
>It definitely was not supplied by the heater company. It was a high
>quality
>UL approved cord. It's just that this cord carbonized and burst into flame
>as the arc was existing. The flames did immediately extinguish when the
>arc
>was stopped by unplugging the cord which is good.
>
>But again, it was disturbing that the 15A breaker provided no protection.
>
>Anyway, it was a good lesson for this "sleeping" guy. Now I take
>electrical
>distribution inside my home much more seriously.
>
> - Robert -
>
> Robert A. Macy, PEm...@california.com
> 408 286 3985 fx 408 297 9121
> AJM International Electronics Consultants
> 619 North First St, San Jose, CA 95112
>
>-Original Message-
>From: Dan Kwok
>To: Robert Macy ; emc-p...@majordomo.ieee.org
>
>Date: Thursday, October 25, 2001 1:42 PM
>Subject: Re: skinny power cords.
>
>
>>
>>Hi Robert,
>>
>>Recently, I bought several similar heaters for my home. I recall reading
>in
>>the operation instructions, explicit safety warnings against using
>extension
>>cords with the heater. Was the extension cord supplied with the heater?
>>
>>
>>-
>>Dan Kwok, P.Eng.
>>Principal Engineer
>>Electromagnetic Compatibility
>>Intetron Consulting, Inc.
>>Ph (604) 432-9874
>>E-mail dk...@intetron.com
>>Internet http://www.intetron.com
>>
>>- Original Message -
>>From: "Robert Macy"
>>To: "Roman, Dan" ;
>>Sent: Thursday, Octobe
