Detection of ground faults [RE-wrenches]

[Drake Chamberlin - Electrical Energy]

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At 08:13 AM 01/14/2002 -0800, you wrote:
>On 1/12/02, Graham Owen wrote:
>>Does anyone know of a device available at this time that helps locate 
>>ground faults and
>>arc faults?

Why are all these wires getting nicked?  This is not normal.  Even in a 
Romex wired structure with hundreds of runs, it is rare to have even one 
wire get penetrated.  (When one does, it ain't good).

The best device to identify a shorted wire is a Digital Multi Meter.  Use 
the continuity function, and test between all the wires and a grounded 
object.   After testing between the hot, and both neutral and equipment 
ground,  take the wires loose at both ends of the run, and test between all 
of them and ground.

Also, you can test with a Megger or high voltage insulation tester.  This 
is good to find conditions that might trip an arc fault detector, but might 
not trip a breaker.  This condition could exist with an over driven staple.

If wires are routinely getting shorted in conduits, it means that the wires 
are being pulled in too stressful a manner.  Code requires us never to have 
more than 360 degrees of bend in a conduit run.  Never, ever jerk on a 
wire.  If it absolutely won't pull, drag it back out of the conduit and add 
more lube, or make a new head on the wires (where they hook on to the rope 
or fish tape).

I worked on a commercial job in Florida where certain crews had PVC conduit 
runs with 450 degrees of bend, pulling 500 kcmil wires through with power 
pullers.  Even these didn't short out, even though the stress on the 
insulation must have been great.

So, I'm a bit confused about all these ground faults.

Best,

Drake

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