[RE-wrenches] Safely inducing arc fault and ground fault in a completed array

[Exeltech]

Carl,

#1:  Under the conditions described by Larry below .. if by some chance the resistor somehow completes a circuit, you'll have up to 10 milliamps flowing through a 40K resistor, and in that case .. up to 4 watts dissipated.  To be on the safe side, use a 10W rated resistor just in case there IS a completed circuit.  If the array voltage is 500Vdc, use a 50K resistor.  If it's 600V .. a 60K  ... and so forth.

Of greater importance is to ensure you use a resistor that's specified for the rated voltage.  Most people aren't aware that resistors have a voltage rating.  To be on the safe side, make sure the one you use for this task is rated for 2X the anticipated voltage you'll encounter.

#2:
Arc faults occur in a variety of forms.  Larry did a good job describing them below.  They can be manually created with varying degrees of difficulty.

One fault to try to create (and the easiest of the list) would be the series fault.  Separate a conductor (or connection) between two PV while the system is under load.  I recommend using a matched pair of PV connectors with conductors attached, insert them between two PV, and use the conductors themselves as your "break" point (as opposed to using the existing connectors already on the PV).  Separating PV connectors under load will damage the pins and render the connectors unusable if the metal melts (and it could).

Be careful!

Dan




--------------------------------------------
On Mon, 11/25/13, Larry Crutcher, Starlight Solar Power Systems <larry at starlightsolar.com> wrote:

Subject: Re: [RE-wrenches] Safely inducing arc fault and ground fault in a completed array
To: "RE-wrenches" <re-wrenches at lists.re-wrenches.org>
Date: Monday, November 25, 2013, 3:55 PM
 
 Carl,

Assuming about 400 volts, a 40k ohm resistor from PV negative to ground should trip the ground fault. Solder up to some test leads, insulate the resistor and make the short. You'll only be conducting about 2 Watts through the resistor. Arc fault, on the other hand, can be very complex. Series, parallel, inter string and more, pulsed, constant, varying intensity…..it get's beyond my understanding quickly. I'll bow out here and defer to others that are far more educated.

Larry
 
 
On Nov 25, 2013, at 2:04 PM, Carl Adams <swingjunkie at gmail.com> wrote:

Wrenches,

We just completed an install with the SMA STP12000TL-US.  I would like to induce two fault conditions into the system 1) ground fault, and 2) arc fault, in a manner that is both safe to equipment and personnel, in order to see how these units respond to those conditions, and in particular how the arc fault is cleared, after detection. (assuming it is detected)
 
Any suggestions appreciated.

With Regards
Carl Adams  NABCEP 031508-1SunRock Solar