Nick, If the voltage bleeds away when you connect your meter, you're seeing a capacitive charge that accumulates by things like wind blowing across the module -- there's a voltage potential, but no real current there. If the voltage stops at a stable value (especially if the value is some multiple of module open circuit voltage) then you have a ground fault, and the value indicates how many modules in from the end of the string.
Happy T-day, everyone! Phil Undercuffler Conergy > > > ---------- Forwarded message ---------- > From: Nick Soleil <[email protected]> > To: RE-wrenches <[email protected]> > Date: Tue, 24 Nov 2009 20:06:42 -0800 (PST) > Subject: Re: [RE-wrenches] Megometers > Hello Wrenches: > I have read a few of the archives on this subject, and have a couple > questions. I have been testing arrays with an insulation tester, and have > found that some module types have more leakage than other modules. Bill > mentioned Amorphous being really bad. > I have found my less expensive tester to work for me, but read in > another post about the value of a .001 M ohm tester. Is that level of > accuracy need? > I was testing a Sanyo array today, and was told that ~20M ohms on the > series string to ground was not a problem. With the strings isolated, the > array conductors commonly have voltage readings of 260V+ to ground, but it > dissipates with the meter connected. Is this induced voltage caused by the > leakage current that the manufacturer called 'normal?' > > Nick Soleil > Project Manager > Advanced Alternative Energy Solutions, LLC > PO Box 657 > Petaluma, CA 94953 > Cell: 707-321-2937 > Office: 707-789-9537 > Fax: 707-769-9037 >
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