Given the recent discussions about transformerless inverters, troubleshooting, misc voltages
Do we need some guidance from inverter manufacturers and others to evaluate BEFORE all this equipment is in? Electrical tests for metal roofs, etc? Erika Weliczko REpower Solutions cell: 216.402.4458 On Mar 28, 2014, at 3:41 PM, Corey Shalanski <[email protected]> wrote: > Fellow Wrenches, > > We recently commissioned a 220kW rooftop PV system and are having some > inverter malfunction issues. The system details are as follows: > - Inverters: Power One Aurora Trio-27.6 (x7) > - Modules: Stion STN-130 (x1690) > - Array: Strings of 14-16 modules each, 8 strings per combiner, 1 combiner > per MPPT input > > It has been less than two months since we commissioned the system, and we > have already seen five of the inverters malfunction. While troubleshooting > these issues the inverter manufacturer had me measure positive-to-ground and > negative-to-ground voltage readings. At the inverter level I measured > instantaneous voltages of 100-200V before seeing a bleedoff; at the string > level the voltages were 10-20V before bleedoff. > > The inverter manufacturer is concerned with the magnitude (~200V) of this > instantaneous voltage and also the delay in bleeding off to zero - after > about five seconds the voltage level was still approximately 50V (but still > dropping). The manufacturer is claiming that this residual voltage should > drop to zero much more rapidly AND the presence of such a delayed bleedoff > indicates significant "leakage" coming from the array.They are further > claiming that this leakage is responsible for the damage to the inverters. > They suggested using a megger to test insulation resistance throughout the > installation. > > My questions to the group: > - Is there any truth in the inverter manufacturer's claims? > - Do my field measurements seem out of range from what others are seeing with > ungrounded arrays? > > Thanks for any information you can provide. > -- > Corey Shalanski > Joule Energy > New Orleans, LA > ᐧ > _______________________________________________ > List sponsored by Home Power magazine > > List Address: [email protected] > > Change email address & settings: > http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org > > List-Archive: > http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org > > List rules & etiquette: > www.re-wrenches.org/etiquette.htm > > Check out participant bios: > www.members.re-wrenches.org >
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