Wrenches:
I came across this U-tube video that I think is relevant: https://www.youtube.com/shorts/Lyfdr1AWzU4 A factor that aggravates the arc producing and sustaining characteristics of solar circuits is the nature of the IV curve. One can short solar circuits and create a zero volts situation. Once that short first opens, the voltage climbs quickly, sustaining the arc even more than the video demonstrates. I think we all need to remember this concept when considering our designs and installations. It seems to me that the fiery RSD failures that have been described here are more than likely due to the RSD devices opening PV circuits under load. This is like disconnecting MC connectors under load. An arc will be created and is likely to sustain for some time. If we could contrive systems that removed the load from PV circuits just prior to RSD activation this problem might be resolved. It may not be that difficult to achieve this. In theory, if the RSS system first disconnected the AC feeder to the inverter and then after a short delay the RSS activated, the RSS devices would not be opening under load. In its most crude form a contactor on the AC circuit would be opened by the RSS initiation device and then shortly thereafter the PV RSDs could open without arcing. I have often thought that PV inverters should have an “inhibit” circuit that, with the opening of a low voltage contact, the inverter would shut down. Many power electronics have this feature. FXR inverters have this. The inhibit function could be used to take the load off of PV circuits prior to rapid shut down. Also, the inhibit function could be used to protect batteries in AC coupled systems without the need for high amperage AC contactors. William Miller Miller Solar 17395 Oak Road, Atascadero, CA 93422 805-438-5600 www.millersolar.com CA Lic. 773985
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