Minimum Import Relays for Solar PV Systems

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Solar Jake

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Project Manager
What is the most economical solution for an MIR on a solar PV system? The local utility requires these within their network, but the cost of installing one is sometimes more than the cost of the PV system being put on the building. Has anyone come across an economical solution?
 
These systems are typically 3 phase 208V. PV systems are typically backfeeding 15A or less. Utility might accept a PCS if the PCS can be set to zero export when consumption is north of zero, maybe 3KVA. I know there is some economical zero export equipment but utility requires minimum import relay to kick in at KVA specified by utility engineers at each project.
 
Solar Jake said:
These systems are typically 3 phase 208V. PV systems are typically backfeeding 15A or less. Utility might accept a PCS if the PCS can be set to zero export when consumption is north of zero, maybe 3KVA. I know there is some economical zero export equipment but utility requires minimum import relay to kick in at KVA specified by utility engineers at each project.
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Yeah, we have a PV system on a downtown network where the export of a single kW AC will trip three protection relays and shut down power to an entire high rise condominium building. We had to put in three levels of protection to ensure that it would never happen even though the output of our system is a fart in a hurricane compared to the building's usage. What a PITA; I hope to never see another one like it.
 
Pretty much the same situation here. Some of these system are 4 mods or 7 mods, on an 8 story apartment building.
ggunn said:
Yeah, we have a PV system on a downtown network where the export of a single kW AC will trip three protection relays and shut down power to an entire high rise condominium building. We had to put in three levels of protection to ensure that it would never happen even though the output of our system is a fart in a hurricane compared to the building's usage. What a PITA; I hope to never see another one like it.
Click to expand...
 
The problem with relays is that the utility wants utility-grade equipment. So it does not matter if you can find a cheaper way of doing it, if it's not utility-grade (expensive) then they won't approve it. Sometimes they want two for redundancy.
 
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