Milo902
Member
- Location
- Charlottesville, VA
Now the monkey wrench. Up to this point, my calcs have been from the AC combiner panel to the interconnection point. If we stopped there then it's clear the 480V system is the winner. The next step is considering the inverter to combiner panel run. With the shape of the array, I have inverters from 150 to 500' away from the combiner panel.
The 60kW solectrias can accept up to a 2/0 conductor, maxing this out at 2/0 Cu yields a 0.4% VD at 150', 0.66% at 250' and 1.32% at 500'. Based on the previous post's analysis, the actual kWh loss for these runs shouldn't be a concern, but the voltage at the inverter terminals may.
If the whole plant is cranking, I can expect a 2.65% voltage rise at the 150' inverter, 2.91% at the 250' inverter, and 3.57% at the 500' inverter. I have traditionally tried to keep my AC voltage drop under 2% w/ the occasional stretch to 2.5%. Solectria specifies a maximum VD of 2% to the interconnect, and we have blown right past that. Keep in mind these percentages are calculated based on L-N voltages as the inverter is connected in a Wye config (based on their neutral connection). If I consider L-L voltages, the 500' inverter will see a 2.06% voltage rise. I plan to follow up w/ Solectria next week to get their input. If the interconnection voltage is running high, we may have unhappy inverters under these conditions.
Alternate ideas? How about a voltage regulator at the AC combiner panel to buck voltage? I'm not familiar with these in practice and not sure what the cost implications would be, but it could solve the voltage issue and even allow smaller cables ran to the interconnect. Does anyone have any experience with this approach?
The 60kW solectrias can accept up to a 2/0 conductor, maxing this out at 2/0 Cu yields a 0.4% VD at 150', 0.66% at 250' and 1.32% at 500'. Based on the previous post's analysis, the actual kWh loss for these runs shouldn't be a concern, but the voltage at the inverter terminals may.
If the whole plant is cranking, I can expect a 2.65% voltage rise at the 150' inverter, 2.91% at the 250' inverter, and 3.57% at the 500' inverter. I have traditionally tried to keep my AC voltage drop under 2% w/ the occasional stretch to 2.5%. Solectria specifies a maximum VD of 2% to the interconnect, and we have blown right past that. Keep in mind these percentages are calculated based on L-N voltages as the inverter is connected in a Wye config (based on their neutral connection). If I consider L-L voltages, the 500' inverter will see a 2.06% voltage rise. I plan to follow up w/ Solectria next week to get their input. If the interconnection voltage is running high, we may have unhappy inverters under these conditions.
Alternate ideas? How about a voltage regulator at the AC combiner panel to buck voltage? I'm not familiar with these in practice and not sure what the cost implications would be, but it could solve the voltage issue and even allow smaller cables ran to the interconnect. Does anyone have any experience with this approach?