Randy said:
Maybe there is an online PG&E Standard you can find? Down here it is 168% loading of nameplate for 4 hours max in a 24 hour period....The other 20 hours must be below 90% to allow cooldown...
Hey Randy, thanks! Any info on what the load time is for 400% of nameplate?
Just being crude -168% is +68% for 4 hours. Doing a linear extrapolation, 400% is +300%, using the overload ratio to scale the time - 68% / 300% = 0.226, 0.226 * 4 hours = 0.9 hours = 54 minutes. That's assuming the fuse in the transformer doesn't trip. 54 minutes is optimistic, since the shorter the period is, the faster the transformer heats up locally compared to the heat dissipation through the case.
This also doesn't account for voltage droop at 400% load, which may well be excessive.
Waidy - get some more Coulomb stations that coordinate the load amongst each other.... We have to know your intended scenarios to come up with good answers.
I'm finding lots of neat studies, though none of them exactly address this situation.
Application of Distribution Transformer Thermal Life Models to Electrified Vehicle Charging Loads Using Monte-Carlo Method
http://www.nrel.gov/vehiclesandfuels/pdfs/48827.pdf" onclick="window.open(this.href);return false;
Peak loads in excess of 140% of design capacity or extended periods of time at peak loading can lead to localized electric service problems
– Voltage dips (dimming lights, damage to expensive electronics)
– Service interruption
– Transformer failure
http://ewh.ieee.org/conf/vppc/Speaker/KS02-4_H_Asgeirsson.pdf" onclick="window.open(this.href);return false;
We have to know what your planning - it looks like 200% load for anything over minutes is a problem and for the time it takes to charge an EV, 100% would be best - including the house loads, 120% sort of ok and 140%+ is getting into problem territory. If you really need that much load continuously - 500 to 600A for 4+ hours, it's going to be some serious distribution transformer and possibly network upgrades... I doubt practically and with some reasonable measures that you'll actually need anything like that unless your charging 3+ Tesla Model S at the same time.