Quote:
Originally Posted by undergroundman
I'm just curious why there were several square miles surrounding "critical facilities", ie hospitals and fire stations, that remained lit up. Why aren't these critical facilities on there own individual switches? Had that been the case, we may had enough spare capacity to do a proper rolling blackout.
More specifically, ERCOT asked Austin to cut back about 50%. Austin Energy said that because they needed the entire remaining 50% to power critical facilities, they were unable to spare capacity for a rolling blackout. If the critical facilities had there own individualized switches, maybe that would've only taken up, say 25%, leaving the other 25% capacity for rolling blackouts. Is this a design flaw in the Austin Energy's local grid (poor disaster planning) or am I way off on my assumptions about how electrical grids work?
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It's not really set up that way. When a circuit is turned off what was being turned off is basically the transformers that step down high voltage electricity to medium voltage electricity. You can usually look over a substation on satellite view and see how many circuits that particular substation is hosting by counting the repeating equipment. Small substations have one or two circuits and larger substations like the Seaholm substation have upwards of 8 circuits. Depending on the mix of business vs residential each circuit represents about 5,000 people. Equipment at this level is very expensive and additional equipment and lines just to serve critical infrastructure would be very expensive. You pay more for delivery of electricity than you do for generation of electricity.
Downstream from the high to medium voltage transformer at the substations that is the start of the circuit you have conduit. The electricity conduit is stepped down once more by the transformers locally. Smaller loads are served by the cans you see hosted on poles. Larger loads are usually green boxes or sometimes on very large facilities the medium voltage is just fed into a transformer vault in the building itself.
So what does this mean? In order to isolate a critical facility to stay on you would have to have the ability to turn off all of the smaller transformers that step down the medium to low voltage that occur on the circuit. Installing such controls on that equipment would be prohibitively expensive. There may be a thousand smaller medium to low voltage transformers that would need connectivity to the internet basically to be able to turn off. The vast majority of these are just passive. When they receive electricity current they step it down in voltage There's nothing fancy about them and that keeps costs down. It's also why utility companies don't just know if you don't have power. There's no magical signal saying something isn't working. Meter data is collected wirelessly nowadays but that's usually someone driving around in a vehicle that is connecting over Wifi.
The solution may be some sort of switch behind the critical load to shave off anything behind that critical load while powering everything in front of it.
Mass remote disconnects of meters is probably being discussed as a solution as well. Those remote disconnect signals still need to get to the meter somehow.
As far as why it didn't seem like anyone was prepared it was because they weren't. No ERCOT scenario went as deep as 50% of load shedding. Highest scenario I've seen in the documentation was 35%. Load shedding events for ERCOT have all been designed for summer peak and it was imagined as an event that would last a couple hours and you'd be unlucky to be cycled off.
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