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Was going to try to lay out in non-technical language why our power went out early Monday & stayed off for those trying to decipher tweets/news, but w/o internet, I haven't been able to. Now that I'm online for a few hrs, here it is in case it's still helpful. (1/20)
The electric “grid” is an interconnected network that moves electricity from those producing power (generators) to those consuming the power (users like me and you and businesses). How much we consume, our demand for electricity, is referred to as “load.” (2/20)
Often the most desirable location for generation stations (near fuel or water source) is not close to load centers (concentration of electricity consumers, such as cities). So power must sometimes travel long distances over a network of circuits called transmission lines, &(3/20)
ultimately through smaller circuits called distribution lines to your house. For electricity to flow through this interconnected network (because of highly technical reasons that I do not pretend to understand including b/c elec. cannot easily be stored in large amounts), (4/20)
the supply (the electricity being produced) flowing through the network at any point in time must more or less match the demand (electricity that consumers are using) at that same point in time. (5/20)
ERCOT (the entity) is the “Independent System Operator” or “ISO” that manages the flow of electricity on the transmission system to maintain this equilibrium for about 90% of the load in Texas. (Different ISOs manage the rest.) (6/20)
ERCOT does not own the generation stations or transmission lines; it compares its role to that of an air traffic controller. (7/20)
If the supply/demand equilibrium is not maintained, “cascading failures” can occur. Eg, if a large generator goes down on one part of the grid, unless compensated for quickly by firing up another generator (if available) or reducing the load served by that generator... (8/20)
load shifts to nearby transmission lines, which are pushed beyond their limits (capacity) so they become overloaded and shift their load onto other lines which become overloaded, and so on and so forth. (9/20)
Cascading failures is approaching worst-case scenario for an electric grid! Cascading failures can lead to system collapse and complete power blackout. A power blackout can last weeks as all damaged elements of the system are repaired/replaced. (10/20)
Now to our specific situation. ERCOT reported that approximately 34,000 MW of normally available electricity (generation) was forced off the system during this event. (There will undoubtedly be investigations into why this happened after the crisis.) (11/20)
Picking a point in time, the 2/17/20 9:09am update from ERCOT had generation capacity (or supply) at 46,586 MW—as opposed to the ~80,000 MW we would have had in theory to meet demand without these failures at the generation level. (12/20)
The ~47,000 MW we did have at that time wasn't nearly enough to meet the spike in demand due to extremely cold temps over long duration. More on why that is here: https://www.forbes.com/sites/joshuarhodes/2021/02/14/valentines-day-giving-the-texas-electric-grid-the-cold-shoulder/ (13/20)
To avoid cascading failures, ERCOT directed service providers to “shed load.” Shedding load essentially= manually reducing demand by turning off power to certain users. Remember: ERCOT needs load to match the available supply, which was significantly reduced due to outages(14/20)
On 2/15, ERCOT needed to reduce total load by 16,500 MW. Each service provider (in our case, Austin Energy) is responsible for contributing to this reduction. The amount each service provider must contribute is based on that service provider’s % of total ERCOT load. (15/20)
My understanding is that this % translated to so many MWs that Austin Energy had to shut down almost all non-critical circuits. (Critical circuits have hospitals, control centers, 911, water/wastewater plants, etc. on them so are prioritized in this situation.) (16/20)
If you, like me, experienced a sustained outage, it is likely b/c you are not on a critical circuit. The outages in Austin were not “rolling” because the non-critical circuits alone roughly equaled the amount of demand (load) that AE needed to manually eliminate (shed). (17/20)
There were no other non-critical circuits available to put into outage rotation. As generation begins to come back online, AE will be able to restore circuits (and, in theory, begin to rotate outages). (18/20)
Just a quick look at the ERCOT app had generation capacity at 64,244 MW at 1:49pm on 2/18 (significantly up from ~47,000 yesterday morning). So things are moving in the right direction. (19/20)
This is not a comment on market design or root causes, etc. Merely trying to help people understand some of the terminology being used in communications/reports. (/end)
