The second link says:

"each utility is required to lower the demand on its system based on its percentage of the historic ERCOT peak demand.

"each utility is responsible for determining how to implement the required demand reduction, most utilities use rotating outages for this purpose."

There's about 25 different utilities, so who knows what each does.

I'm surprised voltage reduction isn't used. It's very effective at reducing resistive loads (ie: heaters and incandescent lights).

The grid has basically zero capability to change the voltage; frequency is all that matters. Frequency is so low that in the past hour any power line time base has fallen over 5.5 seconds behind. That’s a massive drop in frequency.

No, voltage can be dropped a bit. "Brownouts" are a thing. But they're less effective than they used to be, because everything with a switching power supply will draw more current if the input voltage drops. That's now a big fraction of the load.

Surely it’s not a big fraction of the load tonight. This whole problem is being caused by heaters.

But heaters on thermostats will just run more if they are putting out less wattage. So across your whole population of houses, you won't move that part of demand much (maybe a few were already running at 100% duty cycle).

It's a tool where I am. The grid operator does tests for 3% and 5% reductions:

https://www.ieso.ca/Corporate-IESO/Media/News-Releases/2019/...

Would be very effective with the space-heater (or oven?) driven demand right now in Texas. Not effective for A/C-driven demand (motors will draw more current).

>Frequency is so low that in the past hour any power line time base has fallen over 5.5 seconds behind. That’s a massive drop in frequency.

Out of curiosity, where did you find this?