Initial Power Draw After Power Outage

[DerbyDad03]

We had a power outage last night. It was in the mid-80's and I'm sure that most of us had our AC units just sitting there waiting to spin up as soon as the power came back on - I know I did.

So how is that initial power requirement handled by the power company?

Even in a relatively small outage like we had, the initial demand as everybody's AC units, cable boxes, lights, pool filters, fans, fridges & freezers, etc. all come on at the exact same moment must be huge.

How does the power company soften the impact on their equipment?

[dpb]

Generally first by staging the return of any larger sections then that's what "spinning reserve" is for for the makeup.

There will be some voltage sag and short term redistribution within the local grid as well.

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[bob haller]

plus most ACs have a high current limit switch that opens for a moment when overloaded like trying to start after a outage

[cottone40511]

Most AC and refrigeration equipment have a delay that usefully takes up to 5 min or more after power is interrupted, allowing the pressure in the compressor to equalize. If the pressure is not equalized it is likely that the compressor will try and start, but instead draw a large current and trip whatever high current device there is in the system. It is not desirable not to use the high current limiting device as it can shorting the life of the compressor.

[jamesgangnc]

I believe he is refering to a longer delay without power. In which case the compressor will try to start immediately.

[bud--]

Sounds good for a really large area.

Most power restores are probably not much power relative to the capacity of the grid.

Motors and incandescents briefly draw about 6x normal current when they are turned on.

[hrhofmann]

I usually notice a fair amount of flickering when our local elect co restores power, as other sections are added onlne I suppose.