Why does power flicker in a storm instead of going and staying out?

August 30, 2023 1:31 PM

So we're getting the first bits of hurricane Idalia and power has flickered. Which makes me wonder what's going to make it flicker, instead of just going out and staying out.

Flickering is obviously better than going and staying out, but I am curious about the infrastructure that allows/causes flickering. Does anyone know the details of what's happening in these situations? Are there multiple systems in place so that if so one line goes down, then there are several possible paths for power to follow? School me please!

Personal note: things are fine, am essentially in a bunker with plenty of resources to weather several weeks, so no worries!

posted by Brandon Blatcher to Science & Nature (7 answers total)

Non-expert weighing in - It is a (generally) redundant network of power lines. Power distribution is a balancing act of dynamically matching generated supply with demand. The flickering is indicative of an imbalance.
posted by Jessica Savitch's Coke Spoon at 2:15 PM on August 30, 2023

Best answer: oes anyone know the details of what's happening in these situations? Are there multiple systems in place so that if so one line goes down, then there are several possible paths for power to follow? School me please!


That's one reason. Another is that equipment is checking for arcing conditions, and wind and rain can create those, or more serious things like tree branches or lighting strikes. One of these pieces of equipment is an OCR - oil circuit recloser.
posted by The_Vegetables at 2:17 PM on August 30, 2023

That link also inadvertently describes how forrest fires start: "“However, a tree branch across a power line may cause the OCR to open and reclose up to three times, causing three blinks as the OCR attempts to burn off or clear the branch causing the fault"
posted by The_Vegetables at 2:20 PM on August 30, 2023 [1 favorite]

I grew up in Savannah and my parents used to suggest this was from spanish moss getting blown into the power lines from all the low hanging trees. This is obviously not exclusively the reason, but it was easy to imagine.
posted by phunniemee at 2:48 PM on August 30, 2023

Best answer: The other side of a voltage spike is the brownout, or voltage drop. Both spikes and brownouts can be caused by storms or intentionally by power line operators. When I lived someplace that regularly had power issues we would go around and unplug or trip the breaker for many of the expensive/fragile appliances in the house.

The electrical grid is sorta a grid of regional systems. The system where you live will have a bunch of substations that are interconnected to power sources, other substations and your house. This interactive site that lets you control a regional power system lets you route power around.
posted by zenon at 3:40 PM on August 30, 2023 [1 favorite]

Where I am the lights flicker mainly during wind/lightning storms, and when they don’t go out altogether and I’ve gone to the power outage page maintained by local utilities, I’ll always see a fairly nearby power outage.

So I think an outage will tend to drag down the whole local grid until circuit breakers kick in and isolate it to a relatively small area.
posted by jamjam at 3:41 PM on August 30, 2023 [2 favorites]

Best answer: Momentary flickers (the kind that some electronics will continue operating through) are caused by momentary arcing (either between phases on the three phase distribution second your area or to a poorly located tree) dragging down the voltage, but not long enough to blow a fuse, or lightning arrestors conducting to earth for a couple of AC cycles when they reach their breakdown voltage.

You can tell the difference from a recloser tripping because a recloser is a mechanical device that takes a noticable time to close back in after detecting an overcurrent condition. The lights will go out for half a second to a couple of seconds before blinking back on.
posted by wierdo at 4:51 PM on August 30, 2023 [6 favorites]