Wife and I just noticed a flash of lightning outside and a couple seconds later heard thunder and our lights flickered like we were going to lose power. What is happening here?
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Basically there is a voltage drop. Voltage drops if there is a short in the system (or when more power is used than produced, but that isn’t the case here). A short is when the high voltage line gets connected to the neutral line (or ground) without proper resistance. Imagine you stick a paper clip in a plug so you connect both sides. Sparks, and current. Your house has a breaker that will trip if you do that, but for a breif second the voltage will drop and high current will flow through the wires.
In the case of a storm, kind of the same thing happens, at a bigger scale.. like some wires crossed and there was a short causing the voltage to drop. Could be a branch pushing wires together, or a pole falling and ripping wires down. Like the breakers in your house, the power company has breakers that will prevent the short taking out the whole grid. But for a second the short effected your power by reducing the voltage to the point your lights didn’t work.
Could be a branch touching a power line. If it were directly from the lightning, I wouldn’t expect there to be any delay in the effect on your house. It would be lightning, lights go out, thunder, all probably really close together.
The approaching storm causes damage to the electrical network. This can be because lightning struck somewhere and damaged some of the equipment, because a tree fell over into power lines, or because the power lines themselves were downed by wind or flooding or the like. In any case, something disrupted the flow of power somewhere in the electrical network.
Fortunately, those networks are *redundant*: they have multiple paths for power to get from A to B throughout most of their area. When one part of the network fails, electrical switches in other parts of the network flip over to direct power through other parts of it. This doesn’t happen instantly, though, so there’s a brief delay before the rerouted power is available. This is visible to you as a brownout (drop in voltage, so called because of the dimming of incandescent light bulbs) or brief blackout (power failure) while the rerouting completes.
Utility Switchgear expert here. Many comments here are potential reasons. One common reason is tree branches or debris cause a short between the power lines. There are devices called Reclosers which are specifically designed to turn power off once that short is recognized, and then return power back on, aka ‘reclose’, as little as 0.15 seconds later. This is so quick, you may not even notice lights dim. The short circuit is often temporary in these cases where tree branches fall off or the debris clears so power can be restored in less than a second. If the debris is still present after the first ‘reclose’ the device may try again two or three more times before turning power off until crews can fix the problem.
Could be that lightning struck a distribution line. There are lightning protection systems that activate when the line voltage goes way too high, as will happen during a lightning strike. When this happens, all the energy on the line is dumped to earth, interrupting the flow of power. As soon as the strike is over and the voltage falls below a certain point the lightning protection equipment stops conducting electricity and power begins to flow again.
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