Here is an amazing video of a power line that fell on a tree. It’s live and is burning the tree for a minute and emitting a loud whine then just after the minute mark there’s an impressive ZAP, ZAP, ZAP, BOOM, BOOM, BOOM as something gives and it explodes. It’s pretty wild, I’ve only heard zap sounds like that in movies. If I had to explain it, I’d say “The darn thing shorted out”, but I’m wondering about the real science behind it.
What caused the loud whine in the first minute of the video?
What caused the three loud (and bright) zap sounds?
What caused the two or three explosions further down the line?
I’ve shorted out wires and made a spark and a “pop,” is the whine like that except a million pops per second making it sound like a continuous whine? I’m guessing that the wire melted and the zap sound is from electricity jumping from one side of the wire to the other but, even if that’s right (a big if), I can’t explain why it causes the zap sound.
So, can anyone walk us through what is happening in the video?
**What caused the loud whine in the first minute of the video?
**Just a guess that it is steam escaping from the green tree as it heats up. If you’ve ever burned green branches in a campfire you’ll know what I mean.
**What caused the three loud (and bright) zap sounds?
**Dunno.
**What caused the two or three explosions further down the line?
**I think the power line finally breaks or melts and hits that chain link fence.
What caused the three loud (and bright) zap sounds?
I would guess would be steam pressure building up and bursting through the wood, much like green fire wood poping. The zaps were probaly the wires bing blown apart and falling back close together.
What caused the two or three explosions further down the line?
The final explosion probably spit apart one or both lines, One or more then fell the rest of the way to the ground and shorted out.
Flash steaming of water seems to cause most of the sounds.
I was thinking that a transformer’s breaker going would cause a loud boom and was anticipating that as I watched. But these were very weak booms compared to what I’ve heard. (And I heard the one outside our house go boom just a couple weeks ago. Big boom, shake and reverberation.)
The three loud/bright zaps appear to be short-circuit events. When the tree is getting cooked, it’s a high-resistance circuit element that limits the amount of current flowing through the wires. At some point, something created a low-resistance connection to ground, and the wire started flowing a LOT of current; it just happened three times in a row. The pitch is 120 Hertz, consistent with AC current operating at 60 Hertz.
The sound you hear (not in this video) isn’t a conventional mechanical circuit breaker - it’s an expulsion fuse. This is a fuse designed so that when the fusible link melts, it ignites boric acid around it, producing gases that rapidly blast the molten link away, quickly eliminating any material that might allow an arc to continue conducting electricity through the vaporized link. It’s loud, scares the hell out of you, and works really well to rapidly and reliably interrupt high-voltage circuits.
Besides the noise caused by flash steaming of the water and other fluids in the tree, the tree could end up exploding as a result. The large booms sound too loud for that, but I don’t really have a frame of reference to determine that. However, the exploding wood could have broken the line, or contributed to the electrical related explosion described above. People often see trees that have been split by lightning, assuming the lightning itself physically seperated the tree, but it is the heat generated that causes the tree to explode and split.
(Regarding my previous post about hearing my local transformer popping.)
Interesting. But a followup question:
Most of the time the utility worker just pushes a big switch back into position using a very long pole. This time, he went up in the cherry picker and worked on it a bit. Noticed him cleaning off stuff from the switch.
If it’s a destructive process, why would just flipping it back set things right again?
(Yeah, about once every 2 years it blows. This last one was in clear daylight. Maybe an animal decided to go for a Darwin Award. We have an EMC. Good: cheap rates on electricity and gas. Bad: Not as reliable as The Big Company.)
You sure that’s all he’s doing? I’ll wager that he opened that mechanical circuit breaker (or another one elsewhere), replaced the expulsion fuse, and then closed the breaker again.
Attempting to open a HV circuit with an ordinary air-gap breaker doesn’t create a “BOOM,” it creates an arc, like this terrifying monster. In that video, a HV breaker (opening elsewhere finally interrupts the circuit and kills the monster.
There’s one of those at the corner across the street from me and I have watched the man replace a blown fuse many times. He doesn’t just push it back up into place, first he removes the holder? that swings down and puts a new fuse in it, then reattaches the holder and finally pushes the fuse back up into place, and my electricity comes back on. Yay.
Missed the edit window. I don’t think he actually removes the holder that swings down when the fuse blows, he just removes the fuse and puts in a new one before pushing it back up to the contacts.