Connections to dirt do little below 600 volts

[mgookin]

I think what kwired said earlier in the thread about there not being a low enough resistance in the path back to the source was likely accurate- even with the downed line touching/very near all of that metal that was in good contact with the soil, just too much impedance.

And even though it has been pointed out about the voltage difference in video versus topic posting and iwire has said it was a mistake , I think it's still a good thread and still gives food for thought for the "earth" crowd- if soil as a fault clearing often doesn't work for higher voltages ( it for sure didn't work for the high voltage in the video), why would they believe it would be effective for the simple lower voltages used everywhere else?

You got me laughing on that one. Spot on.
Next time some guy says the earth is going to clear a fault on his 1/4 hp drill, show him that video.

 

[meternerd]

High voltage fuse did not operate? Protective relaying did not work? :?

This type of fault is kinda typical in areas where dry, rocky soil exists. "High voltage" (which is really medium voltage for most distribution) line protection for ground faults always depends of fault current levels, which always depends on impedance back to the fault clearing device, whether a cutout, recloser, or relay controlled breaker. We add pole grounds that help increase fault current, but it still depends on the dirt to get back to the pole...not always enough to clear a fault. Just my humble opinion, though. If yours is different, I'll patiently explain why you're wrong.:happyyes:

 

[__dan]

Saw one lightning damage, had to look at it several times because it was unbelievable the path it took. Came down a tree, jumped three feet or so to a fence, traveled ~ 90 feet down the fence to the house, but it had to jump another three feet to the house and then three feet of house, blowing off the siding along the way, to the meter socket where it entered the house. They replaced some plug in stuff and the phones but I found it had blown the foils off the burner control PCB.

Obviously the energy was being dissipated at every point along the path before reaching the house but enough remained to cause minor damage.

Seen a direct strike blow a 30" oak completely in half 20 feet up and cover the yard with toothpicks in a 20 ft radius.

No one says the earth path has to fault clear and trip the OCPD, unless you have suitable GFCI.

Safetywise, you can have intentional and unintentional connections to earth. If you don't require the intentional connection, you will only have the unintentional, things touching and in contact but not bolted together with a rated carrying capacity. Things just touching will have localized resistance at the casual contacts and burning.

You can see the effect of the unintentional paths in the video. The swingset carries well except at the joints which are smoking. That's where the resistance and localized heat is. At some point the swingset's carrying capacity is exceeded (resistance drops and current flow increases) and the path flashes over through the air surrounding the swingset, plasma having a lower impedance than the air.