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-   -   Lightning Storm --Strike at 3 phase HV Pole (http://www.diychatroom.com/f18/lightning-storm-strike-3-phase-hv-pole-107383/)

Perry401 06-11-2011 06:44 PM

Lightning Storm --Strike at 3 phase HV Pole
 
Last evening, there was a lightning storm, and I witnessed a strike on a nearby 3-phase high-voltage line. First was nearby "crackling" noise from the air. Then a lightning bolt found it's way to one of the conductors on a 3-phase power line about a half-block away. Then there was the "snap" and thunder -- almost instantanious with the lightning strike. Then the lightning bolt maintained itself for several seconds. During this time, an arc established across what appeared to be some type of High Voltage Disconnect switch. As the lightning bolt finally resided, there was a puff of smoke -- not unlike what some fireworks put out. But even without the lightning, the arc was maintained and glowed brightly -- like a stage arc lamp. There were some sort of sensors or indicators mounted one on each line of the 3-phase power. These blinked on and off red for some time. After a minute, the arc was still established, and glowing as bright as ever. After about 2 minutes, the sensors stopped blinking and power to the neighborhood was dropped. I called the power company and they said they shut down the 3-phase line remotely. Had they not done this, the arc would have continued indefinately. A Wendy's restaurant, as well as several other businesses were still closed 24 hours later due to damage from the strike. The top of the pole near the arc point was almost burnt in half, and crews were out to fix it within an hour or so.

As impressive as the lightning had been, what was scary was the fact that an arc was established by the lightning and then maintained by the power company power. Apparently, whatever fusing the power company may have used on the primary power wiring either failed to work, or the arc did not draw enough current to trip it in a timely manner. I have not seen the damage at the Wendy's, but they said on the news that it will take "several days" for the damage from the storm to be repaired (the restaurant has it's own ground-mounted transformers).

The whole spectacle makes me appreciate the power of lightning and makes me worry a bit about what would happen if a similar lightning strike were to happen on the drop to a residence.

Leah Frances 06-11-2011 07:05 PM

Cool.

joed 06-11-2011 08:26 PM

Likely some sort of line switch opened but the current through the line was enough to maintain an arc until the power was shut down.
When you have thousands of amps flowing through a circuit at high voltage it maintain a very long arc the same as an arc welder.

AllanJ 06-12-2011 08:50 AM

Most of the damage was caused by the lightning bolt itself. The lightning can find its way into homes as well (through service entracnce cables), jumping the insulation between closely spaced conductors such as in Romex cables and likely burning out many feet of cable inside walls.

A medium tension line (primary line) on a street power pole can fall on the 120/240 volt (secondary lines) and similarly fry the wiring in homes. It can require a complete rewiring of the house as there is no way to find out exactly wat got fried.

frenchelectrican 06-13-2011 03:45 AM

Most home I ran into where they have lighting strike either directally or indirectally can do pretty good damage to your electrical system.

The amount to replace the wiring will varies a bit but we will do few diffrent ways to inspect the exsting wiring system.

If more than just a couple circuit typically will end up rewired the whole place { check with your insurance company to see how far they will cover the wiring replacement due some are little tricky with it }

And I used the Megger tester to see how far the damage to the exsting circuits and sometime Megger may not catch it but useally they do catch it even if you look from outside { exteral } view but inside may be allready cooked or flashed over and do the interal damage which you may not see it.

There will be other peoples will chime in with more details if they know about it as well.

Merci,
Marc


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