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NYC explosion: electrical fires are blue?

PostPosted: December 28th, 2018, 1:29 am
by zetreque
The news is reporting that the sky above NYC turned blue from a transformer explosion and electrical fire. ... index.html

So many questions.

What is the physics behind this phenomenon where the "fire" was blue?
Why the blue color? Why is electricity blue?

Was it a massive electrical arc created after the explosion?

Why was the arc going for so long?

How much energy was expelled for this?

Have there been any reportings yet of mutant X-men or The Flash?

I can't wait to find out the details on this.

Electrical Fire Turns NY Night Sky Blue

PostPosted: December 28th, 2018, 2:53 am
by toucana
Transformer fire seen from Brooklyn

Large numbers of New York residents in the Brooklyn and Queens area were startled last night when the sky lit up in an eerie blue glow after a Con Edison electrical transformer exploded during the early hours of the morning.

Social media users posted video images of a ghostly tall column of smoke with a bright aurora of multicolour blue and jade green light that briefly turned the night sky as bright as day. Some wondered if aliens had landed, or a ‘rapture’ had begun.

According to Con Edison engineers, the effect was caused by a brief but intense electrical fire after a couple of transformers tripped offline at the intersection of 20th Avenue and 32nd Street in Astoria which is near a large Con Edison generating plant. The incident did cause power to dip in the La Guardia and Rikers Island neighbourhoods but apparently didn’t cause any lasting outages or grid instability.

Power generating companies like Con Edison use large electrical transformers to either step up or step down the transmission line voltage. AC Electrical power is most efficently transmitted at high voltage, and at relatively low current in order to minimise W = I^2R heating losses in the transmission cables. The most powerful parts of an electrical power distribution grid may run at up to 400 Kilovolts which needs to be progressively scaled down by transformers to deliver 110 VAC domestic line power to households.

Large electrical transformers usually rely on enclosed mineral oil baths to act as coolants, and also as arc suppressants on their heavy duty switching contacts. If an overload occurs because of either a lightning strike, or a catastrophic short-circuit caused by corrosion and insulation failure, then a sizeable explosion can occur. Safety trips can take up to 600 milliseconds to operate which may be too slow to prevent the transformer from self-destructing.

Effectively the damaged transformer behaves like a runaway giant electrical arc welder generating a retina searing blue-white glow, and the mineral oil reservoir in the core of the transformer also catches fire at those temperatures. The large amounts of Copper wire in the transformer windings burns with a bright blue flame. The green colour may come from either Copper sulphates, or more likely from metallic alloys containing Boron that are often used to produce soft magnetic transformer cores that can reduce energy loss in electrical transformers by up to 85%

Re: Electrical Fire Turns NY Night Sky Blue

PostPosted: December 28th, 2018, 6:50 am
by toucana

Re: NYC explosion: electrical fires are blue?

PostPosted: December 28th, 2018, 8:30 am
by toucana
I put a note about this in the main Science News page (Note: now merged with this topic)

I think the blue colour is from the masses of burning Copper wiring in the windings, and the Turquoise green tint seen in some photos probably comes from the soft magnetic Boron alloys used in transformer cores to reduce hysteresis and eddy current losses.

Re: NYC explosion: electrical fires are blue?

PostPosted: December 28th, 2018, 9:02 am
by toucana
This incidentally was a Transmission or step-up transformer that failed. The ConEd high voltage feeders in Manhattan work at up to 345 Kilovolts according to their documentation. The PSCC (prospective short circuit current) or 'crowbar' current that would occur in a dead short L-N or to earth is absolutely enormous - probably millions of amperes, for a brief second or two.

Re: NYC explosion: electrical fires are blue?

PostPosted: December 28th, 2018, 11:45 am
by davidm
Yep, I live in New York City, and was on the Upper East Side last night when I looked up and saw that the whole sky had turned bright blue. It looked exactly like dawn on a clear day. I was stunned, and having lived through 9/11, expecting the worst. What makes it even more eerie is that an hour earlier I had viewed a video called The Day the Dinosaurs Died. It was a computer animation remake of the meteorite strike that killed the dinos, and what unfolded for 24 hours after the rock hit. Just before the rock hit, the whole sky lit up, and then… And I’m looking at that lit-up sky and I’m all like, “Oh, f**k.”

Re: NYC explosion: electrical fires are blue?

PostPosted: December 28th, 2018, 2:31 pm
by zetreque
It appears that electricity is blue mainly because of electrons being excited in the outer shells of nitrogen and oxygen (which make up the earth's atmosphere). The additional flashes of green could come from copper and boron which burn green as toucana pointed out.

It appears to be more complicated though because the mixture of oxygen and nitrogen at different altitudes in the atmosphere and the type of oxygen or nitrogen (diatomic vs monotonic) impact the color as evident in auroras.

I don't suppose we got lucky enough to get some images of this event from the International Space Station...

Re: NYC explosion: electrical fires are blue?

PostPosted: December 28th, 2018, 4:16 pm
by davidm
Off topic, but actually, the video I had finished viewing about an hour before the NYC sky lit up was called Last Day of the Dinosaurs. It’s here.

Not only does the quality of the animation blow me away, but it just boggles the mind that a six-mile-wide chunk of rock could cause a worldwide apocalypse. Yet the vid explains exactly why it did. That this really happened dwarfs any fiction I can think of.

I felt so sorry for the dinosaurs, those beautiful animals! Image I guess the non-existent god was super pissed off that day, more so than usual.

Re: NYC explosion: electrical fires are blue?

PostPosted: December 28th, 2018, 5:39 pm
by zetreque
It must have been all of those sinner dinosaurs.

Right after the NYC explosion I saw some really funny videos on youtube of people posting about aliens and conspiracy theories. I also never heard the word "yo" used so much in such a short period of time in my life.

Re: NYC explosion: electrical fires are blue?

PostPosted: December 29th, 2018, 4:07 am
by toucana
A more detailed explanation by Con Edison says that the Queens failure was not an inductive transformer explosion as first reported, but a massive electrical arc fire in a related voltage monitoring and control system known as a CCPD (coupling capacitor potential device). arc flash in which electricity delivered via a 138,000-volt transmission line jumped from one point to another, ionizing the very air through which it leapt. The energy was too great to be constrained to a straight trajectory, and it began to arc with its own power. The arc grew higher and higher, as did the heat it generated.

“Temperatures can reach as high as 35,000 degrees Fahrenheit,” notes a General Electric fact sheet. “This is hotter than the surface of the sun.”

The remarkable Tiffany blue or turquoise green colour came from the combustion of vaporized aluminum metal. In normal circumstances, aluminum metal burns with a white or silvery light, but at the extraordinarily high temperatures found in this type of electrical arc fire, the flame colour tips towards this shade of blue which spread through and was reflected by the low-lying cloud cover.