You've probably heard of Thursday's incident at the Edison station in New York, which temporarily dropped its power at La Guardia and set the night sky glowing with a strange aquamarine. We wondered: What made it so blue?
Con Ed initially chirped a Very restrained A comment to describe the huge explosion seen by thousands, if not hundreds of thousands of people: "There was a short electric fire at our substation in Astoria which involved several electrical transformers and caused the immersion in the region."
But this morning Con said it was true No Fire, and it was a transformer explosion, according to WABC-TV: "The electrical fault on 138,000 volt equipment caused a sustained arc flash that was visible on a wide surface.The equipment that was damaged was isolated to one part inside the station."
Arctic flashes occur when an electrical current passes through a medium that does not normally lead, like air, between two electrodes. This ionizes the medium and creates an "electric arc" between the electrodes, characterized by high current, high temperature, and visible flash – a result of ionization in the medium. This concept employed arc welding, and even lamps during the late 19th century. Despite other reports, it is not the same lightning, which is a spark or a discharge. Arches are usually sustained over a long period of time.
The blue color was the result of excited air molecules. If you remember back to middle school, different excited gases release different colors. Previous transformer explosions have also brought a bluish glow.
"It's Corona," said Peter Sauer, a professor of electrical and computer engineering at the University of Illinois, Lagos. "It happens every time there is an arc, there is a blue light from the corona discharge on high-voltage transmission lines, especially when it's humid, it's ionizing air."
Basically, it's short on a relatively high voltage line, he said. It could have been caused by failing insulation, debris, or something else; We will not know for sure until Con Ed investigates.
Ark flashes are particularly bright and hot, and companies are employing different methods to stop these arches forming between the electrodes. No doubt, one of these methods failed yesterday. And so, though scary, the blue flash was not aliens and was not even strange, necessarily. It was just some damaged electrical equipment and lots of ionized air.