Re: New 8 second long 550 kV Power Arc

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: Bert Hickman <bert.hickman-at-aquila-dot-net> 

Hi Chris,

Normally air break switches are opened and closed with the circuit 
de-energized or opened only while carrying low reactive currents. They are 
used to reconfigure HV sections or to connect/disconnect reactive elements. 
Heavy duty circuit interruption is done by huge Oil Circuit Breaker (OCB) 
or air blast circuit breakers. These breakers are designed to break a load 
or fault current by intentionally creating a controlled arc inside the 
breaker. The hot arc channel is then rapidly stretched and cooled to 
extinguish it in at an AC current zero crossing. The power arc must not be 
quenched too quickly since inductive elements may generate large switching 
transients that can damage equipment, cause insulation flashovers, or cause 
the extinguished arc to restrike.

I've received some additional information about this MPEG from some power 
folks at Sargent and Lundy. This was actually part of a diagnostic test to 
help resolve problems that a California utility was having when switching 
HV line reactors in and out of the transmission circuit (as part of 
voltage/load management). These huge reactors can be seen to the right of 
the switches at the end of the MPEG. During the test, the 500 kV lines were 
cleared at both ends, and a 500 kV OCB was isolated so it would energize 
just the line reactors from the operating bus. The line reactors were 
energized when the circuit switcher was opened. Apparently, one of the air 
break switchers (Phase C) had a problem, causing an incredible arc.

BTW, this arc did NOT extinguish by itself. Instead, the upstream 500 kV 
OCB was commanded to open up the circuit, finally killing the arc. That's 
why it seems to stop so abruptly. Fortunately, the utility had set up a 
cameras to capture abnormal behavior... and that's exactly what they 
caught!  :^)

Best regards,

-- Bert --

Tesla list wrote:

>Original poster: Chris Roberts <quezacotl_14000000000000-at-yahoo-dot-com>
>So what purpose do those air break switches serve? Do they usually open 
>hot? What would cause that one switch to arc while normally it dosen't? 
>(At least I would imagine this is a fairly rare occurence) Just trying to 
>understand why this would happen, other than just a couple of bored 
>utility workers wanting to see something really cool. =D
>By the way - AWESOME movie!
>Tesla list <tesla-at-pupman-dot-com> wrote:
>Original poster: Bert Hickman
>For all fans of Arcs and Sparks,
>A friend of mine at Fermilab just sent me a 1.5 MB MPEG of a 500 kV air
>break switch opening hot. One of the three phases has a problem
>disconnecting, resulting in one awesome power arc that's gotta' be at least
>50 feet long. It lends a new meaning to the term power arcing.
>And those utility guys have all the fun... listen to the guy whooping it up
>at the end of the MPEG. :^)
>See it at: http://205.243.100.155/frames/longarc.htm
>Merry Christmas,
>-- Bert --