Re: Z-Machine Sparkage - Substation Fault

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

Original poster: "Terry Fritz" <teslalist-at-qwest-dot-net>

Hi,

Having worked on many a substation, here's my guess as to what is going on.

The load hum is probably a low side power arc to ground.  The arc is 
probably several feet long and burning the crap out of what ever it "was" 
that started it all.  Given the location, this station looks like it 
basically converts ~200kV AC down to 33,000 or 14,400 for local 
distribution.  The power "in" is probably 200kV at say 500 amps three phase 
for a toasty perhaps 170 Megawatts of power.  Since the arc is sustained, 
the power is not enough to trip the downstream equipment.  So maybe it's 
only 100 MW ;-))  The arc seems to be on the low voltage side since there 
is obviously very high currents beyond 500 amps.

The stations breakers and control equipment are supposed to trip it all out 
safely, but it ain't a working here ;-))  Very possibly a breaker is what 
failed so there is no local control.  If the 200+ kV go into the control 
side of the station, all bets are off in trying to just "turn it off" since 
the control equipment is probably fried.  It is surprising the line carrier 
and other fail-safe equipment does not instantly signal the down stream 
station(s), but it sort of depends on what went wrong and how it was all 
set up.  But at this point, the ship is not responding to the wheel ;-))

The people back in the control rooms just see all kinds of high currents 
and loss of communications to a substation.  They are trying to figure it 
out how to take it down manually through other stations but they have no 
idea what exactly is going on so they are just seeing charts and numbers 
flipping by...  They know something "bad" is going on, but not quite sure 
what.  They "can" monitor police and fire but they usually have the volume 
way down...  They used to have rows of pin printers that would suddenly 
start to print "events" like mad...  But good luck in trying to figure out 
something like this "fast"...

Eventually, the high power must have blown something inside the transformer 
to cause massive overpressure and blowing it's seams.  The oil sprays 
out.  You can see a loud explosion high in the high voltage side which 
probably did finally trip the downstream stations as that big 200kV got 
dead shorted (those currents are "high" ;-))  The spraying oil ignites and 
the fire ball and all...  This is why non-flammable PCB oil was so popular ;-))

Nasty fire.  Probably just have to let it all burn out since it is very 
hard to be sure all the power is removed before the fire folks go pouring 
water on things.  Not like there is anything left to save...

This is a wonderful video of what most people only see after things are all 
burnt up.  It is a good example of what "real power" is flowing through the 
electrical grids!!  I wonder if a golf ball hit an oil filled 
insulator...  Probably never knew what exactly happened...

BTW - We all used oil breakers for everything.  Never had any explosive 
fuses.  They had explosives around in case they had to clear "blow-up" 
equipment ;-))  But at the power transmission level, there were no "fuses".

Cheers,

         Terry


At 01:59 PM 4/13/2003 -0500, you wrote:
>Hi Godfrey,
>
>Jim and Dave have already provided some excellent information on the 
>internal structure and operation of expulsion fuses.
>
>The loud humming sound is most likely coming from 120 Hz vibrations of the 
>windings as tremendous repulsion forces act between the primary and 
>secondary under fault conditions (Lenz's Law). To combat these forces, 
>power transformer manufacturers use special interleaved winding techniques 
>that partially cancel the forces (at least for inner winding sections). A 
>sustained low impedance short between 2 or more phases (called a "bolted 
>fault") can easily bend heavy bus bars and windings like pretzels. Under 
>fault conditions a low impedance power transformer driven from a low 
>impedance source can create forces which can literally tear it apart. 
>Inductive reactance is purposely added to help protect the transformer and 
>upstream equipment from this case.
>
>BTW, the cooking transformer in this substation actually held together 
>pretty well... at least for a while.  :^)
>
>Best regards,
>
>-- Bert --
>--
>--------------------------------------------------
>Out-of-Print Physics and Engineering Books and
>coins shrunk by ultrastrong electromagnetic fields!
>Stoneridge Engineering: http://www.teslamania-dot-com
>--------------------------------------------------
>
>Tesla list wrote:
>>Original poster: "Godfrey Loudner by way of Terry Fritz 
>><teslalist-at-qwest-dot-net>" <ggreen-at-gwtc-dot-net>
>>
>>Do these expulsion fuses have high explosive charges inside to blow out
>>arcs? Was that loud humming sound made by bussing transformer laminations?
>>Godfrey Loudner
>>  >I'm going to show at an electrical
>>  > safety training class at work, just to illustrate how bad a >high power
>>fault
>>
>>.
>
>
>
>