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Re: 250,000 volt nuclear transformer
Hello all,
I wanted to echo those who have replied to the radiation issue of the the
XFMR from
the nuclear plant. I am a Reactor Operator at a Nuclear power plant in
Ohio. These
types of capacitively coupled potential devices are used in the plant's
switchyard.
They would never have been inside the radiologically restricted area and
should not
have any contamination concerns. I consulted with a system engineer
responsible for
our 345kV switchyard as to these devices operation in Tesla coil use. I've
included
his response. Hope this helps.
Randy Burk
In a nutshell a ccpd is an overgrown instrument transformer.
It usually has two or three low wattage windings to drive meters or
protective relays, say 400VA at 120VAC that is 3.33A at power factor 1.
The huge size is to compensate for the withstand voltage on the high
side.
Example: for a three phase system at 345,000VAC phase to phase the line
to ground voltage is about 200,000VAC (345000/1.73). The ccpd is a 60hz
voltage divider. Usually 200,000VAC is dropped across the 60 hz
impedance of a string of capacitors and at the 25,000VAC point in the
string they parallel a transformer, an inductor with a 60 hz impedance.
The output of the transformer is designed to provide a ratio to the
voltage being sensed. The whole thing can be thought of as a big tuned
filter circuit designed for 60 hz.
So let's say you just backfed this baby with 60 hz, 120VAC and 3.33A if
you measured the output of the top terminal to ground, with proper
safety practices! you would see 60 hz, 200,000VAC with 0.002A.
This baby is very dangerous, with lethal voltages.
If this was at a sale it most likely has a fried transformer or failing
capacitors. It may be good for parts but the capacitors probably would
have low duty cycles and they have a tendency to explode if overheated.
They usually are a porcelain housing containing a stack of metal film
capacitors immersed in oil. If the transformer is an oil filled type it
may be in good shape but again it is a low power device. If the
transformer is solid insulation it most likely is cracked or burnt out.
Treat all high voltage parts with respect. They can fail and hurt you
bad. While handling the capacitors keep them shorted out. Ground out
the high voltage winding of the transformer when working on it too.
I do not know what the high frequency characteristics of this equipment
is like, just watch out for overheating. These piece parts are normal
passive electrical devices and can be tested to determine their values,
again follow all high voltage safety practices.
Tesla List wrote:
> Original Poster: "David Trimmell" <davidt-at-pond-dot-net>
>
> Hi Andy,
>
> I can verify that switch yard equipment is outside the RCA (radiologically
> controlled area) of the Nuclear Power plant. Not much chance for
> contamination. This I know from working at many Power plants myself as a
> Health Physics Tech. Allways thought the output from a 1000 Megawatt
> generator (gernerally 22KV, 3F) would mak fore a nice PSU ;->
>
> Regards,
>
> David Trimmell
>
> On Wed, 22 Mar 2000, Tesla List wrote:
>
> > Original Poster: "Andy Cleary" <gemware2-at-dreamscape-dot-com>
> >
> > I have received numerous questions about the radiation - and
truthfully, I
> > don't know. I assume that it was no place near the reactor core, and the
> > only reason why it was removed is because it was "obsolete".
> > I haven't been able to get it home yet, it supposedly weighs 1000
lbs.
> > Actually, it has caused quite a disturbance in the family. My friend's
> > mother has contacted my mother, and they are both worried about it. As
soon
> > as I can get it home I will post more info about it. All that I can do now
> > is recall from my (usually not so good) memory.
> > From what I can remember, the thing's base is only about 2ft x
2ft, but it
> > is about 6 feet tall. I would say that 4ft of the height is what looked to
> > be a giant insulator. On the top is, I would say, a 2" bolt, maybe for HV
> > connection. Just before I bid on it I found a hatch, and looked in. All
> > that I could see (it was dark) was a 10,000 volt capacitor, and some other
> > stuff inside. I have to wait to get it home before I can get more info. I
> > didn't know how much trouble that $10 thing was going to be!
> > Thank you for all of the info, everybody. I will continue posting
progress.
> >
> > -Andy C.
> >
> > -----Original Message-----
> > From: Tesla List [mailto:tesla-at-pupman-dot-com]
> > Sent: Monday, March 20, 2000 10:16 PM
> > To: tesla-at-pupman-dot-com
> > Subject: Re: 250,000 volt nuclear transformer
> >
> >
> > Original Poster: Rscopper-at-aol-dot-com
> >
> > Personally, I don't think I would ever purchase anything "formerly used
in a
> > nuclear power plant" Did you check it for radiation?
> >
> > It would be interesting to know how they insulated the components inside to
> > that voltage - are you sure it hooked directly to the 250K line? Did you
> > get
> > any of the 6-foot insulators also?
> >
> > If you take it apart, post some pictures of the inside. I don't think
> > you'll
> > get 250K out, since you'll have to current limit the heck out of it to run
> > it
> > off your house wiring. To get the maximum KW out, you have to put the same
> > KW in.
> >
> > Scott
> >
> > << Original Poster: "Andy Cleary" <gemware2-at-dreamscape-dot-com>
> >
> > I recently bought a transformer that steps down 250,000 volts to 115
> > volts,
> > formerly used in a nuclear power plant. It weighs about 1000 lbs. and
is at
> > least 5 feet tall. I think it said that it was a capacitively coupled
> > potential transformer. I was wondering if you could hook it up in reverse
> > and get 250,000 volts? Are pole pigs connected in reverse for high
> > voltage?
> > Unfortunately I don't have it now, because I couldn't get it home to test.
> > If anyone knows if it will work or have any other comments then please
> > respond. Thanks,
> >
> > -Andy
> >
> > >>
> >
> >
> >
> >