Distibution Transformer Explosions

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On big substation transformers proper protection is in place in the form of a Buchholtz relay.
Usually arcing causes ehtylene gas and carbon CO, and CO2

This one collects gas and if a certain amount has filled up a chamber in between the main tank and header tank, it triggers an alarm, if not actioned it trips the supply to the TX.

If a serious arc causes a lot of gas and expansion the Buchholtz relay will trip the supply immidiately.

Additional alarms are for overcurrent, oil temperature, winding temperature and restrictive earth faults.
 
Hi, no those don't !

I talk here about the 10 and 20 MVA substation TX's.
These are in the enclosed switchyards and are supplied with 33 or 66 kV.
 
ahh, ok, i was thinking of the transformers on the poles, do the pole transformers have that kind of protection? just as a matter of interest, would you happen to know how much a pole transformer would cost?
 
No,
pole TX's have not got that protection and rely on the HT and LT fuses (if fitted) for their protection.

A small 30 kVA may cost NZ$ 3,000, (AU$ 2,700) a 100 kVA around NZ$ 10,000 (AU$ 9,000) plus cost of fitting.
 
OK, i get it! thanks for thatpeople buy these thing to power tesla coils and stuff, that's alot of money!!
 
I don't think tesla coils need that amount of power.

30 KVA is 30 Kilowatts at UPF.

A tesla coil may require 500 VA ,not 30 kVA. unless you building a huge one in a laboratory.

I could be wrong here because i don't work with tesla coils so someone else may have to correct me.

O.T. ? What's the time in Melbourne ? still 3 hours difference ? It's nearly 12 in Auckland ?
 
it's 10am here. i have seen a tesla coil that uses 2 in parallel, but that's the biggest one ever built
 
Wauww !!

But it is not one of us experimenting in the garage of a 240 Volts, 63 Amps domestic supply.

Time for coffee

Cheers

Ray
 
of course we do have pole mounted transformers out in the countryside, where maybe one house or farm is connected to the grid on it's own - just like they do in the US. we just don't use them for entire communities
 
grim said:
of course we do have pole mounted transformers out in the countryside, where maybe one house or farm is connected to the grid on it's own - just like they do in the US. we just don't use them for entire communities
Click to expand...

Yes, I had a look when I was out in the van the other day - but they aren't round!
 
Couldn't resist

The only transformers i use here are for my electronic projects but we do have some high voltage power lines going over the farm. The best thing about the towers is they attract all the lightening and leave the house and shed's alone. Man its an awesum sight watching lightening hit one of the poles and even better watching the next day when the bloke in a chopper weaves inbetween the power lines to find the faults.

Cheers Bryan
 
Pole transformers

Here is one photo from a TX out in the whops.

This one is in a remote area of the Coromandel peninsula, North Island, New Zealand.

Supplying power to a radio transmitter.
50 kVA 11000 Volts S.W.E.R. system.

single wire eath return.

When i take the pics from the pole mounted city TX's i probably open up a new thread so all TX related pics can stay together.
 

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cool!! i want one those things must weigh a ton! ho come the one i walk past everyday doesn't hum?
 
That one on the photo is only a small TX. ( 50 kVA )
It weighs around 400 KG's
Because of the SWER wiring arrangement these are usually mounted on a 2 pole structure.
Similar TX's of the same size or bigger are often mounted on only one pole.
Photo's will be posted.
Regards
Raymond

All transformers in service do hum at 50 or 60 Hz, depends upon in which area of the world you are, Australia is 50 Hz, same as NZ.
It should be audible, unless that transformer is switched off.
Check if the 3 ddo's are in or missing.
 
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i basically stand under the thing, but i still can't hear it??? are they loud? what are ddo's
 
RODALCO said:
Supplying power to a radio transmitter.
50 kVA 11000 Volts S.W.E.R. system.

single wire eath return.
Click to expand...

OK does that mean that there is one overhead wire with 11kv and its return is via "earth" ?? Like the picture below.
I have also attached this pic elsewhere on this board some time ago.

Anyway, I was back in Iceland a couple of weeks ago and had a chance to look at the transformer again.
It is rated 11kv to 230/460volts (cant remember KVA). It is powering a lighthouse on the south coast if Iceland near Vik.

When I examined how it was wired, I was mortified. See the sketch.
Any comments Rodalco? You seem to be well experienced in "big power"!

JimB
 

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  • PolePig Wiring.JPG
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JimB
That is the correct way of connecting a s.w.e.r. system.
There is usually a huge earthbank in the ground to ensure a good earth continuity.
In remote and windy areas it is cheap to run long cables in swer with only one insulator and one wire to deal with. ( no more lineclash problems )
The supply feed in, usually comes via an isolating transformer 11kV 2 phase / 11 kV swer, otherwise the substation feeder or sectionaliser will trip out on eath fault.
The 230 / 460 Volts output is available from the 4 LV terminals.
The phasing is 180° apart.
Connect secondaries in parallel, link X1,X3 and X2,X4 gives 230 V at double the current.
For 460 V link X2 and X3 and earth these, take off from X1 and X4 at 460 volts, to keep line to earth voltages below 250 Volts.

The photo in my post is a 2 phase to 1 phase isolating TX.
I add some more pics in the next couple of days.
 
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